[dev.go2go] README: document that this branch is no longer maintained

For golang/go#46346

Change-Id: Iab050557efb96217477072eca42966662485b6b1
Reviewed-on: https://go-review.googlesource.com/c/go/+/322192
Trust: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

AUTHORS

@@ -195,7 +195,7 @@ Ayanamist Yang <ayanamist@gmail.com>
 Aymerick Jéhanne <aymerick@jehanne.org>
 Azat Kaumov <kaumov.a.r@gmail.com>
 Baiju Muthukadan <baiju.m.mail@gmail.com>
-Baokun Lee <nototon@gmail.com>
+Baokun Lee <nototon@gmail.com> <bk@golangcn.org>
 Bartosz Grzybowski <melkorm@gmail.com>
 Bastian Ike <bastian.ike@gmail.com>
 Ben Burkert <ben@benburkert.com>

CONTRIBUTORS

@@ -321,7 +321,7 @@ Azat Kaumov <kaumov.a.r@gmail.com>
 Baiju Muthukadan <baiju.m.mail@gmail.com>
 Balaram Makam <bmakam.qdt@qualcommdatacenter.com>
 Balazs Lecz <leczb@google.com>
-Baokun Lee <nototon@gmail.com>
+Baokun Lee <nototon@gmail.com> <bk@golangcn.org>
 Barnaby Keene <accounts@southcla.ws>
 Bartosz Grzybowski <melkorm@gmail.com>
 Bartosz Oler <brtsz@google.com>

README.go2go.md

@@ -0,0 +1,46 @@
+# dev.go2go branch
+
+This branch provides an experimental go2go tool for testing the use of
+the generics design draft.
+This branch was published in 2020 and is no longer being maintained.
+The [generics
+proposal](https://go.googlesource.com/proposal/+/refs/heads/master/design/43651-type-parameters.md)
+has [been accepted](https://golang.org/issue/43651) and development is
+now focused on implementing the proposal in the ordinary Go tools.
+
+## Original README
+
+This branch contains a type checker and a translation tool for
+experimentation with generics in Go.
+This implements the [generics design draft](https://go.googlesource.com/proposal/+/refs/heads/master/design/go2draft-type-parameters.md).
+
+You can build this branch [as
+usual](https://golang.org/doc/install/source).
+You can then use the new `go2go` tool.
+Write your generic code in a file with the extension `.go2` instead of
+`.go`.
+Run it using `go tool go2go run x.go2`.
+There are some sample packages in `cmd/go2go/testdata/go2path/src`.
+You can see the full documentation for the tool by running `go doc
+cmd/go2go`.
+
+The `go2go` tool will look for `.go2` files using the environment variable `GO2PATH`.
+You can find some useful packages that you might want to experiment with by
+setting `GO2PATH=$GOROOT/src/cmd/go2go/testdata/go2path`.
+
+If you find bugs in the updated type checker or in the translation
+tool, they should be filed in the [standard Go issue
+tracker](https://golang.org/issue).
+Please start the issue title with `cmd/go2go`.
+Note that the issue tracker should only be used for reporting bugs in
+the tools, not for discussion of changes to the language.
+
+Unlike typical dev branches, we do not intend any eventual merge of
+this code into the master branch.
+We will update it for bug fixes and change to the generic design
+draft.
+If a generics language proposal is accepted, it will be implemented in
+the standard compiler, not via a translation tool.
+The necessary changes to the go/* packages (go/ast, go/parser, and so
+forth) may re-use code from this prototype but will follow the usual
+code review process.

codereview.cfg

@@ -1,2 +1,2 @@
-branch: dev.regabi
-parent-branch: master
+branch: dev.go2go
+parent-branch: master

doc/go1.17.html

@@ -0,0 +1,92 @@
+<!--{
+	"Title": "Go 1.17 Release Notes",
+	"Path":  "/doc/go1.17"
+}-->
+
+<!--
+NOTE: In this document and others in this directory, the convention is to
+set fixed-width phrases with non-fixed-width spaces, as in
+<code>hello</code> <code>world</code>.
+Do not send CLs removing the interior tags from such phrases.
+-->
+
+<style>
+  main ul li { margin: 0.5em 0; }
+</style>
+
+<h2 id="introduction">DRAFT RELEASE NOTES — Introduction to Go 1.17</h2>
+
+<p>
+  <strong>
+    Go 1.17 is not yet released. These are work-in-progress
+    release notes. Go 1.17 is expected to be released in August 2021.
+  </strong>
+</p>
+
+<h2 id="language">Changes to the language</h2>
+
+<p>
+  TODO: complete this section
+</p>
+
+<h2 id="ports">Ports</h2>
+
+<p>
+  TODO: complete this section, or delete if not needed
+</p>
+
+<h2 id="tools">Tools</h2>
+
+<p>
+  TODO: complete this section, or delete if not needed
+</p>
+
+<h3 id="go-command">Go command</h3>
+
+<h4 id="go-get"><code>go</code> <code>get</code></h4>
+
+<p><!-- golang.org/issue/37519 -->
+  The <code>go</code> <code>get</code> <code>-insecure</code> flag is
+  deprecated and has been removed. To permit the use of insecure schemes
+  when fetching dependencies, please use the <code>GOINSECURE</code>
+  environment variable. The <code>-insecure</code> flag also bypassed module
+  sum validation, use <code>GOPRIVATE</code> or <code>GONOSUMDB</code> if
+  you need that functionality. See <code>go</code> <code>help</code>
+  <code>environment</code> for details.
+</p>
+
+<h2 id="runtime">Runtime</h2>
+
+<p>
+  TODO: complete this section, or delete if not needed
+</p>
+
+<h2 id="compiler">Compiler</h2>
+
+<p>
+  TODO: complete this section, or delete if not needed
+</p>
+
+<h2 id="linker">Linker</h2>
+
+<p>
+  TODO: complete this section, or delete if not needed
+</p>
+
+<h2 id="library">Core library</h2>
+
+<p>
+  TODO: complete this section
+</p>
+
+<h3 id="minor_library_changes">Minor changes to the library</h3>
+
+<p>
+  As always, there are various minor changes and updates to the library,
+  made with the Go 1 <a href="/doc/go1compat">promise of compatibility</a>
+  in mind.
+</p>
+
+<p>
+  TODO: complete this section
+</p>

doc/go_spec.html

@@ -1,6 +1,6 @@
 <!--{
 	"Title": "The Go Programming Language Specification",
-	"Subtitle": "Version of Feb 10, 2021",
+	"Subtitle": "Version of Feb 24, 2021",
 	"Path": "/ref/spec"
 }-->
 
@@ -830,7 +830,7 @@ The underlying type of <code>[]B1</code>, <code>B3</code>, and <code>B4</code> i
 
 <h3 id="Method_sets">Method sets</h3>
 <p>
-A type may have a <i>method set</i> associated with it.
+A type has a (possibly empty) <i>method set</i> associated with it.
 The method set of an <a href="#Interface_types">interface type</a> is its interface.
 The method set of any other type <code>T</code> consists of all
 <a href="#Method_declarations">methods</a> declared with receiver type <code>T</code>.
@@ -3532,9 +3532,9 @@ within <code>Greeting</code>, <code>who</code> will have the value
 </p>
 
 <p>
-If the final argument is assignable to a slice type <code>[]T</code>, it is
-passed unchanged as the value for a <code>...T</code> parameter if the argument
-is followed by <code>...</code>. In this case no new slice is created.
+If the final argument is assignable to a slice type <code>[]T</code> and
+is followed by <code>...</code>, it is passed unchanged as the value
+for a <code>...T</code> parameter. In this case no new slice is created.
 </p>
 
 <p>

misc/cgo/test/callback.go

@@ -182,7 +182,7 @@ func testCallbackCallers(t *testing.T) {
 		"runtime.cgocallbackg1",
 		"runtime.cgocallbackg",
 		"runtime.cgocallback",
-		"runtime.asmcgocall",
+		"runtime.systemstack_switch",
 		"runtime.cgocall",
 		"test._Cfunc_callback",
 		"test.nestedCall.func1",

misc/cgo/test/testdata/issue9400/asm_386.s

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !gccgo
+// +build gc
 
 #include "textflag.h"
 

misc/cgo/test/testdata/issue9400/asm_amd64x.s

@@ -3,7 +3,7 @@
 // license that can be found in the LICENSE file.
 
 // +build amd64 amd64p32
-// +build !gccgo
+// +build gc
 
 #include "textflag.h"
 

misc/cgo/test/testdata/issue9400/asm_arm.s

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !gccgo
+// +build gc
 
 #include "textflag.h"
 

misc/cgo/test/testdata/issue9400/asm_arm64.s

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !gccgo
+// +build gc
 
 #include "textflag.h"
 

misc/cgo/test/testdata/issue9400/asm_mips64x.s

@@ -3,7 +3,7 @@
 // license that can be found in the LICENSE file.
 
 // +build mips64 mips64le
-// +build !gccgo
+// +build gc
 
 #include "textflag.h"
 

misc/cgo/test/testdata/issue9400/asm_mipsx.s

@@ -3,7 +3,7 @@
 // license that can be found in the LICENSE file.
 
 // +build mips mipsle
-// +build !gccgo
+// +build gc
 
 #include "textflag.h"
 

misc/cgo/test/testdata/issue9400/asm_ppc64x.s

@@ -3,7 +3,7 @@
 // license that can be found in the LICENSE file.
 
 // +build ppc64 ppc64le
-// +build !gccgo
+// +build gc
 
 #include "textflag.h"
 

misc/cgo/test/testdata/issue9400/asm_riscv64.s

@@ -3,7 +3,7 @@
 // license that can be found in the LICENSE file.
 
 // +build riscv64
-// +build !gccgo
+// +build gc
 
 #include "textflag.h"
 

misc/cgo/test/testdata/issue9400/asm_s390x.s

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !gccgo
+// +build gc
 
 #include "textflag.h"
 

misc/cgo/testplugin/plugin_test.go

@@ -201,12 +201,11 @@ func TestMethod(t *testing.T) {
 	// Exported symbol's method must be live.
 	goCmd(t, "build", "-buildmode=plugin", "-o", "plugin.so", "./method/plugin.go")
 	goCmd(t, "build", "-o", "method.exe", "./method/main.go")
-
-	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
-	defer cancel()
-	cmd := exec.CommandContext(ctx, "./method.exe")
-	out, err := cmd.CombinedOutput()
-	if err != nil {
-		t.Fatalf("%s: %v\n%s", strings.Join(cmd.Args, " "), err, out)
-	}
+	run(t, "./method.exe")
+}
+
+func TestMethod2(t *testing.T) {
+	goCmd(t, "build", "-buildmode=plugin", "-o", "method2.so", "./method2/plugin.go")
+	goCmd(t, "build", "-o", "method2.exe", "./method2/main.go")
+	run(t, "./method2.exe")
 }

misc/cgo/testplugin/testdata/method2/main.go

@@ -0,0 +1,32 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// A type can be passed to a plugin and converted to interface
+// there. So its methods need to be live.
+
+package main
+
+import (
+	"plugin"
+
+	"testplugin/method2/p"
+)
+
+var t p.T
+
+type I interface { M() }
+
+func main() {
+	pl, err := plugin.Open("method2.so")
+	if err != nil {
+		panic(err)
+	}
+
+	f, err := pl.Lookup("F")
+	if err != nil {
+		panic(err)
+	}
+
+	f.(func(p.T) interface{})(t).(I).M()
+}

misc/cgo/testplugin/testdata/method2/p/p.go

@@ -0,0 +1,9 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+type T int
+
+func (T) M() { println("M") }

misc/cgo/testplugin/testdata/method2/plugin.go

@@ -0,0 +1,11 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import "testplugin/method2/p"
+
+func main() {}
+
+func F(t p.T) interface{} { return t }

misc/cgo/testshared/testdata/depBase/asm.s

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !gccgo
+// +build gc
 
 #include "textflag.h"
 

misc/cgo/testshared/testdata/depBase/stubs.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !gccgo
+// +build gc
 
 package depBase
 

src/archive/tar/stat_actime1.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build aix || linux || dragonfly || openbsd || solaris
 // +build aix linux dragonfly openbsd solaris
 
 package tar

src/archive/tar/stat_actime2.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build darwin || freebsd || netbsd
 // +build darwin freebsd netbsd
 
 package tar

src/archive/tar/stat_unix.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build aix || linux || darwin || dragonfly || freebsd || openbsd || netbsd || solaris
 // +build aix linux darwin dragonfly freebsd openbsd netbsd solaris
 
 package tar

src/bufio/bufio.go

@@ -670,7 +670,8 @@ func (b *Writer) WriteByte(c byte) error {
 // WriteRune writes a single Unicode code point, returning
 // the number of bytes written and any error.
 func (b *Writer) WriteRune(r rune) (size int, err error) {
-	if r < utf8.RuneSelf {
+	// Compare as uint32 to correctly handle negative runes.
+	if uint32(r) < utf8.RuneSelf {
 		err = b.WriteByte(byte(r))
 		if err != nil {
 			return 0, err

src/bufio/bufio_test.go

@@ -534,6 +534,20 @@ func TestReadWriteRune(t *testing.T) {
 	}
 }
 
+func TestWriteInvalidRune(t *testing.T) {
+	// Invalid runes, including negative ones, should be written as the
+	// replacement character.
+	for _, r := range []rune{-1, utf8.MaxRune + 1} {
+		var buf bytes.Buffer
+		w := NewWriter(&buf)
+		w.WriteRune(r)
+		w.Flush()
+		if s := buf.String(); s != "\uFFFD" {
+			t.Errorf("WriteRune(%d) wrote %q, not replacement character", r, s)
+		}
+	}
+}
+
 func TestReadStringAllocs(t *testing.T) {
 	r := strings.NewReader("       foo       foo        42        42        42        42        42        42        42        42       4.2       4.2       4.2       4.2\n")
 	buf := NewReader(r)

src/bytes/boundary_test.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 //
+//go:build linux
 // +build linux
 
 package bytes_test

src/bytes/buffer.go

@@ -275,7 +275,8 @@ func (b *Buffer) WriteByte(c byte) error {
 // included to match bufio.Writer's WriteRune. The buffer is grown as needed;
 // if it becomes too large, WriteRune will panic with ErrTooLarge.
 func (b *Buffer) WriteRune(r rune) (n int, err error) {
-	if r < utf8.RuneSelf {
+	// Compare as uint32 to correctly handle negative runes.
+	if uint32(r) < utf8.RuneSelf {
 		b.WriteByte(byte(r))
 		return 1, nil
 	}

src/bytes/buffer_test.go

@@ -6,6 +6,7 @@ package bytes_test
 
 import (
 	. "bytes"
+	"fmt"
 	"io"
 	"math/rand"
 	"testing"
@@ -387,6 +388,16 @@ func TestRuneIO(t *testing.T) {
 	}
 }
 
+func TestWriteInvalidRune(t *testing.T) {
+	// Invalid runes, including negative ones, should be written as
+	// utf8.RuneError.
+	for _, r := range []rune{-1, utf8.MaxRune + 1} {
+		var buf Buffer
+		buf.WriteRune(r)
+		check(t, fmt.Sprintf("TestWriteInvalidRune (%d)", r), &buf, "\uFFFD")
+	}
+}
+
 func TestNext(t *testing.T) {
 	b := []byte{0, 1, 2, 3, 4}
 	tmp := make([]byte, 5)

src/cmd/api/run.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build ignore
 // +build ignore
 
 // The run program is invoked via the dist tool.

src/cmd/asm/internal/asm/asm.go

@@ -811,10 +811,7 @@ func (p *Parser) asmInstruction(op obj.As, cond string, a []obj.Addr) {
 			} else {
 				mask = (^uint32(0) >> uint(mask2+1)) & (^uint32(0) << uint(31-(mask1-1)))
 			}
-			prog.SetFrom3(obj.Addr{
-				Type:   obj.TYPE_CONST,
-				Offset: int64(mask),
-			})
+			prog.SetFrom3Const(int64(mask))
 			prog.To = a[4]
 			break
 		}

src/cmd/asm/internal/asm/endtoend_test.go

@@ -36,6 +36,7 @@ func testEndToEnd(t *testing.T, goarch, file string) {
 	var ok bool
 	testOut = new(bytes.Buffer) // The assembler writes test output to this buffer.
 	ctxt.Bso = bufio.NewWriter(os.Stdout)
+	ctxt.IsAsm = true
 	defer ctxt.Bso.Flush()
 	failed := false
 	ctxt.DiagFunc = func(format string, args ...interface{}) {
@@ -278,6 +279,7 @@ func testErrors(t *testing.T, goarch, file string) {
 	var ok bool
 	testOut = new(bytes.Buffer) // The assembler writes test output to this buffer.
 	ctxt.Bso = bufio.NewWriter(os.Stdout)
+	ctxt.IsAsm = true
 	defer ctxt.Bso.Flush()
 	failed := false
 	var errBuf bytes.Buffer
@@ -437,8 +439,12 @@ func TestPPC64EndToEnd(t *testing.T) {
 	testEndToEnd(t, "ppc64", "ppc64")
 }
 
-func TestRISCVEncoder(t *testing.T) {
-	testEndToEnd(t, "riscv64", "riscvenc")
+func TestRISCVEndToEnd(t *testing.T) {
+	testEndToEnd(t, "riscv64", "riscv64")
+}
+
+func TestRISCVErrors(t *testing.T) {
+	testErrors(t, "riscv64", "riscv64error")
 }
 
 func TestS390XEndToEnd(t *testing.T) {

src/cmd/asm/internal/asm/testdata/riscv64error.s

@@ -0,0 +1,14 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+TEXT errors(SB),$0
+	MOV	$0, 0(SP)			// ERROR "constant load must target register"
+	MOV	$0, 8(SP)			// ERROR "constant load must target register"
+	MOV	$1234, 0(SP)			// ERROR "constant load must target register"
+	MOV	$1234, 8(SP)			// ERROR "constant load must target register"
+	MOVB	$1, X5				// ERROR "unsupported constant load"
+	MOVH	$1, X5				// ERROR "unsupported constant load"
+	MOVW	$1, X5				// ERROR "unsupported constant load"
+	MOVF	$1, X5				// ERROR "unsupported constant load"
+	RET

src/cmd/asm/internal/flags/flags.go

@@ -32,11 +32,13 @@ var (
 	D        MultiFlag
 	I        MultiFlag
 	PrintOut int
+	DebugV   bool
 )
 
 func init() {
 	flag.Var(&D, "D", "predefined symbol with optional simple value -D=identifier=value; can be set multiple times")
 	flag.Var(&I, "I", "include directory; can be set multiple times")
+	flag.BoolVar(&DebugV, "v", false, "print debug output")
 	objabi.AddVersionFlag() // -V
 	objabi.Flagcount("S", "print assembly and machine code", &PrintOut)
 }

src/cmd/asm/main.go

@@ -36,6 +36,7 @@ func main() {
 
 	ctxt := obj.Linknew(architecture.LinkArch)
 	ctxt.Debugasm = flags.PrintOut
+	ctxt.Debugvlog = flags.DebugV
 	ctxt.Flag_dynlink = *flags.Dynlink
 	ctxt.Flag_linkshared = *flags.Linkshared
 	ctxt.Flag_shared = *flags.Shared || *flags.Dynlink

src/cmd/cgo/gcc.go

@@ -1566,9 +1566,17 @@ func (p *Package) gccMachine() []string {
 	case "s390x":
 		return []string{"-m64"}
 	case "mips64", "mips64le":
-		return []string{"-mabi=64"}
+		if gomips64 == "hardfloat" {
+			return []string{"-mabi=64", "-mhard-float"}
+		} else if gomips64 == "softfloat" {
+			return []string{"-mabi=64", "-msoft-float"}
+		}
 	case "mips", "mipsle":
-		return []string{"-mabi=32"}
+		if gomips == "hardfloat" {
+			return []string{"-mabi=32", "-mfp32", "-mhard-float", "-mno-odd-spreg"}
+		} else if gomips == "softfloat" {
+			return []string{"-mabi=32", "-msoft-float"}
+		}
 	}
 	return nil
 }

src/cmd/cgo/main.go

@@ -245,7 +245,7 @@ var importRuntimeCgo = flag.Bool("import_runtime_cgo", true, "import runtime/cgo
 var importSyscall = flag.Bool("import_syscall", true, "import syscall in generated code")
 var trimpath = flag.String("trimpath", "", "applies supplied rewrites or trims prefixes to recorded source file paths")
 
-var goarch, goos string
+var goarch, goos, gomips, gomips64 string
 
 func main() {
 	objabi.AddVersionFlag() // -V
@@ -405,6 +405,8 @@ func newPackage(args []string) *Package {
 	if s := os.Getenv("GOOS"); s != "" {
 		goos = s
 	}
+	gomips = objabi.GOMIPS
+	gomips64 = objabi.GOMIPS64
 	ptrSize := ptrSizeMap[goarch]
 	if ptrSize == 0 {
 		fatalf("unknown ptrSize for $GOARCH %q", goarch)

src/cmd/compile/internal-abi.md

@@ -153,6 +153,7 @@ Assigning a receiver, argument, or result V of underlying type T works
 as follows:
 
 1. Remember I and FP.
+1. If T has zero size, add T to the stack sequence S and return.
 1. Try to register-assign V.
 1. If step 2 failed, reset I and FP to the values from step 1, add T
    to the stack sequence S, and assign V to this field in S.
@@ -295,6 +296,15 @@ An architecture may still define register meanings that aren’t
 compatible with ABI0, but these differences should be easy to account
 for in the compiler.
 
+The assignment algorithm assigns zero-sized values to the stack
+(assignment step 2) in order to support ABI0-equivalence.
+While these values take no space themselves, they do result in
+alignment padding on the stack in ABI0.
+Without this step, the internal ABI would register-assign zero-sized
+values even on architectures that provide no argument registers
+because they don't consume any registers, and hence not add alignment
+padding to the stack.
+
 The algorithm reserves spill space for arguments in the caller’s frame
 so that the compiler can generate a stack growth path that spills into
 this reserved space.
@@ -402,9 +412,6 @@ Special-purpose registers are as follows:
 | R15 | GOT reference temporary | Fixed if dynlink |
 | X15 | Zero value | Fixed |
 
-TODO: We may start with the existing TLS-based g and move to R14
-later.
-
 *Rationale*: These register meanings are compatible with Go’s
 stack-based calling convention except for R14 and X15, which will have
 to be restored on transitions from ABI0 code to ABIInternal code.
@@ -455,13 +462,12 @@ The arithmetic status flags are treated like scratch registers and not
 preserved across calls.
 All other bits in RFLAGS are system flags.
 
-The CPU is always in MMX technology state (not x87 mode).
+At function calls and returns, the CPU is in x87 mode (not MMX
+technology mode).
 
-*Rationale*: Go on amd64 uses the XMM registers and never uses the x87
-registers, so it makes sense to assume the CPU is in MMX mode.
-Otherwise, any function that used the XMM registers would have to
-execute an EMMS instruction before calling another function or
-returning (this is the case in the SysV ABI).
+*Rationale*: Go on amd64 does not use either the x87 registers or MMX
+registers. Hence, we follow the SysV platform conventions in order to
+simplify transitions to and from the C ABI.
 
 At calls, the MXCSR control bits are always set as follows:
 

src/cmd/compile/internal/abi/abiutils.go

@@ -27,9 +27,15 @@ type ABIParamResultInfo struct {
 	outparams         []ABIParamAssignment
 	offsetToSpillArea int64
 	spillAreaSize     int64
+	inRegistersUsed   int
+	outRegistersUsed  int
 	config            *ABIConfig // to enable String() method
 }
 
+func (a *ABIParamResultInfo) Config() *ABIConfig {
+	return a.config
+}
+
 func (a *ABIParamResultInfo) InParams() []ABIParamAssignment {
 	return a.inparams
 }
@@ -38,12 +44,20 @@ func (a *ABIParamResultInfo) OutParams() []ABIParamAssignment {
 	return a.outparams
 }
 
-func (a *ABIParamResultInfo) InParam(i int) ABIParamAssignment {
-	return a.inparams[i]
+func (a *ABIParamResultInfo) InRegistersUsed() int {
+	return a.inRegistersUsed
 }
 
-func (a *ABIParamResultInfo) OutParam(i int) ABIParamAssignment {
-	return a.outparams[i]
+func (a *ABIParamResultInfo) OutRegistersUsed() int {
+	return a.outRegistersUsed
+}
+
+func (a *ABIParamResultInfo) InParam(i int) *ABIParamAssignment {
+	return &a.inparams[i]
+}
+
+func (a *ABIParamResultInfo) OutParam(i int) *ABIParamAssignment {
+	return &a.outparams[i]
 }
 
 func (a *ABIParamResultInfo) SpillAreaOffset() int64 {
@@ -68,10 +82,11 @@ type RegIndex uint8
 // ABIParamAssignment holds information about how a specific param or
 // result will be passed: in registers (in which case 'Registers' is
 // populated) or on the stack (in which case 'Offset' is set to a
-// non-negative stack offset. The values in 'Registers' are indices (as
-// described above), not architected registers.
+// non-negative stack offset. The values in 'Registers' are indices
+// (as described above), not architected registers.
 type ABIParamAssignment struct {
 	Type      *types.Type
+	Name      types.Object // should always be *ir.Name, used to match with a particular ssa.OpArg.
 	Registers []RegIndex
 	offset    int32
 }
@@ -96,6 +111,18 @@ func (a *ABIParamAssignment) SpillOffset() int32 {
 	return a.offset
 }
 
+// FrameOffset returns the location that a value would spill to, if any exists.
+// For register-allocated inputs, that is their spill offset reserved for morestack
+// (might as well use it, it is there); for stack-allocated inputs and outputs,
+// that is their location on the stack.  For register-allocated outputs, there is
+// no defined spill area, so return -1.
+func (a *ABIParamAssignment) FrameOffset(i *ABIParamResultInfo) int64 {
+	if len(a.Registers) == 0 || a.offset == -1 {
+		return int64(a.offset)
+	}
+	return int64(a.offset) + i.SpillAreaOffset()
+}
+
 // RegAmounts holds a specified number of integer/float registers.
 type RegAmounts struct {
 	intRegs   int
@@ -106,94 +133,216 @@ type RegAmounts struct {
 // by the ABI rules for parameter passing and result returning.
 type ABIConfig struct {
 	// Do we need anything more than this?
+	offsetForLocals  int64 // e.g., obj.(*Link).FixedFrameSize() -- extra linkage information on some architectures.
 	regAmounts       RegAmounts
 	regsForTypeCache map[*types.Type]int
 }
 
 // NewABIConfig returns a new ABI configuration for an architecture with
 // iRegsCount integer/pointer registers and fRegsCount floating point registers.
-func NewABIConfig(iRegsCount, fRegsCount int) *ABIConfig {
-	return &ABIConfig{regAmounts: RegAmounts{iRegsCount, fRegsCount}, regsForTypeCache: make(map[*types.Type]int)}
+func NewABIConfig(iRegsCount, fRegsCount int, offsetForLocals int64) *ABIConfig {
+	return &ABIConfig{offsetForLocals: offsetForLocals, regAmounts: RegAmounts{iRegsCount, fRegsCount}, regsForTypeCache: make(map[*types.Type]int)}
+}
+
+// Copy returns a copy of an ABIConfig for use in a function's compilation so that access to the cache does not need to be protected with a mutex.
+func (a *ABIConfig) Copy() *ABIConfig {
+	b := *a
+	b.regsForTypeCache = make(map[*types.Type]int)
+	return &b
+}
+
+// LocalsOffset returns the architecture-dependent offset from SP for args and results.
+// In theory this is only used for debugging; it ought to already be incorporated into
+// results from the ABI-related methods
+func (a *ABIConfig) LocalsOffset() int64 {
+	return a.offsetForLocals
+}
+
+// FloatIndexFor translates r into an index in the floating point parameter
+// registers.  If the result is negative, the input index was actually for the
+// integer parameter registers.
+func (a *ABIConfig) FloatIndexFor(r RegIndex) int64 {
+	return int64(r) - int64(a.regAmounts.intRegs)
 }
 
 // NumParamRegs returns the number of parameter registers used for a given type,
 // without regard for the number available.
 func (a *ABIConfig) NumParamRegs(t *types.Type) int {
+	var n int
 	if n, ok := a.regsForTypeCache[t]; ok {
 		return n
 	}
 
 	if t.IsScalar() || t.IsPtrShaped() {
-		var n int
 		if t.IsComplex() {
 			n = 2
 		} else {
 			n = (int(t.Size()) + types.RegSize - 1) / types.RegSize
 		}
-		a.regsForTypeCache[t] = n
-		return n
-	}
-	typ := t.Kind()
-	n := 0
-	switch typ {
-	case types.TARRAY:
-		n = a.NumParamRegs(t.Elem()) * int(t.NumElem())
-	case types.TSTRUCT:
-		for _, f := range t.FieldSlice() {
-			n += a.NumParamRegs(f.Type)
+	} else {
+		typ := t.Kind()
+		switch typ {
+		case types.TARRAY:
+			n = a.NumParamRegs(t.Elem()) * int(t.NumElem())
+		case types.TSTRUCT:
+			for _, f := range t.FieldSlice() {
+				n += a.NumParamRegs(f.Type)
+			}
+		case types.TSLICE:
+			n = a.NumParamRegs(synthSlice)
+		case types.TSTRING:
+			n = a.NumParamRegs(synthString)
+		case types.TINTER:
+			n = a.NumParamRegs(synthIface)
 		}
-	case types.TSLICE:
-		n = a.NumParamRegs(synthSlice)
-	case types.TSTRING:
-		n = a.NumParamRegs(synthString)
-	case types.TINTER:
-		n = a.NumParamRegs(synthIface)
 	}
 	a.regsForTypeCache[t] = n
+
 	return n
 }
 
-// ABIAnalyze takes a function type 't' and an ABI rules description
+// preAllocateParams gets the slice sizes right for inputs and outputs.
+func (a *ABIParamResultInfo) preAllocateParams(hasRcvr bool, nIns, nOuts int) {
+	if hasRcvr {
+		nIns++
+	}
+	a.inparams = make([]ABIParamAssignment, 0, nIns)
+	a.outparams = make([]ABIParamAssignment, 0, nOuts)
+}
+
+// ABIAnalyzeTypes takes an optional receiver type, arrays of ins and outs, and returns an ABIParamResultInfo,
+// based on the given configuration.  This is the same result computed by config.ABIAnalyze applied to the
+// corresponding method/function type, except that all the embedded parameter names are nil.
+// This is intended for use by ssagen/ssa.go:(*state).rtcall, for runtime functions that lack a parsed function type.
+func (config *ABIConfig) ABIAnalyzeTypes(rcvr *types.Type, ins, outs []*types.Type) *ABIParamResultInfo {
+	setup()
+	s := assignState{
+		stackOffset: config.offsetForLocals,
+		rTotal:      config.regAmounts,
+	}
+	result := &ABIParamResultInfo{config: config}
+	result.preAllocateParams(rcvr != nil, len(ins), len(outs))
+
+	// Receiver
+	if rcvr != nil {
+		result.inparams = append(result.inparams,
+			s.assignParamOrReturn(rcvr, nil, false))
+	}
+
+	// Inputs
+	for _, t := range ins {
+		result.inparams = append(result.inparams,
+			s.assignParamOrReturn(t, nil, false))
+	}
+	s.stackOffset = types.Rnd(s.stackOffset, int64(types.RegSize))
+	result.inRegistersUsed = s.rUsed.intRegs + s.rUsed.floatRegs
+
+	// Outputs
+	s.rUsed = RegAmounts{}
+	for _, t := range outs {
+		result.outparams = append(result.outparams, s.assignParamOrReturn(t, nil, true))
+	}
+	// The spill area is at a register-aligned offset and its size is rounded up to a register alignment.
+	// TODO in theory could align offset only to minimum required by spilled data types.
+	result.offsetToSpillArea = alignTo(s.stackOffset, types.RegSize)
+	result.spillAreaSize = alignTo(s.spillOffset, types.RegSize)
+	result.outRegistersUsed = s.rUsed.intRegs + s.rUsed.floatRegs
+
+	return result
+}
+
+// ABIAnalyzeFuncType takes a function type 'ft' and an ABI rules description
 // 'config' and analyzes the function to determine how its parameters
 // and results will be passed (in registers or on the stack), returning
 // an ABIParamResultInfo object that holds the results of the analysis.
-func (config *ABIConfig) ABIAnalyze(t *types.Type) ABIParamResultInfo {
+func (config *ABIConfig) ABIAnalyzeFuncType(ft *types.Func) *ABIParamResultInfo {
 	setup()
 	s := assignState{
-		rTotal: config.regAmounts,
+		stackOffset: config.offsetForLocals,
+		rTotal:      config.regAmounts,
 	}
-	result := ABIParamResultInfo{config: config}
+	result := &ABIParamResultInfo{config: config}
+	result.preAllocateParams(ft.Receiver != nil, ft.Params.NumFields(), ft.Results.NumFields())
 
 	// Receiver
-	ft := t.FuncType()
-	if t.NumRecvs() != 0 {
-		rfsl := ft.Receiver.FieldSlice()
+	// TODO(register args) ? seems like "struct" and "fields" is not right anymore for describing function parameters
+	if ft.Receiver != nil && ft.Receiver.NumFields() != 0 {
+		r := ft.Receiver.FieldSlice()[0]
 		result.inparams = append(result.inparams,
-			s.assignParamOrReturn(rfsl[0].Type, false))
+			s.assignParamOrReturn(r.Type, r.Nname, false))
 	}
 
 	// Inputs
 	ifsl := ft.Params.FieldSlice()
 	for _, f := range ifsl {
 		result.inparams = append(result.inparams,
-			s.assignParamOrReturn(f.Type, false))
+			s.assignParamOrReturn(f.Type, f.Nname, false))
 	}
 	s.stackOffset = types.Rnd(s.stackOffset, int64(types.RegSize))
+	result.inRegistersUsed = s.rUsed.intRegs + s.rUsed.floatRegs
 
 	// Outputs
 	s.rUsed = RegAmounts{}
 	ofsl := ft.Results.FieldSlice()
 	for _, f := range ofsl {
-		result.outparams = append(result.outparams, s.assignParamOrReturn(f.Type, true))
+		result.outparams = append(result.outparams, s.assignParamOrReturn(f.Type, f.Nname, true))
 	}
 	// The spill area is at a register-aligned offset and its size is rounded up to a register alignment.
 	// TODO in theory could align offset only to minimum required by spilled data types.
 	result.offsetToSpillArea = alignTo(s.stackOffset, types.RegSize)
 	result.spillAreaSize = alignTo(s.spillOffset, types.RegSize)
-
+	result.outRegistersUsed = s.rUsed.intRegs + s.rUsed.floatRegs
 	return result
 }
 
+// ABIAnalyze returns the same result as ABIAnalyzeFuncType, but also
+// updates the offsets of all the receiver, input, and output fields.
+func (config *ABIConfig) ABIAnalyze(t *types.Type) *ABIParamResultInfo {
+	ft := t.FuncType()
+	result := config.ABIAnalyzeFuncType(ft)
+	// Fill in the frame offsets for receiver, inputs, results
+	k := 0
+	if t.NumRecvs() != 0 {
+		config.updateOffset(result, ft.Receiver.FieldSlice()[0], result.inparams[0], false)
+		k++
+	}
+	for i, f := range ft.Params.FieldSlice() {
+		config.updateOffset(result, f, result.inparams[k+i], false)
+	}
+	for i, f := range ft.Results.FieldSlice() {
+		config.updateOffset(result, f, result.outparams[i], true)
+	}
+	return result
+}
+
+// parameterUpdateMu protects the Offset field of function/method parameters (a subset of structure Fields)
+var parameterUpdateMu sync.Mutex
+
+// FieldOffsetOf returns a concurency-safe version of f.Offset
+func FieldOffsetOf(f *types.Field) int64 {
+	parameterUpdateMu.Lock()
+	defer parameterUpdateMu.Unlock()
+	return f.Offset
+}
+
+func (config *ABIConfig) updateOffset(result *ABIParamResultInfo, f *types.Field, a ABIParamAssignment, isReturn bool) {
+	// Everything except return values in registers has either a frame home (if not in a register) or a frame spill location.
+	if !isReturn || len(a.Registers) == 0 {
+		// The type frame offset DOES NOT show effects of minimum frame size.
+		// Getting this wrong breaks stackmaps, see liveness/plive.go:WriteFuncMap and typebits/typebits.go:Set
+		parameterUpdateMu.Lock()
+		defer parameterUpdateMu.Unlock()
+		off := a.FrameOffset(result) - config.LocalsOffset()
+		fOffset := f.Offset
+		if fOffset == types.BOGUS_FUNARG_OFFSET {
+			// Set the Offset the first time. After that, we may recompute it, but it should never change.
+			f.Offset = off
+		} else if fOffset != off {
+			panic(fmt.Errorf("Offset changed from %d to %d", fOffset, off))
+		}
+	}
+}
+
 //......................................................................
 //
 // Non-public portions.
@@ -292,7 +441,7 @@ func (state *assignState) allocateRegs() []RegIndex {
 // regAllocate creates a register ABIParamAssignment object for a param
 // or result with the specified type, as a final step (this assumes
 // that all of the safety/suitability analysis is complete).
-func (state *assignState) regAllocate(t *types.Type, isReturn bool) ABIParamAssignment {
+func (state *assignState) regAllocate(t *types.Type, name types.Object, isReturn bool) ABIParamAssignment {
 	spillLoc := int64(-1)
 	if !isReturn {
 		// Spill for register-resident t must be aligned for storage of a t.
@@ -301,6 +450,7 @@ func (state *assignState) regAllocate(t *types.Type, isReturn bool) ABIParamAssi
 	}
 	return ABIParamAssignment{
 		Type:      t,
+		Name:      name,
 		Registers: state.allocateRegs(),
 		offset:    int32(spillLoc),
 	}
@@ -309,9 +459,10 @@ func (state *assignState) regAllocate(t *types.Type, isReturn bool) ABIParamAssi
 // stackAllocate creates a stack memory ABIParamAssignment object for
 // a param or result with the specified type, as a final step (this
 // assumes that all of the safety/suitability analysis is complete).
-func (state *assignState) stackAllocate(t *types.Type) ABIParamAssignment {
+func (state *assignState) stackAllocate(t *types.Type, name types.Object) ABIParamAssignment {
 	return ABIParamAssignment{
 		Type:   t,
+		Name:   name,
 		offset: int32(state.stackSlot(t)),
 	}
 }
@@ -444,18 +595,18 @@ func (state *assignState) regassign(pt *types.Type) bool {
 }
 
 // assignParamOrReturn processes a given receiver, param, or result
-// of type 'pt' to determine whether it can be register assigned.
+// of field f to determine whether it can be register assigned.
 // The result of the analysis is recorded in the result
 // ABIParamResultInfo held in 'state'.
-func (state *assignState) assignParamOrReturn(pt *types.Type, isReturn bool) ABIParamAssignment {
+func (state *assignState) assignParamOrReturn(pt *types.Type, n types.Object, isReturn bool) ABIParamAssignment {
 	state.pUsed = RegAmounts{}
 	if pt.Width == types.BADWIDTH {
 		panic("should never happen")
 	} else if pt.Width == 0 {
-		return state.stackAllocate(pt)
+		return state.stackAllocate(pt, n)
 	} else if state.regassign(pt) {
-		return state.regAllocate(pt, isReturn)
+		return state.regAllocate(pt, n, isReturn)
 	} else {
-		return state.stackAllocate(pt)
+		return state.stackAllocate(pt, n)
 	}
 }

src/cmd/compile/internal/amd64/ggen.go

@@ -56,8 +56,8 @@ func dzDI(b int64) int64 {
 
 func zerorange(pp *objw.Progs, p *obj.Prog, off, cnt int64, state *uint32) *obj.Prog {
 	const (
-		ax = 1 << iota
-		x0
+		ax  = 1 << iota // if AX is already zeroed.
+		x15             // if X15 is already zeroed. Note: in new ABI, X15 is always zero.
 	)
 
 	if cnt == 0 {
@@ -85,29 +85,29 @@ func zerorange(pp *objw.Progs, p *obj.Prog, off, cnt int64, state *uint32) *obj.
 		}
 		p = pp.Append(p, x86.AMOVQ, obj.TYPE_REG, x86.REG_AX, 0, obj.TYPE_MEM, x86.REG_SP, off)
 	} else if !isPlan9 && cnt <= int64(8*types.RegSize) {
-		if *state&x0 == 0 {
-			p = pp.Append(p, x86.AXORPS, obj.TYPE_REG, x86.REG_X0, 0, obj.TYPE_REG, x86.REG_X0, 0)
-			*state |= x0
+		if objabi.Regabi_enabled == 0 && *state&x15 == 0 {
+			p = pp.Append(p, x86.AXORPS, obj.TYPE_REG, x86.REG_X15, 0, obj.TYPE_REG, x86.REG_X15, 0)
+			*state |= x15
 		}
 
 		for i := int64(0); i < cnt/16; i++ {
-			p = pp.Append(p, x86.AMOVUPS, obj.TYPE_REG, x86.REG_X0, 0, obj.TYPE_MEM, x86.REG_SP, off+i*16)
+			p = pp.Append(p, x86.AMOVUPS, obj.TYPE_REG, x86.REG_X15, 0, obj.TYPE_MEM, x86.REG_SP, off+i*16)
 		}
 
 		if cnt%16 != 0 {
-			p = pp.Append(p, x86.AMOVUPS, obj.TYPE_REG, x86.REG_X0, 0, obj.TYPE_MEM, x86.REG_SP, off+cnt-int64(16))
+			p = pp.Append(p, x86.AMOVUPS, obj.TYPE_REG, x86.REG_X15, 0, obj.TYPE_MEM, x86.REG_SP, off+cnt-int64(16))
 		}
 	} else if !isPlan9 && (cnt <= int64(128*types.RegSize)) {
-		if *state&x0 == 0 {
-			p = pp.Append(p, x86.AXORPS, obj.TYPE_REG, x86.REG_X0, 0, obj.TYPE_REG, x86.REG_X0, 0)
-			*state |= x0
+		if objabi.Regabi_enabled == 0 && *state&x15 == 0 {
+			p = pp.Append(p, x86.AXORPS, obj.TYPE_REG, x86.REG_X15, 0, obj.TYPE_REG, x86.REG_X15, 0)
+			*state |= x15
 		}
 		p = pp.Append(p, leaptr, obj.TYPE_MEM, x86.REG_SP, off+dzDI(cnt), obj.TYPE_REG, x86.REG_DI, 0)
 		p = pp.Append(p, obj.ADUFFZERO, obj.TYPE_NONE, 0, 0, obj.TYPE_ADDR, 0, dzOff(cnt))
 		p.To.Sym = ir.Syms.Duffzero
 
 		if cnt%16 != 0 {
-			p = pp.Append(p, x86.AMOVUPS, obj.TYPE_REG, x86.REG_X0, 0, obj.TYPE_MEM, x86.REG_DI, -int64(8))
+			p = pp.Append(p, x86.AMOVUPS, obj.TYPE_REG, x86.REG_X15, 0, obj.TYPE_MEM, x86.REG_DI, -int64(8))
 		}
 	} else {
 		if *state&ax == 0 {

src/cmd/compile/internal/amd64/ssa.go

@@ -16,6 +16,7 @@ import (
 	"cmd/compile/internal/types"
 	"cmd/internal/obj"
 	"cmd/internal/obj/x86"
+	"cmd/internal/objabi"
 )
 
 // markMoves marks any MOVXconst ops that need to avoid clobbering flags.
@@ -200,10 +201,7 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		p := s.Prog(v.Op.Asm())
 		p.From = obj.Addr{Type: obj.TYPE_REG, Reg: v.Args[2].Reg()}
 		p.To = obj.Addr{Type: obj.TYPE_REG, Reg: v.Reg()}
-		p.SetFrom3(obj.Addr{Type: obj.TYPE_REG, Reg: v.Args[1].Reg()})
-		if v.Reg() != v.Args[0].Reg() {
-			v.Fatalf("input[0] and output not in same register %s", v.LongString())
-		}
+		p.SetFrom3Reg(v.Args[1].Reg())
 	case ssa.OpAMD64ADDQ, ssa.OpAMD64ADDL:
 		r := v.Reg()
 		r1 := v.Args[0].Reg()
@@ -253,11 +251,7 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		ssa.OpAMD64BTSL, ssa.OpAMD64BTSQ,
 		ssa.OpAMD64BTCL, ssa.OpAMD64BTCQ,
 		ssa.OpAMD64BTRL, ssa.OpAMD64BTRQ:
-		r := v.Reg()
-		if r != v.Args[0].Reg() {
-			v.Fatalf("input[0] and output not in same register %s", v.LongString())
-		}
-		opregreg(s, v.Op.Asm(), r, v.Args[1].Reg())
+		opregreg(s, v.Op.Asm(), v.Reg(), v.Args[1].Reg())
 
 	case ssa.OpAMD64DIVQU, ssa.OpAMD64DIVLU, ssa.OpAMD64DIVWU:
 		// Arg[0] (the dividend) is in AX.
@@ -400,20 +394,16 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		// compute (x+y)/2 unsigned.
 		// Do a 64-bit add, the overflow goes into the carry.
 		// Shift right once and pull the carry back into the 63rd bit.
-		r := v.Reg()
-		if r != v.Args[0].Reg() {
-			v.Fatalf("input[0] and output not in same register %s", v.LongString())
-		}
 		p := s.Prog(x86.AADDQ)
 		p.From.Type = obj.TYPE_REG
 		p.To.Type = obj.TYPE_REG
-		p.To.Reg = r
+		p.To.Reg = v.Reg()
 		p.From.Reg = v.Args[1].Reg()
 		p = s.Prog(x86.ARCRQ)
 		p.From.Type = obj.TYPE_CONST
 		p.From.Offset = 1
 		p.To.Type = obj.TYPE_REG
-		p.To.Reg = r
+		p.To.Reg = v.Reg()
 
 	case ssa.OpAMD64ADDQcarry, ssa.OpAMD64ADCQ:
 		r := v.Reg0()
@@ -529,21 +519,13 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		ssa.OpAMD64CMOVQCS, ssa.OpAMD64CMOVLCS, ssa.OpAMD64CMOVWCS,
 		ssa.OpAMD64CMOVQGTF, ssa.OpAMD64CMOVLGTF, ssa.OpAMD64CMOVWGTF,
 		ssa.OpAMD64CMOVQGEF, ssa.OpAMD64CMOVLGEF, ssa.OpAMD64CMOVWGEF:
-		r := v.Reg()
-		if r != v.Args[0].Reg() {
-			v.Fatalf("input[0] and output not in same register %s", v.LongString())
-		}
 		p := s.Prog(v.Op.Asm())
 		p.From.Type = obj.TYPE_REG
 		p.From.Reg = v.Args[1].Reg()
 		p.To.Type = obj.TYPE_REG
-		p.To.Reg = r
+		p.To.Reg = v.Reg()
 
 	case ssa.OpAMD64CMOVQNEF, ssa.OpAMD64CMOVLNEF, ssa.OpAMD64CMOVWNEF:
-		r := v.Reg()
-		if r != v.Args[0].Reg() {
-			v.Fatalf("input[0] and output not in same register %s", v.LongString())
-		}
 		// Flag condition: ^ZERO || PARITY
 		// Generate:
 		//   CMOV*NE  SRC,DST
@@ -552,7 +534,7 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		p.From.Type = obj.TYPE_REG
 		p.From.Reg = v.Args[1].Reg()
 		p.To.Type = obj.TYPE_REG
-		p.To.Reg = r
+		p.To.Reg = v.Reg()
 		var q *obj.Prog
 		if v.Op == ssa.OpAMD64CMOVQNEF {
 			q = s.Prog(x86.ACMOVQPS)
@@ -564,14 +546,9 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		q.From.Type = obj.TYPE_REG
 		q.From.Reg = v.Args[1].Reg()
 		q.To.Type = obj.TYPE_REG
-		q.To.Reg = r
+		q.To.Reg = v.Reg()
 
 	case ssa.OpAMD64CMOVQEQF, ssa.OpAMD64CMOVLEQF, ssa.OpAMD64CMOVWEQF:
-		r := v.Reg()
-		if r != v.Args[0].Reg() {
-			v.Fatalf("input[0] and output not in same register %s", v.LongString())
-		}
-
 		// Flag condition: ZERO && !PARITY
 		// Generate:
 		//   MOV      SRC,AX
@@ -588,7 +565,7 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		}
 		p := s.Prog(v.Op.Asm())
 		p.From.Type = obj.TYPE_REG
-		p.From.Reg = r
+		p.From.Reg = v.Reg()
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = x86.REG_AX
 		var q *obj.Prog
@@ -602,7 +579,7 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		q.From.Type = obj.TYPE_REG
 		q.From.Reg = x86.REG_AX
 		q.To.Type = obj.TYPE_REG
-		q.To.Reg = r
+		q.To.Reg = v.Reg()
 
 	case ssa.OpAMD64MULQconst, ssa.OpAMD64MULLconst:
 		r := v.Reg()
@@ -611,7 +588,7 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		p.From.Offset = v.AuxInt
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = r
-		p.SetFrom3(obj.Addr{Type: obj.TYPE_REG, Reg: v.Args[0].Reg()})
+		p.SetFrom3Reg(v.Args[0].Reg())
 
 	case ssa.OpAMD64SUBQconst, ssa.OpAMD64SUBLconst,
 		ssa.OpAMD64ANDQconst, ssa.OpAMD64ANDLconst,
@@ -621,15 +598,11 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		ssa.OpAMD64SHRQconst, ssa.OpAMD64SHRLconst, ssa.OpAMD64SHRWconst, ssa.OpAMD64SHRBconst,
 		ssa.OpAMD64SARQconst, ssa.OpAMD64SARLconst, ssa.OpAMD64SARWconst, ssa.OpAMD64SARBconst,
 		ssa.OpAMD64ROLQconst, ssa.OpAMD64ROLLconst, ssa.OpAMD64ROLWconst, ssa.OpAMD64ROLBconst:
-		r := v.Reg()
-		if r != v.Args[0].Reg() {
-			v.Fatalf("input[0] and output not in same register %s", v.LongString())
-		}
 		p := s.Prog(v.Op.Asm())
 		p.From.Type = obj.TYPE_CONST
 		p.From.Offset = v.AuxInt
 		p.To.Type = obj.TYPE_REG
-		p.To.Reg = r
+		p.To.Reg = v.Reg()
 	case ssa.OpAMD64SBBQcarrymask, ssa.OpAMD64SBBLcarrymask:
 		r := v.Reg()
 		p := s.Prog(v.Op.Asm())
@@ -845,7 +818,7 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		if s.ABI != obj.ABIInternal {
 			v.Fatalf("MOVOstorezero can be only used in ABIInternal functions")
 		}
-		if !base.Flag.ABIWrap {
+		if !(objabi.Regabi_enabled == 1 && base.Flag.ABIWrap) {
 			// zeroing X15 manually if wrappers are not used
 			opregreg(s, x86.AXORPS, x86.REG_X15, x86.REG_X15)
 		}
@@ -912,9 +885,6 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		ssagen.AddAux(&p.From, v)
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = v.Reg()
-		if v.Reg() != v.Args[0].Reg() {
-			v.Fatalf("input[0] and output not in same register %s", v.LongString())
-		}
 	case ssa.OpAMD64ADDLloadidx1, ssa.OpAMD64ADDLloadidx4, ssa.OpAMD64ADDLloadidx8, ssa.OpAMD64ADDQloadidx1, ssa.OpAMD64ADDQloadidx8,
 		ssa.OpAMD64SUBLloadidx1, ssa.OpAMD64SUBLloadidx4, ssa.OpAMD64SUBLloadidx8, ssa.OpAMD64SUBQloadidx1, ssa.OpAMD64SUBQloadidx8,
 		ssa.OpAMD64ANDLloadidx1, ssa.OpAMD64ANDLloadidx4, ssa.OpAMD64ANDLloadidx8, ssa.OpAMD64ANDQloadidx1, ssa.OpAMD64ANDQloadidx8,
@@ -938,14 +908,11 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		ssagen.AddAux(&p.From, v)
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = v.Reg()
-		if v.Reg() != v.Args[0].Reg() {
-			v.Fatalf("input[0] and output not in same register %s", v.LongString())
-		}
 	case ssa.OpAMD64DUFFZERO:
 		if s.ABI != obj.ABIInternal {
 			v.Fatalf("MOVOconst can be only used in ABIInternal functions")
 		}
-		if !base.Flag.ABIWrap {
+		if !(objabi.Regabi_enabled == 1 && base.Flag.ABIWrap) {
 			// zeroing X15 manually if wrappers are not used
 			opregreg(s, x86.AXORPS, x86.REG_X15, x86.REG_X15)
 		}
@@ -1017,20 +984,20 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		// Closure pointer is DX.
 		ssagen.CheckLoweredGetClosurePtr(v)
 	case ssa.OpAMD64LoweredGetG:
-		if base.Flag.ABIWrap {
+		if objabi.Regabi_enabled == 1 && base.Flag.ABIWrap {
 			v.Fatalf("LoweredGetG should not appear in new ABI")
 		}
 		r := v.Reg()
 		getgFromTLS(s, r)
 	case ssa.OpAMD64CALLstatic:
-		if s.ABI == obj.ABI0 && v.Aux.(*ssa.AuxCall).Fn.ABI() == obj.ABIInternal {
+		if objabi.Regabi_enabled == 1 && s.ABI == obj.ABI0 && v.Aux.(*ssa.AuxCall).Fn.ABI() == obj.ABIInternal {
 			// zeroing X15 when entering ABIInternal from ABI0
 			opregreg(s, x86.AXORPS, x86.REG_X15, x86.REG_X15)
 			// set G register from TLS
 			getgFromTLS(s, x86.REG_R14)
 		}
 		s.Call(v)
-		if s.ABI == obj.ABIInternal && v.Aux.(*ssa.AuxCall).Fn.ABI() == obj.ABI0 {
+		if objabi.Regabi_enabled == 1 && s.ABI == obj.ABIInternal && v.Aux.(*ssa.AuxCall).Fn.ABI() == obj.ABI0 {
 			// zeroing X15 when entering ABIInternal from ABI0
 			opregreg(s, x86.AXORPS, x86.REG_X15, x86.REG_X15)
 			// set G register from TLS
@@ -1077,24 +1044,16 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 	case ssa.OpAMD64NEGQ, ssa.OpAMD64NEGL,
 		ssa.OpAMD64BSWAPQ, ssa.OpAMD64BSWAPL,
 		ssa.OpAMD64NOTQ, ssa.OpAMD64NOTL:
-		r := v.Reg()
-		if r != v.Args[0].Reg() {
-			v.Fatalf("input[0] and output not in same register %s", v.LongString())
-		}
 		p := s.Prog(v.Op.Asm())
 		p.To.Type = obj.TYPE_REG
-		p.To.Reg = r
+		p.To.Reg = v.Reg()
 
 	case ssa.OpAMD64NEGLflags:
-		r := v.Reg0()
-		if r != v.Args[0].Reg() {
-			v.Fatalf("input[0] and output not in same register %s", v.LongString())
-		}
 		p := s.Prog(v.Op.Asm())
 		p.To.Type = obj.TYPE_REG
-		p.To.Reg = r
+		p.To.Reg = v.Reg0()
 
-	case ssa.OpAMD64BSFQ, ssa.OpAMD64BSRQ, ssa.OpAMD64BSFL, ssa.OpAMD64BSRL, ssa.OpAMD64SQRTSD:
+	case ssa.OpAMD64BSFQ, ssa.OpAMD64BSRQ, ssa.OpAMD64BSFL, ssa.OpAMD64BSRL, ssa.OpAMD64SQRTSD, ssa.OpAMD64SQRTSS:
 		p := s.Prog(v.Op.Asm())
 		p.From.Type = obj.TYPE_REG
 		p.From.Reg = v.Args[0].Reg()
@@ -1102,7 +1061,7 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		switch v.Op {
 		case ssa.OpAMD64BSFQ, ssa.OpAMD64BSRQ:
 			p.To.Reg = v.Reg0()
-		case ssa.OpAMD64BSFL, ssa.OpAMD64BSRL, ssa.OpAMD64SQRTSD:
+		case ssa.OpAMD64BSFL, ssa.OpAMD64BSRL, ssa.OpAMD64SQRTSD, ssa.OpAMD64SQRTSS:
 			p.To.Reg = v.Reg()
 		}
 	case ssa.OpAMD64ROUNDSD:
@@ -1114,7 +1073,7 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		}
 		p.From.Offset = val
 		p.From.Type = obj.TYPE_CONST
-		p.SetFrom3(obj.Addr{Type: obj.TYPE_REG, Reg: v.Args[0].Reg()})
+		p.SetFrom3Reg(v.Args[0].Reg())
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = v.Reg()
 	case ssa.OpAMD64POPCNTQ, ssa.OpAMD64POPCNTL:
@@ -1213,25 +1172,17 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = v.Reg0()
 	case ssa.OpAMD64XCHGB, ssa.OpAMD64XCHGL, ssa.OpAMD64XCHGQ:
-		r := v.Reg0()
-		if r != v.Args[0].Reg() {
-			v.Fatalf("input[0] and output[0] not in same register %s", v.LongString())
-		}
 		p := s.Prog(v.Op.Asm())
 		p.From.Type = obj.TYPE_REG
-		p.From.Reg = r
+		p.From.Reg = v.Reg0()
 		p.To.Type = obj.TYPE_MEM
 		p.To.Reg = v.Args[1].Reg()
 		ssagen.AddAux(&p.To, v)
 	case ssa.OpAMD64XADDLlock, ssa.OpAMD64XADDQlock:
-		r := v.Reg0()
-		if r != v.Args[0].Reg() {
-			v.Fatalf("input[0] and output[0] not in same register %s", v.LongString())
-		}
 		s.Prog(x86.ALOCK)
 		p := s.Prog(v.Op.Asm())
 		p.From.Type = obj.TYPE_REG
-		p.From.Reg = r
+		p.From.Reg = v.Reg0()
 		p.To.Type = obj.TYPE_MEM
 		p.To.Reg = v.Args[1].Reg()
 		ssagen.AddAux(&p.To, v)
@@ -1333,7 +1284,7 @@ func ssaGenBlock(s *ssagen.State, b, next *ssa.Block) {
 	case ssa.BlockRet:
 		s.Prog(obj.ARET)
 	case ssa.BlockRetJmp:
-		if s.ABI == obj.ABI0 && b.Aux.(*obj.LSym).ABI() == obj.ABIInternal {
+		if objabi.Regabi_enabled == 1 && s.ABI == obj.ABI0 && b.Aux.(*obj.LSym).ABI() == obj.ABIInternal {
 			// zeroing X15 when entering ABIInternal from ABI0
 			opregreg(s, x86.AXORPS, x86.REG_X15, x86.REG_X15)
 			// set G register from TLS

src/cmd/compile/internal/arm/ssa.go

@@ -173,9 +173,6 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = y
 	case ssa.OpARMMOVWnop:
-		if v.Reg() != v.Args[0].Reg() {
-			v.Fatalf("input[0] and output not in same register %s", v.LongString())
-		}
 		// nothing to do
 	case ssa.OpLoadReg:
 		if v.Type.IsFlags() {
@@ -282,7 +279,7 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		p := s.Prog(v.Op.Asm())
 		p.From.Type = obj.TYPE_CONST
 		p.From.Offset = v.AuxInt >> 8
-		p.SetFrom3(obj.Addr{Type: obj.TYPE_CONST, Offset: v.AuxInt & 0xff})
+		p.SetFrom3Const(v.AuxInt & 0xff)
 		p.Reg = v.Args[0].Reg()
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = v.Reg()
@@ -302,7 +299,7 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 				p := s.Prog(arm.ABFC)
 				p.From.Type = obj.TYPE_CONST
 				p.From.Offset = int64(width)
-				p.SetFrom3(obj.Addr{Type: obj.TYPE_CONST, Offset: int64(lsb)})
+				p.SetFrom3Const(int64(lsb))
 				p.To.Type = obj.TYPE_REG
 				p.To.Reg = v.Reg()
 				break
@@ -657,6 +654,7 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		ssa.OpARMREV,
 		ssa.OpARMREV16,
 		ssa.OpARMRBIT,
+		ssa.OpARMSQRTF,
 		ssa.OpARMSQRTD,
 		ssa.OpARMNEGF,
 		ssa.OpARMNEGD,

src/cmd/compile/internal/arm64/ssa.go

@@ -100,9 +100,11 @@ func genIndexedOperand(v *ssa.Value) obj.Addr {
 	// Reg: base register, Index: (shifted) index register
 	mop := obj.Addr{Type: obj.TYPE_MEM, Reg: v.Args[0].Reg()}
 	switch v.Op {
-	case ssa.OpARM64MOVDloadidx8, ssa.OpARM64MOVDstoreidx8, ssa.OpARM64MOVDstorezeroidx8:
+	case ssa.OpARM64MOVDloadidx8, ssa.OpARM64MOVDstoreidx8, ssa.OpARM64MOVDstorezeroidx8,
+		ssa.OpARM64FMOVDloadidx8, ssa.OpARM64FMOVDstoreidx8:
 		mop.Index = arm64.REG_LSL | 3<<5 | v.Args[1].Reg()&31
-	case ssa.OpARM64MOVWloadidx4, ssa.OpARM64MOVWUloadidx4, ssa.OpARM64MOVWstoreidx4, ssa.OpARM64MOVWstorezeroidx4:
+	case ssa.OpARM64MOVWloadidx4, ssa.OpARM64MOVWUloadidx4, ssa.OpARM64MOVWstoreidx4, ssa.OpARM64MOVWstorezeroidx4,
+		ssa.OpARM64FMOVSloadidx4, ssa.OpARM64FMOVSstoreidx4:
 		mop.Index = arm64.REG_LSL | 2<<5 | v.Args[1].Reg()&31
 	case ssa.OpARM64MOVHloadidx2, ssa.OpARM64MOVHUloadidx2, ssa.OpARM64MOVHstoreidx2, ssa.OpARM64MOVHstorezeroidx2:
 		mop.Index = arm64.REG_LSL | 1<<5 | v.Args[1].Reg()&31
@@ -140,9 +142,6 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = y
 	case ssa.OpARM64MOVDnop:
-		if v.Reg() != v.Args[0].Reg() {
-			v.Fatalf("input[0] and output not in same register %s", v.LongString())
-		}
 		// nothing to do
 	case ssa.OpLoadReg:
 		if v.Type.IsFlags() {
@@ -230,7 +229,7 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		p.Reg = ra
 		p.From.Type = obj.TYPE_REG
 		p.From.Reg = rm
-		p.SetFrom3(obj.Addr{Type: obj.TYPE_REG, Reg: rn})
+		p.SetFrom3Reg(rn)
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = rt
 	case ssa.OpARM64ADDconst,
@@ -293,7 +292,7 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		p := s.Prog(v.Op.Asm())
 		p.From.Type = obj.TYPE_CONST
 		p.From.Offset = v.AuxInt
-		p.SetFrom3(obj.Addr{Type: obj.TYPE_REG, Reg: v.Args[0].Reg()})
+		p.SetFrom3Reg(v.Args[0].Reg())
 		p.Reg = v.Args[1].Reg()
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = v.Reg()
@@ -435,7 +434,9 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		ssa.OpARM64MOVHUloadidx2,
 		ssa.OpARM64MOVWloadidx4,
 		ssa.OpARM64MOVWUloadidx4,
-		ssa.OpARM64MOVDloadidx8:
+		ssa.OpARM64MOVDloadidx8,
+		ssa.OpARM64FMOVDloadidx8,
+		ssa.OpARM64FMOVSloadidx4:
 		p := s.Prog(v.Op.Asm())
 		p.From = genIndexedOperand(v)
 		p.To.Type = obj.TYPE_REG
@@ -472,7 +473,9 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		ssa.OpARM64FMOVDstoreidx,
 		ssa.OpARM64MOVHstoreidx2,
 		ssa.OpARM64MOVWstoreidx4,
-		ssa.OpARM64MOVDstoreidx8:
+		ssa.OpARM64FMOVSstoreidx4,
+		ssa.OpARM64MOVDstoreidx8,
+		ssa.OpARM64FMOVDstoreidx8:
 		p := s.Prog(v.Op.Asm())
 		p.To = genIndexedOperand(v)
 		p.From.Type = obj.TYPE_REG
@@ -516,17 +519,13 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		ssagen.AddAux(&p.To, v)
 	case ssa.OpARM64BFI,
 		ssa.OpARM64BFXIL:
-		r := v.Reg()
-		if r != v.Args[0].Reg() {
-			v.Fatalf("input[0] and output not in same register %s", v.LongString())
-		}
 		p := s.Prog(v.Op.Asm())
 		p.From.Type = obj.TYPE_CONST
 		p.From.Offset = v.AuxInt >> 8
-		p.SetFrom3(obj.Addr{Type: obj.TYPE_CONST, Offset: v.AuxInt & 0xff})
+		p.SetFrom3Const(v.AuxInt & 0xff)
 		p.Reg = v.Args[1].Reg()
 		p.To.Type = obj.TYPE_REG
-		p.To.Reg = r
+		p.To.Reg = v.Reg()
 	case ssa.OpARM64SBFIZ,
 		ssa.OpARM64SBFX,
 		ssa.OpARM64UBFIZ,
@@ -534,7 +533,7 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		p := s.Prog(v.Op.Asm())
 		p.From.Type = obj.TYPE_CONST
 		p.From.Offset = v.AuxInt >> 8
-		p.SetFrom3(obj.Addr{Type: obj.TYPE_CONST, Offset: v.AuxInt & 0xff})
+		p.SetFrom3Const(v.AuxInt & 0xff)
 		p.Reg = v.Args[0].Reg()
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = v.Reg()
@@ -894,6 +893,7 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		ssa.OpARM64FMOVSgpfp,
 		ssa.OpARM64FNEGS,
 		ssa.OpARM64FNEGD,
+		ssa.OpARM64FSQRTS,
 		ssa.OpARM64FSQRTD,
 		ssa.OpARM64FCVTZSSW,
 		ssa.OpARM64FCVTZSDW,
@@ -953,7 +953,7 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		p.From.Type = obj.TYPE_REG // assembler encodes conditional bits in Reg
 		p.From.Reg = condBits[ssa.Op(v.AuxInt)]
 		p.Reg = v.Args[0].Reg()
-		p.SetFrom3(obj.Addr{Type: obj.TYPE_REG, Reg: r1})
+		p.SetFrom3Reg(r1)
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = v.Reg()
 	case ssa.OpARM64DUFFZERO:

src/cmd/compile/internal/base/debug.go

@@ -29,28 +29,29 @@ var Debug = DebugFlags{
 // The -d option takes a comma-separated list of settings.
 // Each setting is name=value; for ints, name is short for name=1.
 type DebugFlags struct {
-	Append        int    `help:"print information about append compilation"`
-	Checkptr      int    `help:"instrument unsafe pointer conversions"`
-	Closure       int    `help:"print information about closure compilation"`
-	DclStack      int    `help:"run internal dclstack check"`
-	Defer         int    `help:"print information about defer compilation"`
-	DisableNil    int    `help:"disable nil checks"`
-	DumpPtrs      int    `help:"show Node pointers values in dump output"`
-	DwarfInl      int    `help:"print information about DWARF inlined function creation"`
-	Export        int    `help:"print export data"`
-	Fieldtrack    *int   `help:"enable field tracking"`
-	GCProg        int    `help:"print dump of GC programs"`
-	Libfuzzer     int    `help:"enable coverage instrumentation for libfuzzer"`
-	LocationLists int    `help:"print information about DWARF location list creation"`
-	Nil           int    `help:"print information about nil checks"`
-	PCTab         string `help:"print named pc-value table"`
-	Panic         int    `help:"show all compiler panics"`
-	Slice         int    `help:"print information about slice compilation"`
-	SoftFloat     int    `help:"force compiler to emit soft-float code"`
-	TypeAssert    int    `help:"print information about type assertion inlining"`
-	TypecheckInl  int    `help:"eager typechecking of inline function bodies"`
-	WB            int    `help:"print information about write barriers"`
-	ABIWrap       int    `help:"print information about ABI wrapper generation"`
+	Append               int    `help:"print information about append compilation"`
+	Checkptr             int    `help:"instrument unsafe pointer conversions"`
+	Closure              int    `help:"print information about closure compilation"`
+	DclStack             int    `help:"run internal dclstack check"`
+	Defer                int    `help:"print information about defer compilation"`
+	DisableNil           int    `help:"disable nil checks"`
+	DumpPtrs             int    `help:"show Node pointers values in dump output"`
+	DwarfInl             int    `help:"print information about DWARF inlined function creation"`
+	Export               int    `help:"print export data"`
+	Fieldtrack           *int   `help:"enable field tracking"`
+	GCProg               int    `help:"print dump of GC programs"`
+	InlFuncsWithClosures int    `help:"allow functions with closures to be inlined"`
+	Libfuzzer            int    `help:"enable coverage instrumentation for libfuzzer"`
+	LocationLists        int    `help:"print information about DWARF location list creation"`
+	Nil                  int    `help:"print information about nil checks"`
+	PCTab                string `help:"print named pc-value table"`
+	Panic                int    `help:"show all compiler panics"`
+	Slice                int    `help:"print information about slice compilation"`
+	SoftFloat            int    `help:"force compiler to emit soft-float code"`
+	TypeAssert           int    `help:"print information about type assertion inlining"`
+	TypecheckInl         int    `help:"eager typechecking of inline function bodies"`
+	WB                   int    `help:"print information about write barriers"`
+	ABIWrap              int    `help:"print information about ABI wrapper generation"`
 
 	any bool // set when any of the values have been set
 }

src/cmd/compile/internal/base/flag.go

@@ -54,6 +54,7 @@ type CmdFlags struct {
 	C CountFlag    "help:\"disable printing of columns in error messages\""
 	D string       "help:\"set relative `path` for local imports\""
 	E CountFlag    "help:\"debug symbol export\""
+	G CountFlag    "help:\"accept generic code\""
 	I func(string) "help:\"add `directory` to import search path\""
 	K CountFlag    "help:\"debug missing line numbers\""
 	L CountFlag    "help:\"show full file names in error messages\""
@@ -158,6 +159,7 @@ func ParseFlags() {
 	Flag.LinkShared = &Ctxt.Flag_linkshared
 	Flag.Shared = &Ctxt.Flag_shared
 	Flag.WB = true
+	Debug.InlFuncsWithClosures = 1
 
 	Flag.Cfg.ImportMap = make(map[string]string)
 

src/cmd/compile/internal/dwarfgen/dwarf.go

@@ -271,8 +271,7 @@ func createSimpleVar(fnsym *obj.LSym, n *ir.Name) *dwarf.Var {
 		if base.Ctxt.FixedFrameSize() == 0 {
 			offs -= int64(types.PtrSize)
 		}
-		if objabi.Framepointer_enabled || objabi.GOARCH == "arm64" {
-			// There is a word space for FP on ARM64 even if the frame pointer is disabled
+		if objabi.Framepointer_enabled {
 			offs -= int64(types.PtrSize)
 		}
 

src/cmd/compile/internal/dwarfgen/dwinl.go

@@ -247,7 +247,8 @@ func makePreinlineDclMap(fnsym *obj.LSym) map[varPos]int {
 			DeclCol:  pos.Col(),
 		}
 		if _, found := m[vp]; found {
-			base.Fatalf("child dcl collision on symbol %s within %v\n", n.Sym().Name, fnsym.Name)
+			// We can see collisions (variables with the same name/file/line/col) in obfuscated or machine-generated code -- see issue 44378 for an example. Skip duplicates in such cases, since it is unlikely that a human will be debugging such code.
+			continue
 		}
 		m[vp] = i
 	}

src/cmd/compile/internal/dwarfgen/scope.go

@@ -37,7 +37,9 @@ func assembleScopes(fnsym *obj.LSym, fn *ir.Func, dwarfVars []*dwarf.Var, varSco
 	}
 
 	scopeVariables(dwarfVars, varScopes, dwarfScopes)
-	scopePCs(fnsym, fn.Marks, dwarfScopes)
+	if fnsym.Func().Text != nil {
+		scopePCs(fnsym, fn.Marks, dwarfScopes)
+	}
 	return compactScopes(dwarfScopes)
 }
 

src/cmd/compile/internal/escape/escape.go

@@ -1625,9 +1625,10 @@ func containsClosure(f, c *ir.Func) bool {
 
 // leak records that parameter l leaks to sink.
 func (l *location) leakTo(sink *location, derefs int) {
-	// If sink is a result parameter and we can fit return bits
-	// into the escape analysis tag, then record a return leak.
-	if sink.isName(ir.PPARAMOUT) && sink.curfn == l.curfn {
+	// If sink is a result parameter that doesn't escape (#44614)
+	// and we can fit return bits into the escape analysis tag,
+	// then record as a result leak.
+	if !sink.escapes && sink.isName(ir.PPARAMOUT) && sink.curfn == l.curfn {
 		ri := sink.resultIndex - 1
 		if ri < numEscResults {
 			// Leak to result parameter.

src/cmd/compile/internal/gc/bootstrap.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build !go1.8
 // +build !go1.8
 
 package gc

src/cmd/compile/internal/gc/compile.go

@@ -43,6 +43,9 @@ func enqueueFunc(fn *ir.Func) {
 	if len(fn.Body) == 0 {
 		// Initialize ABI wrappers if necessary.
 		ssagen.InitLSym(fn, false)
+		types.CalcSize(fn.Type()) // TODO register args; remove this once all is done by abiutils
+		a := ssagen.AbiForFunc(fn)
+		a.ABIAnalyze(fn.Type()) // will set parameter spill/home locations correctly
 		liveness.WriteFuncMap(fn)
 		return
 	}

src/cmd/compile/internal/gc/export.go

@@ -25,6 +25,11 @@ func exportf(bout *bio.Writer, format string, args ...interface{}) {
 func dumpexport(bout *bio.Writer) {
 	p := &exporter{marked: make(map[*types.Type]bool)}
 	for _, n := range typecheck.Target.Exports {
+		// Must catch it here rather than Export(), because the type can be
+		// not fully set (still TFORW) when Export() is called.
+		if n.Type() != nil && n.Type().HasTParam() {
+			base.Fatalf("Cannot (yet) export a generic type: %v", n)
+		}
 		p.markObject(n)
 	}
 

src/cmd/compile/internal/gc/pprof.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build go1.8
 // +build go1.8
 
 package gc

src/cmd/compile/internal/gc/trace.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build go1.7
 // +build go1.7
 
 package gc

src/cmd/compile/internal/importer/exportdata.go

@@ -0,0 +1,92 @@
+// UNREVIEWED
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements FindExportData.
+
+package importer
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"strconv"
+	"strings"
+)
+
+func readGopackHeader(r *bufio.Reader) (name string, size int, err error) {
+	// See $GOROOT/include/ar.h.
+	hdr := make([]byte, 16+12+6+6+8+10+2)
+	_, err = io.ReadFull(r, hdr)
+	if err != nil {
+		return
+	}
+	// leave for debugging
+	if false {
+		fmt.Printf("header: %s", hdr)
+	}
+	s := strings.TrimSpace(string(hdr[16+12+6+6+8:][:10]))
+	size, err = strconv.Atoi(s)
+	if err != nil || hdr[len(hdr)-2] != '`' || hdr[len(hdr)-1] != '\n' {
+		err = fmt.Errorf("invalid archive header")
+		return
+	}
+	name = strings.TrimSpace(string(hdr[:16]))
+	return
+}
+
+// FindExportData positions the reader r at the beginning of the
+// export data section of an underlying GC-created object/archive
+// file by reading from it. The reader must be positioned at the
+// start of the file before calling this function. The hdr result
+// is the string before the export data, either "$$" or "$$B".
+//
+func FindExportData(r *bufio.Reader) (hdr string, err error) {
+	// Read first line to make sure this is an object file.
+	line, err := r.ReadSlice('\n')
+	if err != nil {
+		err = fmt.Errorf("can't find export data (%v)", err)
+		return
+	}
+
+	if string(line) == "!<arch>\n" {
+		// Archive file. Scan to __.PKGDEF.
+		var name string
+		if name, _, err = readGopackHeader(r); err != nil {
+			return
+		}
+
+		// First entry should be __.PKGDEF.
+		if name != "__.PKGDEF" {
+			err = fmt.Errorf("go archive is missing __.PKGDEF")
+			return
+		}
+
+		// Read first line of __.PKGDEF data, so that line
+		// is once again the first line of the input.
+		if line, err = r.ReadSlice('\n'); err != nil {
+			err = fmt.Errorf("can't find export data (%v)", err)
+			return
+		}
+	}
+
+	// Now at __.PKGDEF in archive or still at beginning of file.
+	// Either way, line should begin with "go object ".
+	if !strings.HasPrefix(string(line), "go object ") {
+		err = fmt.Errorf("not a Go object file")
+		return
+	}
+
+	// Skip over object header to export data.
+	// Begins after first line starting with $$.
+	for line[0] != '$' {
+		if line, err = r.ReadSlice('\n'); err != nil {
+			err = fmt.Errorf("can't find export data (%v)", err)
+			return
+		}
+	}
+	hdr = string(line)
+
+	return
+}

src/cmd/compile/internal/importer/gcimporter.go

@@ -0,0 +1,175 @@
+// UNREVIEWED
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// package importer implements Import for gc-generated object files.
+package importer
+
+import (
+	"bufio"
+	"cmd/compile/internal/types2"
+	"fmt"
+	"go/build"
+	"io"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// debugging/development support
+const debug = false
+
+var pkgExts = [...]string{".a", ".o"}
+
+// FindPkg returns the filename and unique package id for an import
+// path based on package information provided by build.Import (using
+// the build.Default build.Context). A relative srcDir is interpreted
+// relative to the current working directory.
+// If no file was found, an empty filename is returned.
+//
+func FindPkg(path, srcDir string) (filename, id string) {
+	if path == "" {
+		return
+	}
+
+	var noext string
+	switch {
+	default:
+		// "x" -> "$GOPATH/pkg/$GOOS_$GOARCH/x.ext", "x"
+		// Don't require the source files to be present.
+		if abs, err := filepath.Abs(srcDir); err == nil { // see issue 14282
+			srcDir = abs
+		}
+		bp, _ := build.Import(path, srcDir, build.FindOnly|build.AllowBinary)
+		if bp.PkgObj == "" {
+			id = path // make sure we have an id to print in error message
+			return
+		}
+		noext = strings.TrimSuffix(bp.PkgObj, ".a")
+		id = bp.ImportPath
+
+	case build.IsLocalImport(path):
+		// "./x" -> "/this/directory/x.ext", "/this/directory/x"
+		noext = filepath.Join(srcDir, path)
+		id = noext
+
+	case filepath.IsAbs(path):
+		// for completeness only - go/build.Import
+		// does not support absolute imports
+		// "/x" -> "/x.ext", "/x"
+		noext = path
+		id = path
+	}
+
+	if false { // for debugging
+		if path != id {
+			fmt.Printf("%s -> %s\n", path, id)
+		}
+	}
+
+	// try extensions
+	for _, ext := range pkgExts {
+		filename = noext + ext
+		if f, err := os.Stat(filename); err == nil && !f.IsDir() {
+			return
+		}
+	}
+
+	filename = "" // not found
+	return
+}
+
+// Import imports a gc-generated package given its import path and srcDir, adds
+// the corresponding package object to the packages map, and returns the object.
+// The packages map must contain all packages already imported.
+//
+func Import(packages map[string]*types2.Package, path, srcDir string, lookup func(path string) (io.ReadCloser, error)) (pkg *types2.Package, err error) {
+	var rc io.ReadCloser
+	var id string
+	if lookup != nil {
+		// With custom lookup specified, assume that caller has
+		// converted path to a canonical import path for use in the map.
+		if path == "unsafe" {
+			return types2.Unsafe, nil
+		}
+		id = path
+
+		// No need to re-import if the package was imported completely before.
+		if pkg = packages[id]; pkg != nil && pkg.Complete() {
+			return
+		}
+		f, err := lookup(path)
+		if err != nil {
+			return nil, err
+		}
+		rc = f
+	} else {
+		var filename string
+		filename, id = FindPkg(path, srcDir)
+		if filename == "" {
+			if path == "unsafe" {
+				return types2.Unsafe, nil
+			}
+			return nil, fmt.Errorf("can't find import: %q", id)
+		}
+
+		// no need to re-import if the package was imported completely before
+		if pkg = packages[id]; pkg != nil && pkg.Complete() {
+			return
+		}
+
+		// open file
+		f, err := os.Open(filename)
+		if err != nil {
+			return nil, err
+		}
+		defer func() {
+			if err != nil {
+				// add file name to error
+				err = fmt.Errorf("%s: %v", filename, err)
+			}
+		}()
+		rc = f
+	}
+	defer rc.Close()
+
+	var hdr string
+	buf := bufio.NewReader(rc)
+	if hdr, err = FindExportData(buf); err != nil {
+		return
+	}
+
+	switch hdr {
+	case "$$\n":
+		err = fmt.Errorf("import %q: old textual export format no longer supported (recompile library)", path)
+
+	case "$$B\n":
+		var data []byte
+		data, err = ioutil.ReadAll(buf)
+		if err != nil {
+			break
+		}
+
+		// The indexed export format starts with an 'i'; the older
+		// binary export format starts with a 'c', 'd', or 'v'
+		// (from "version"). Select appropriate importer.
+		if len(data) > 0 && data[0] == 'i' {
+			_, pkg, err = iImportData(packages, data[1:], id)
+		} else {
+			err = fmt.Errorf("import %q: old binary export format no longer supported (recompile library)", path)
+		}
+
+	default:
+		err = fmt.Errorf("import %q: unknown export data header: %q", path, hdr)
+	}
+
+	return
+}
+
+type byPath []*types2.Package
+
+func (a byPath) Len() int           { return len(a) }
+func (a byPath) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
+func (a byPath) Less(i, j int) bool { return a[i].Path() < a[j].Path() }

src/cmd/compile/internal/importer/gcimporter_test.go

@@ -0,0 +1,611 @@
+// UNREVIEWED
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package importer
+
+import (
+	"bytes"
+	"cmd/compile/internal/types2"
+	"fmt"
+	"internal/testenv"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"testing"
+	"time"
+)
+
+// skipSpecialPlatforms causes the test to be skipped for platforms where
+// builders (build.golang.org) don't have access to compiled packages for
+// import.
+func skipSpecialPlatforms(t *testing.T) {
+	switch platform := runtime.GOOS + "-" + runtime.GOARCH; platform {
+	case "darwin-arm64":
+		t.Skipf("no compiled packages available for import on %s", platform)
+	}
+}
+
+// compile runs the compiler on filename, with dirname as the working directory,
+// and writes the output file to outdirname.
+func compile(t *testing.T, dirname, filename, outdirname string) string {
+	// filename must end with ".go"
+	if !strings.HasSuffix(filename, ".go") {
+		t.Fatalf("filename doesn't end in .go: %s", filename)
+	}
+	basename := filepath.Base(filename)
+	outname := filepath.Join(outdirname, basename[:len(basename)-2]+"o")
+	cmd := exec.Command(testenv.GoToolPath(t), "tool", "compile", "-o", outname, filename)
+	cmd.Dir = dirname
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Logf("%s", out)
+		t.Fatalf("go tool compile %s failed: %s", filename, err)
+	}
+	return outname
+}
+
+func testPath(t *testing.T, path, srcDir string) *types2.Package {
+	t0 := time.Now()
+	pkg, err := Import(make(map[string]*types2.Package), path, srcDir, nil)
+	if err != nil {
+		t.Errorf("testPath(%s): %s", path, err)
+		return nil
+	}
+	t.Logf("testPath(%s): %v", path, time.Since(t0))
+	return pkg
+}
+
+const maxTime = 30 * time.Second
+
+func testDir(t *testing.T, dir string, endTime time.Time) (nimports int) {
+	dirname := filepath.Join(runtime.GOROOT(), "pkg", runtime.GOOS+"_"+runtime.GOARCH, dir)
+	list, err := ioutil.ReadDir(dirname)
+	if err != nil {
+		t.Fatalf("testDir(%s): %s", dirname, err)
+	}
+	for _, f := range list {
+		if time.Now().After(endTime) {
+			t.Log("testing time used up")
+			return
+		}
+		switch {
+		case !f.IsDir():
+			// try extensions
+			for _, ext := range pkgExts {
+				if strings.HasSuffix(f.Name(), ext) {
+					name := f.Name()[0 : len(f.Name())-len(ext)] // remove extension
+					if testPath(t, filepath.Join(dir, name), dir) != nil {
+						nimports++
+					}
+				}
+			}
+		case f.IsDir():
+			nimports += testDir(t, filepath.Join(dir, f.Name()), endTime)
+		}
+	}
+	return
+}
+
+func mktmpdir(t *testing.T) string {
+	tmpdir, err := ioutil.TempDir("", "gcimporter_test")
+	if err != nil {
+		t.Fatal("mktmpdir:", err)
+	}
+	if err := os.Mkdir(filepath.Join(tmpdir, "testdata"), 0700); err != nil {
+		os.RemoveAll(tmpdir)
+		t.Fatal("mktmpdir:", err)
+	}
+	return tmpdir
+}
+
+func TestImportTestdata(t *testing.T) {
+	// This package only handles gc export data.
+	if runtime.Compiler != "gc" {
+		t.Skipf("gc-built packages not available (compiler = %s)", runtime.Compiler)
+	}
+
+	tmpdir := mktmpdir(t)
+	defer os.RemoveAll(tmpdir)
+
+	compile(t, "testdata", "exports.go", filepath.Join(tmpdir, "testdata"))
+
+	if pkg := testPath(t, "./testdata/exports", tmpdir); pkg != nil {
+		// The package's Imports list must include all packages
+		// explicitly imported by exports.go, plus all packages
+		// referenced indirectly via exported objects in exports.go.
+		// With the textual export format, the list may also include
+		// additional packages that are not strictly required for
+		// import processing alone (they are exported to err "on
+		// the safe side").
+		// TODO(gri) update the want list to be precise, now that
+		// the textual export data is gone.
+		got := fmt.Sprint(pkg.Imports())
+		for _, want := range []string{"go/ast", "go/token"} {
+			if !strings.Contains(got, want) {
+				t.Errorf(`Package("exports").Imports() = %s, does not contain %s`, got, want)
+			}
+		}
+	}
+}
+
+func TestVersionHandling(t *testing.T) {
+	skipSpecialPlatforms(t)
+
+	// This package only handles gc export data.
+	if runtime.Compiler != "gc" {
+		t.Skipf("gc-built packages not available (compiler = %s)", runtime.Compiler)
+	}
+
+	const dir = "./testdata/versions"
+	list, err := ioutil.ReadDir(dir)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	tmpdir := mktmpdir(t)
+	defer os.RemoveAll(tmpdir)
+	corruptdir := filepath.Join(tmpdir, "testdata", "versions")
+	if err := os.Mkdir(corruptdir, 0700); err != nil {
+		t.Fatal(err)
+	}
+
+	for _, f := range list {
+		name := f.Name()
+		if !strings.HasSuffix(name, ".a") {
+			continue // not a package file
+		}
+		if strings.Contains(name, "corrupted") {
+			continue // don't process a leftover corrupted file
+		}
+		pkgpath := "./" + name[:len(name)-2]
+
+		if testing.Verbose() {
+			t.Logf("importing %s", name)
+		}
+
+		// test that export data can be imported
+		_, err := Import(make(map[string]*types2.Package), pkgpath, dir, nil)
+		if err != nil {
+			// ok to fail if it fails with a no longer supported error for select files
+			if strings.Contains(err.Error(), "no longer supported") {
+				switch name {
+				case "test_go1.7_0.a", "test_go1.7_1.a",
+					"test_go1.8_4.a", "test_go1.8_5.a",
+					"test_go1.11_6b.a", "test_go1.11_999b.a":
+					continue
+				}
+				// fall through
+			}
+			// ok to fail if it fails with a newer version error for select files
+			if strings.Contains(err.Error(), "newer version") {
+				switch name {
+				case "test_go1.11_999i.a":
+					continue
+				}
+				// fall through
+			}
+			t.Errorf("import %q failed: %v", pkgpath, err)
+			continue
+		}
+
+		// create file with corrupted export data
+		// 1) read file
+		data, err := ioutil.ReadFile(filepath.Join(dir, name))
+		if err != nil {
+			t.Fatal(err)
+		}
+		// 2) find export data
+		i := bytes.Index(data, []byte("\n$$B\n")) + 5
+		j := bytes.Index(data[i:], []byte("\n$$\n")) + i
+		if i < 0 || j < 0 || i > j {
+			t.Fatalf("export data section not found (i = %d, j = %d)", i, j)
+		}
+		// 3) corrupt the data (increment every 7th byte)
+		for k := j - 13; k >= i; k -= 7 {
+			data[k]++
+		}
+		// 4) write the file
+		pkgpath += "_corrupted"
+		filename := filepath.Join(corruptdir, pkgpath) + ".a"
+		ioutil.WriteFile(filename, data, 0666)
+
+		// test that importing the corrupted file results in an error
+		_, err = Import(make(map[string]*types2.Package), pkgpath, corruptdir, nil)
+		if err == nil {
+			t.Errorf("import corrupted %q succeeded", pkgpath)
+		} else if msg := err.Error(); !strings.Contains(msg, "version skew") {
+			t.Errorf("import %q error incorrect (%s)", pkgpath, msg)
+		}
+	}
+}
+
+func TestImportStdLib(t *testing.T) {
+	skipSpecialPlatforms(t)
+
+	// This package only handles gc export data.
+	if runtime.Compiler != "gc" {
+		t.Skipf("gc-built packages not available (compiler = %s)", runtime.Compiler)
+	}
+
+	dt := maxTime
+	if testing.Short() && testenv.Builder() == "" {
+		dt = 10 * time.Millisecond
+	}
+	nimports := testDir(t, "", time.Now().Add(dt)) // installed packages
+	t.Logf("tested %d imports", nimports)
+}
+
+var importedObjectTests = []struct {
+	name string
+	want string
+}{
+	// non-interfaces
+	{"crypto.Hash", "type Hash uint"},
+	{"go/ast.ObjKind", "type ObjKind int"},
+	{"go/types.Qualifier", "type Qualifier func(*Package) string"},
+	{"go/types.Comparable", "func Comparable(T Type) bool"},
+	{"math.Pi", "const Pi untyped float"},
+	{"math.Sin", "func Sin(x float64) float64"},
+	{"go/ast.NotNilFilter", "func NotNilFilter(_ string, v reflect.Value) bool"},
+	{"go/internal/gcimporter.FindPkg", "func FindPkg(path string, srcDir string) (filename string, id string)"},
+
+	// interfaces
+	{"context.Context", "type Context interface{Deadline() (deadline time.Time, ok bool); Done() <-chan struct{}; Err() error; Value(key interface{}) interface{}}"},
+	{"crypto.Decrypter", "type Decrypter interface{Decrypt(rand io.Reader, msg []byte, opts DecrypterOpts) (plaintext []byte, err error); Public() PublicKey}"},
+	{"encoding.BinaryMarshaler", "type BinaryMarshaler interface{MarshalBinary() (data []byte, err error)}"},
+	{"io.Reader", "type Reader interface{Read(p []byte) (n int, err error)}"},
+	{"io.ReadWriter", "type ReadWriter interface{Reader; Writer}"},
+	{"go/ast.Node", "type Node interface{End() go/token.Pos; Pos() go/token.Pos}"},
+	// go/types.Type has grown much larger - excluded for now
+	// {"go/types.Type", "type Type interface{String() string; Underlying() Type}"},
+}
+
+func TestImportedTypes(t *testing.T) {
+	skipSpecialPlatforms(t)
+
+	// This package only handles gc export data.
+	if runtime.Compiler != "gc" {
+		t.Skipf("gc-built packages not available (compiler = %s)", runtime.Compiler)
+	}
+
+	for _, test := range importedObjectTests {
+		s := strings.Split(test.name, ".")
+		if len(s) != 2 {
+			t.Fatal("inconsistent test data")
+		}
+		importPath := s[0]
+		objName := s[1]
+
+		pkg, err := Import(make(map[string]*types2.Package), importPath, ".", nil)
+		if err != nil {
+			t.Error(err)
+			continue
+		}
+
+		obj := pkg.Scope().Lookup(objName)
+		if obj == nil {
+			t.Errorf("%s: object not found", test.name)
+			continue
+		}
+
+		got := types2.ObjectString(obj, types2.RelativeTo(pkg))
+		if got != test.want {
+			t.Errorf("%s: got %q; want %q", test.name, got, test.want)
+		}
+
+		if named, _ := obj.Type().(*types2.Named); named != nil {
+			verifyInterfaceMethodRecvs(t, named, 0)
+		}
+	}
+}
+
+// verifyInterfaceMethodRecvs verifies that method receiver types
+// are named if the methods belong to a named interface type.
+func verifyInterfaceMethodRecvs(t *testing.T, named *types2.Named, level int) {
+	// avoid endless recursion in case of an embedding bug that lead to a cycle
+	if level > 10 {
+		t.Errorf("%s: embeds itself", named)
+		return
+	}
+
+	iface, _ := named.Underlying().(*types2.Interface)
+	if iface == nil {
+		return // not an interface
+	}
+
+	// check explicitly declared methods
+	for i := 0; i < iface.NumExplicitMethods(); i++ {
+		m := iface.ExplicitMethod(i)
+		recv := m.Type().(*types2.Signature).Recv()
+		if recv == nil {
+			t.Errorf("%s: missing receiver type", m)
+			continue
+		}
+		if recv.Type() != named {
+			t.Errorf("%s: got recv type %s; want %s", m, recv.Type(), named)
+		}
+	}
+
+	// check embedded interfaces (if they are named, too)
+	for i := 0; i < iface.NumEmbeddeds(); i++ {
+		// embedding of interfaces cannot have cycles; recursion will terminate
+		if etype, _ := iface.EmbeddedType(i).(*types2.Named); etype != nil {
+			verifyInterfaceMethodRecvs(t, etype, level+1)
+		}
+	}
+}
+
+func TestIssue5815(t *testing.T) {
+	skipSpecialPlatforms(t)
+
+	// This package only handles gc export data.
+	if runtime.Compiler != "gc" {
+		t.Skipf("gc-built packages not available (compiler = %s)", runtime.Compiler)
+	}
+
+	pkg := importPkg(t, "strings", ".")
+
+	scope := pkg.Scope()
+	for _, name := range scope.Names() {
+		obj := scope.Lookup(name)
+		if obj.Pkg() == nil {
+			t.Errorf("no pkg for %s", obj)
+		}
+		if tname, _ := obj.(*types2.TypeName); tname != nil {
+			named := tname.Type().(*types2.Named)
+			for i := 0; i < named.NumMethods(); i++ {
+				m := named.Method(i)
+				if m.Pkg() == nil {
+					t.Errorf("no pkg for %s", m)
+				}
+			}
+		}
+	}
+}
+
+// Smoke test to ensure that imported methods get the correct package.
+func TestCorrectMethodPackage(t *testing.T) {
+	skipSpecialPlatforms(t)
+
+	// This package only handles gc export data.
+	if runtime.Compiler != "gc" {
+		t.Skipf("gc-built packages not available (compiler = %s)", runtime.Compiler)
+	}
+
+	imports := make(map[string]*types2.Package)
+	_, err := Import(imports, "net/http", ".", nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	mutex := imports["sync"].Scope().Lookup("Mutex").(*types2.TypeName).Type()
+	obj, _, _ := types2.LookupFieldOrMethod(types2.NewPointer(mutex), false, nil, "Lock")
+	lock := obj.(*types2.Func)
+	if got, want := lock.Pkg().Path(), "sync"; got != want {
+		t.Errorf("got package path %q; want %q", got, want)
+	}
+}
+
+func TestIssue13566(t *testing.T) {
+	skipSpecialPlatforms(t)
+
+	// This package only handles gc export data.
+	if runtime.Compiler != "gc" {
+		t.Skipf("gc-built packages not available (compiler = %s)", runtime.Compiler)
+	}
+
+	// On windows, we have to set the -D option for the compiler to avoid having a drive
+	// letter and an illegal ':' in the import path - just skip it (see also issue #3483).
+	if runtime.GOOS == "windows" {
+		t.Skip("avoid dealing with relative paths/drive letters on windows")
+	}
+
+	tmpdir := mktmpdir(t)
+	defer os.RemoveAll(tmpdir)
+	testoutdir := filepath.Join(tmpdir, "testdata")
+
+	// b.go needs to be compiled from the output directory so that the compiler can
+	// find the compiled package a. We pass the full path to compile() so that we
+	// don't have to copy the file to that directory.
+	bpath, err := filepath.Abs(filepath.Join("testdata", "b.go"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	compile(t, "testdata", "a.go", testoutdir)
+	compile(t, testoutdir, bpath, testoutdir)
+
+	// import must succeed (test for issue at hand)
+	pkg := importPkg(t, "./testdata/b", tmpdir)
+
+	// make sure all indirectly imported packages have names
+	for _, imp := range pkg.Imports() {
+		if imp.Name() == "" {
+			t.Errorf("no name for %s package", imp.Path())
+		}
+	}
+}
+
+func TestIssue13898(t *testing.T) {
+	skipSpecialPlatforms(t)
+
+	// This package only handles gc export data.
+	if runtime.Compiler != "gc" {
+		t.Skipf("gc-built packages not available (compiler = %s)", runtime.Compiler)
+	}
+
+	// import go/internal/gcimporter which imports go/types partially
+	imports := make(map[string]*types2.Package)
+	_, err := Import(imports, "go/internal/gcimporter", ".", nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// look for go/types package
+	var goTypesPkg *types2.Package
+	for path, pkg := range imports {
+		if path == "go/types" {
+			goTypesPkg = pkg
+			break
+		}
+	}
+	if goTypesPkg == nil {
+		t.Fatal("go/types not found")
+	}
+
+	// look for go/types2.Object type
+	obj := lookupObj(t, goTypesPkg.Scope(), "Object")
+	typ, ok := obj.Type().(*types2.Named)
+	if !ok {
+		t.Fatalf("go/types2.Object type is %v; wanted named type", typ)
+	}
+
+	// lookup go/types2.Object.Pkg method
+	m, index, indirect := types2.LookupFieldOrMethod(typ, false, nil, "Pkg")
+	if m == nil {
+		t.Fatalf("go/types2.Object.Pkg not found (index = %v, indirect = %v)", index, indirect)
+	}
+
+	// the method must belong to go/types
+	if m.Pkg().Path() != "go/types" {
+		t.Fatalf("found %v; want go/types", m.Pkg())
+	}
+}
+
+func TestIssue15517(t *testing.T) {
+	skipSpecialPlatforms(t)
+
+	// This package only handles gc export data.
+	if runtime.Compiler != "gc" {
+		t.Skipf("gc-built packages not available (compiler = %s)", runtime.Compiler)
+	}
+
+	// On windows, we have to set the -D option for the compiler to avoid having a drive
+	// letter and an illegal ':' in the import path - just skip it (see also issue #3483).
+	if runtime.GOOS == "windows" {
+		t.Skip("avoid dealing with relative paths/drive letters on windows")
+	}
+
+	tmpdir := mktmpdir(t)
+	defer os.RemoveAll(tmpdir)
+
+	compile(t, "testdata", "p.go", filepath.Join(tmpdir, "testdata"))
+
+	// Multiple imports of p must succeed without redeclaration errors.
+	// We use an import path that's not cleaned up so that the eventual
+	// file path for the package is different from the package path; this
+	// will expose the error if it is present.
+	//
+	// (Issue: Both the textual and the binary importer used the file path
+	// of the package to be imported as key into the shared packages map.
+	// However, the binary importer then used the package path to identify
+	// the imported package to mark it as complete; effectively marking the
+	// wrong package as complete. By using an "unclean" package path, the
+	// file and package path are different, exposing the problem if present.
+	// The same issue occurs with vendoring.)
+	imports := make(map[string]*types2.Package)
+	for i := 0; i < 3; i++ {
+		if _, err := Import(imports, "./././testdata/p", tmpdir, nil); err != nil {
+			t.Fatal(err)
+		}
+	}
+}
+
+func TestIssue15920(t *testing.T) {
+	skipSpecialPlatforms(t)
+
+	// This package only handles gc export data.
+	if runtime.Compiler != "gc" {
+		t.Skipf("gc-built packages not available (compiler = %s)", runtime.Compiler)
+	}
+
+	// On windows, we have to set the -D option for the compiler to avoid having a drive
+	// letter and an illegal ':' in the import path - just skip it (see also issue #3483).
+	if runtime.GOOS == "windows" {
+		t.Skip("avoid dealing with relative paths/drive letters on windows")
+	}
+
+	compileAndImportPkg(t, "issue15920")
+}
+
+func TestIssue20046(t *testing.T) {
+	skipSpecialPlatforms(t)
+
+	// This package only handles gc export data.
+	if runtime.Compiler != "gc" {
+		t.Skipf("gc-built packages not available (compiler = %s)", runtime.Compiler)
+	}
+
+	// On windows, we have to set the -D option for the compiler to avoid having a drive
+	// letter and an illegal ':' in the import path - just skip it (see also issue #3483).
+	if runtime.GOOS == "windows" {
+		t.Skip("avoid dealing with relative paths/drive letters on windows")
+	}
+
+	// "./issue20046".V.M must exist
+	pkg := compileAndImportPkg(t, "issue20046")
+	obj := lookupObj(t, pkg.Scope(), "V")
+	if m, index, indirect := types2.LookupFieldOrMethod(obj.Type(), false, nil, "M"); m == nil {
+		t.Fatalf("V.M not found (index = %v, indirect = %v)", index, indirect)
+	}
+}
+func TestIssue25301(t *testing.T) {
+	skipSpecialPlatforms(t)
+
+	// This package only handles gc export data.
+	if runtime.Compiler != "gc" {
+		t.Skipf("gc-built packages not available (compiler = %s)", runtime.Compiler)
+	}
+
+	// On windows, we have to set the -D option for the compiler to avoid having a drive
+	// letter and an illegal ':' in the import path - just skip it (see also issue #3483).
+	if runtime.GOOS == "windows" {
+		t.Skip("avoid dealing with relative paths/drive letters on windows")
+	}
+
+	compileAndImportPkg(t, "issue25301")
+}
+
+func TestIssue25596(t *testing.T) {
+	skipSpecialPlatforms(t)
+
+	// This package only handles gc export data.
+	if runtime.Compiler != "gc" {
+		t.Skipf("gc-built packages not available (compiler = %s)", runtime.Compiler)
+	}
+
+	// On windows, we have to set the -D option for the compiler to avoid having a drive
+	// letter and an illegal ':' in the import path - just skip it (see also issue #3483).
+	if runtime.GOOS == "windows" {
+		t.Skip("avoid dealing with relative paths/drive letters on windows")
+	}
+
+	compileAndImportPkg(t, "issue25596")
+}
+
+func importPkg(t *testing.T, path, srcDir string) *types2.Package {
+	pkg, err := Import(make(map[string]*types2.Package), path, srcDir, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return pkg
+}
+
+func compileAndImportPkg(t *testing.T, name string) *types2.Package {
+	tmpdir := mktmpdir(t)
+	defer os.RemoveAll(tmpdir)
+	compile(t, "testdata", name+".go", filepath.Join(tmpdir, "testdata"))
+	return importPkg(t, "./testdata/"+name, tmpdir)
+}
+
+func lookupObj(t *testing.T, scope *types2.Scope, name string) types2.Object {
+	if obj := scope.Lookup(name); obj != nil {
+		return obj
+	}
+	t.Fatalf("%s not found", name)
+	return nil
+}

src/cmd/compile/internal/importer/iimport.go

@@ -0,0 +1,612 @@
+// UNREVIEWED
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Indexed package import.
+// See cmd/compile/internal/gc/iexport.go for the export data format.
+
+package importer
+
+import (
+	"bytes"
+	"cmd/compile/internal/syntax"
+	"cmd/compile/internal/types2"
+	"encoding/binary"
+	"fmt"
+	"go/constant"
+	"go/token"
+	"io"
+	"math/big"
+	"sort"
+)
+
+type intReader struct {
+	*bytes.Reader
+	path string
+}
+
+func (r *intReader) int64() int64 {
+	i, err := binary.ReadVarint(r.Reader)
+	if err != nil {
+		errorf("import %q: read varint error: %v", r.path, err)
+	}
+	return i
+}
+
+func (r *intReader) uint64() uint64 {
+	i, err := binary.ReadUvarint(r.Reader)
+	if err != nil {
+		errorf("import %q: read varint error: %v", r.path, err)
+	}
+	return i
+}
+
+const predeclReserved = 32
+
+type itag uint64
+
+const (
+	// Types
+	definedType itag = iota
+	pointerType
+	sliceType
+	arrayType
+	chanType
+	mapType
+	signatureType
+	structType
+	interfaceType
+)
+
+const io_SeekCurrent = 1 // io.SeekCurrent (not defined in Go 1.4)
+
+// iImportData imports a package from the serialized package data
+// and returns the number of bytes consumed and a reference to the package.
+// If the export data version is not recognized or the format is otherwise
+// compromised, an error is returned.
+func iImportData(imports map[string]*types2.Package, data []byte, path string) (_ int, pkg *types2.Package, err error) {
+	const currentVersion = 1
+	version := int64(-1)
+	defer func() {
+		if e := recover(); e != nil {
+			if version > currentVersion {
+				err = fmt.Errorf("cannot import %q (%v), export data is newer version - update tool", path, e)
+			} else {
+				err = fmt.Errorf("cannot import %q (%v), possibly version skew - reinstall package", path, e)
+			}
+		}
+	}()
+
+	r := &intReader{bytes.NewReader(data), path}
+
+	version = int64(r.uint64())
+	switch version {
+	case currentVersion, 0:
+	default:
+		errorf("unknown iexport format version %d", version)
+	}
+
+	sLen := int64(r.uint64())
+	dLen := int64(r.uint64())
+
+	whence, _ := r.Seek(0, io_SeekCurrent)
+	stringData := data[whence : whence+sLen]
+	declData := data[whence+sLen : whence+sLen+dLen]
+	r.Seek(sLen+dLen, io_SeekCurrent)
+
+	p := iimporter{
+		ipath:   path,
+		version: int(version),
+
+		stringData:  stringData,
+		stringCache: make(map[uint64]string),
+		pkgCache:    make(map[uint64]*types2.Package),
+
+		declData: declData,
+		pkgIndex: make(map[*types2.Package]map[string]uint64),
+		typCache: make(map[uint64]types2.Type),
+	}
+
+	for i, pt := range predeclared {
+		p.typCache[uint64(i)] = pt
+	}
+
+	pkgList := make([]*types2.Package, r.uint64())
+	for i := range pkgList {
+		pkgPathOff := r.uint64()
+		pkgPath := p.stringAt(pkgPathOff)
+		pkgName := p.stringAt(r.uint64())
+		_ = r.uint64() // package height; unused by go/types
+
+		if pkgPath == "" {
+			pkgPath = path
+		}
+		pkg := imports[pkgPath]
+		if pkg == nil {
+			pkg = types2.NewPackage(pkgPath, pkgName)
+			imports[pkgPath] = pkg
+		} else if pkg.Name() != pkgName {
+			errorf("conflicting names %s and %s for package %q", pkg.Name(), pkgName, path)
+		}
+
+		p.pkgCache[pkgPathOff] = pkg
+
+		nameIndex := make(map[string]uint64)
+		for nSyms := r.uint64(); nSyms > 0; nSyms-- {
+			name := p.stringAt(r.uint64())
+			nameIndex[name] = r.uint64()
+		}
+
+		p.pkgIndex[pkg] = nameIndex
+		pkgList[i] = pkg
+	}
+
+	localpkg := pkgList[0]
+
+	names := make([]string, 0, len(p.pkgIndex[localpkg]))
+	for name := range p.pkgIndex[localpkg] {
+		names = append(names, name)
+	}
+	sort.Strings(names)
+	for _, name := range names {
+		p.doDecl(localpkg, name)
+	}
+
+	for _, typ := range p.interfaceList {
+		typ.Complete()
+	}
+
+	// record all referenced packages as imports
+	list := append(([]*types2.Package)(nil), pkgList[1:]...)
+	sort.Sort(byPath(list))
+	localpkg.SetImports(list)
+
+	// package was imported completely and without errors
+	localpkg.MarkComplete()
+
+	consumed, _ := r.Seek(0, io_SeekCurrent)
+	return int(consumed), localpkg, nil
+}
+
+type iimporter struct {
+	ipath   string
+	version int
+
+	stringData  []byte
+	stringCache map[uint64]string
+	pkgCache    map[uint64]*types2.Package
+
+	declData []byte
+	pkgIndex map[*types2.Package]map[string]uint64
+	typCache map[uint64]types2.Type
+
+	interfaceList []*types2.Interface
+}
+
+func (p *iimporter) doDecl(pkg *types2.Package, name string) {
+	// See if we've already imported this declaration.
+	if obj := pkg.Scope().Lookup(name); obj != nil {
+		return
+	}
+
+	off, ok := p.pkgIndex[pkg][name]
+	if !ok {
+		errorf("%v.%v not in index", pkg, name)
+	}
+
+	r := &importReader{p: p, currPkg: pkg}
+	// Reader.Reset is not available in Go 1.4.
+	// Use bytes.NewReader for now.
+	// r.declReader.Reset(p.declData[off:])
+	r.declReader = *bytes.NewReader(p.declData[off:])
+
+	r.obj(name)
+}
+
+func (p *iimporter) stringAt(off uint64) string {
+	if s, ok := p.stringCache[off]; ok {
+		return s
+	}
+
+	slen, n := binary.Uvarint(p.stringData[off:])
+	if n <= 0 {
+		errorf("varint failed")
+	}
+	spos := off + uint64(n)
+	s := string(p.stringData[spos : spos+slen])
+	p.stringCache[off] = s
+	return s
+}
+
+func (p *iimporter) pkgAt(off uint64) *types2.Package {
+	if pkg, ok := p.pkgCache[off]; ok {
+		return pkg
+	}
+	path := p.stringAt(off)
+	errorf("missing package %q in %q", path, p.ipath)
+	return nil
+}
+
+func (p *iimporter) typAt(off uint64, base *types2.Named) types2.Type {
+	if t, ok := p.typCache[off]; ok && (base == nil || !isInterface(t)) {
+		return t
+	}
+
+	if off < predeclReserved {
+		errorf("predeclared type missing from cache: %v", off)
+	}
+
+	r := &importReader{p: p}
+	// Reader.Reset is not available in Go 1.4.
+	// Use bytes.NewReader for now.
+	// r.declReader.Reset(p.declData[off-predeclReserved:])
+	r.declReader = *bytes.NewReader(p.declData[off-predeclReserved:])
+	t := r.doType(base)
+
+	if base == nil || !isInterface(t) {
+		p.typCache[off] = t
+	}
+	return t
+}
+
+type importReader struct {
+	p          *iimporter
+	declReader bytes.Reader
+	currPkg    *types2.Package
+	prevFile   string
+	prevLine   int64
+	prevColumn int64
+}
+
+func (r *importReader) obj(name string) {
+	tag := r.byte()
+	pos := r.pos()
+
+	switch tag {
+	case 'A':
+		typ := r.typ()
+
+		r.declare(types2.NewTypeName(pos, r.currPkg, name, typ))
+
+	case 'C':
+		typ, val := r.value()
+
+		r.declare(types2.NewConst(pos, r.currPkg, name, typ, val))
+
+	case 'F':
+		sig := r.signature(nil)
+
+		r.declare(types2.NewFunc(pos, r.currPkg, name, sig))
+
+	case 'T':
+		// Types can be recursive. We need to setup a stub
+		// declaration before recursing.
+		obj := types2.NewTypeName(pos, r.currPkg, name, nil)
+		named := types2.NewNamed(obj, nil, nil)
+		r.declare(obj)
+
+		underlying := r.p.typAt(r.uint64(), named).Underlying()
+		named.SetUnderlying(underlying)
+
+		if !isInterface(underlying) {
+			for n := r.uint64(); n > 0; n-- {
+				mpos := r.pos()
+				mname := r.ident()
+				recv := r.param()
+				msig := r.signature(recv)
+
+				named.AddMethod(types2.NewFunc(mpos, r.currPkg, mname, msig))
+			}
+		}
+
+	case 'V':
+		typ := r.typ()
+
+		r.declare(types2.NewVar(pos, r.currPkg, name, typ))
+
+	default:
+		errorf("unexpected tag: %v", tag)
+	}
+}
+
+func (r *importReader) declare(obj types2.Object) {
+	obj.Pkg().Scope().Insert(obj)
+}
+
+func (r *importReader) value() (typ types2.Type, val constant.Value) {
+	typ = r.typ()
+
+	switch b := typ.Underlying().(*types2.Basic); b.Info() & types2.IsConstType {
+	case types2.IsBoolean:
+		val = constant.MakeBool(r.bool())
+
+	case types2.IsString:
+		val = constant.MakeString(r.string())
+
+	case types2.IsInteger:
+		var x big.Int
+		r.mpint(&x, b)
+		val = constant.Make(&x)
+
+	case types2.IsFloat:
+		val = r.mpfloat(b)
+
+	case types2.IsComplex:
+		re := r.mpfloat(b)
+		im := r.mpfloat(b)
+		val = constant.BinaryOp(re, token.ADD, constant.MakeImag(im))
+
+	default:
+		errorf("unexpected type %v", typ) // panics
+		panic("unreachable")
+	}
+
+	return
+}
+
+func intSize(b *types2.Basic) (signed bool, maxBytes uint) {
+	if (b.Info() & types2.IsUntyped) != 0 {
+		return true, 64
+	}
+
+	switch b.Kind() {
+	case types2.Float32, types2.Complex64:
+		return true, 3
+	case types2.Float64, types2.Complex128:
+		return true, 7
+	}
+
+	signed = (b.Info() & types2.IsUnsigned) == 0
+	switch b.Kind() {
+	case types2.Int8, types2.Uint8:
+		maxBytes = 1
+	case types2.Int16, types2.Uint16:
+		maxBytes = 2
+	case types2.Int32, types2.Uint32:
+		maxBytes = 4
+	default:
+		maxBytes = 8
+	}
+
+	return
+}
+
+func (r *importReader) mpint(x *big.Int, typ *types2.Basic) {
+	signed, maxBytes := intSize(typ)
+
+	maxSmall := 256 - maxBytes
+	if signed {
+		maxSmall = 256 - 2*maxBytes
+	}
+	if maxBytes == 1 {
+		maxSmall = 256
+	}
+
+	n, _ := r.declReader.ReadByte()
+	if uint(n) < maxSmall {
+		v := int64(n)
+		if signed {
+			v >>= 1
+			if n&1 != 0 {
+				v = ^v
+			}
+		}
+		x.SetInt64(v)
+		return
+	}
+
+	v := -n
+	if signed {
+		v = -(n &^ 1) >> 1
+	}
+	if v < 1 || uint(v) > maxBytes {
+		errorf("weird decoding: %v, %v => %v", n, signed, v)
+	}
+	b := make([]byte, v)
+	io.ReadFull(&r.declReader, b)
+	x.SetBytes(b)
+	if signed && n&1 != 0 {
+		x.Neg(x)
+	}
+}
+
+func (r *importReader) mpfloat(typ *types2.Basic) constant.Value {
+	var mant big.Int
+	r.mpint(&mant, typ)
+	var f big.Float
+	f.SetInt(&mant)
+	if f.Sign() != 0 {
+		f.SetMantExp(&f, int(r.int64()))
+	}
+	return constant.Make(&f)
+}
+
+func (r *importReader) ident() string {
+	return r.string()
+}
+
+func (r *importReader) qualifiedIdent() (*types2.Package, string) {
+	name := r.string()
+	pkg := r.pkg()
+	return pkg, name
+}
+
+func (r *importReader) pos() syntax.Pos {
+	if r.p.version >= 1 {
+		r.posv1()
+	} else {
+		r.posv0()
+	}
+
+	if r.prevFile == "" && r.prevLine == 0 && r.prevColumn == 0 {
+		return syntax.Pos{}
+	}
+	// TODO(gri) fix this
+	// return r.p.fake.pos(r.prevFile, int(r.prevLine), int(r.prevColumn))
+	return syntax.Pos{}
+}
+
+func (r *importReader) posv0() {
+	delta := r.int64()
+	if delta != deltaNewFile {
+		r.prevLine += delta
+	} else if l := r.int64(); l == -1 {
+		r.prevLine += deltaNewFile
+	} else {
+		r.prevFile = r.string()
+		r.prevLine = l
+	}
+}
+
+func (r *importReader) posv1() {
+	delta := r.int64()
+	r.prevColumn += delta >> 1
+	if delta&1 != 0 {
+		delta = r.int64()
+		r.prevLine += delta >> 1
+		if delta&1 != 0 {
+			r.prevFile = r.string()
+		}
+	}
+}
+
+func (r *importReader) typ() types2.Type {
+	return r.p.typAt(r.uint64(), nil)
+}
+
+func isInterface(t types2.Type) bool {
+	_, ok := t.(*types2.Interface)
+	return ok
+}
+
+func (r *importReader) pkg() *types2.Package { return r.p.pkgAt(r.uint64()) }
+func (r *importReader) string() string       { return r.p.stringAt(r.uint64()) }
+
+func (r *importReader) doType(base *types2.Named) types2.Type {
+	switch k := r.kind(); k {
+	default:
+		errorf("unexpected kind tag in %q: %v", r.p.ipath, k)
+		return nil
+
+	case definedType:
+		pkg, name := r.qualifiedIdent()
+		r.p.doDecl(pkg, name)
+		return pkg.Scope().Lookup(name).(*types2.TypeName).Type()
+	case pointerType:
+		return types2.NewPointer(r.typ())
+	case sliceType:
+		return types2.NewSlice(r.typ())
+	case arrayType:
+		n := r.uint64()
+		return types2.NewArray(r.typ(), int64(n))
+	case chanType:
+		dir := chanDir(int(r.uint64()))
+		return types2.NewChan(dir, r.typ())
+	case mapType:
+		return types2.NewMap(r.typ(), r.typ())
+	case signatureType:
+		r.currPkg = r.pkg()
+		return r.signature(nil)
+
+	case structType:
+		r.currPkg = r.pkg()
+
+		fields := make([]*types2.Var, r.uint64())
+		tags := make([]string, len(fields))
+		for i := range fields {
+			fpos := r.pos()
+			fname := r.ident()
+			ftyp := r.typ()
+			emb := r.bool()
+			tag := r.string()
+
+			fields[i] = types2.NewField(fpos, r.currPkg, fname, ftyp, emb)
+			tags[i] = tag
+		}
+		return types2.NewStruct(fields, tags)
+
+	case interfaceType:
+		r.currPkg = r.pkg()
+
+		embeddeds := make([]types2.Type, r.uint64())
+		for i := range embeddeds {
+			_ = r.pos()
+			embeddeds[i] = r.typ()
+		}
+
+		methods := make([]*types2.Func, r.uint64())
+		for i := range methods {
+			mpos := r.pos()
+			mname := r.ident()
+
+			// TODO(mdempsky): Matches bimport.go, but I
+			// don't agree with this.
+			var recv *types2.Var
+			if base != nil {
+				recv = types2.NewVar(syntax.Pos{}, r.currPkg, "", base)
+			}
+
+			msig := r.signature(recv)
+			methods[i] = types2.NewFunc(mpos, r.currPkg, mname, msig)
+		}
+
+		typ := types2.NewInterfaceType(methods, embeddeds)
+		r.p.interfaceList = append(r.p.interfaceList, typ)
+		return typ
+	}
+}
+
+func (r *importReader) kind() itag {
+	return itag(r.uint64())
+}
+
+func (r *importReader) signature(recv *types2.Var) *types2.Signature {
+	params := r.paramList()
+	results := r.paramList()
+	variadic := params.Len() > 0 && r.bool()
+	return types2.NewSignature(recv, params, results, variadic)
+}
+
+func (r *importReader) paramList() *types2.Tuple {
+	xs := make([]*types2.Var, r.uint64())
+	for i := range xs {
+		xs[i] = r.param()
+	}
+	return types2.NewTuple(xs...)
+}
+
+func (r *importReader) param() *types2.Var {
+	pos := r.pos()
+	name := r.ident()
+	typ := r.typ()
+	return types2.NewParam(pos, r.currPkg, name, typ)
+}
+
+func (r *importReader) bool() bool {
+	return r.uint64() != 0
+}
+
+func (r *importReader) int64() int64 {
+	n, err := binary.ReadVarint(&r.declReader)
+	if err != nil {
+		errorf("readVarint: %v", err)
+	}
+	return n
+}
+
+func (r *importReader) uint64() uint64 {
+	n, err := binary.ReadUvarint(&r.declReader)
+	if err != nil {
+		errorf("readUvarint: %v", err)
+	}
+	return n
+}
+
+func (r *importReader) byte() byte {
+	x, err := r.declReader.ReadByte()
+	if err != nil {
+		errorf("declReader.ReadByte: %v", err)
+	}
+	return x
+}

src/cmd/compile/internal/importer/support.go

@@ -0,0 +1,128 @@
+// UNREVIEWED
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file implements support functionality for iimport.go.
+
+package importer
+
+import (
+	"cmd/compile/internal/types2"
+	"fmt"
+	"go/token"
+	"sync"
+)
+
+func errorf(format string, args ...interface{}) {
+	panic(fmt.Sprintf(format, args...))
+}
+
+const deltaNewFile = -64 // see cmd/compile/internal/gc/bexport.go
+
+// Synthesize a token.Pos
+type fakeFileSet struct {
+	fset  *token.FileSet
+	files map[string]*token.File
+}
+
+func (s *fakeFileSet) pos(file string, line, column int) token.Pos {
+	// TODO(mdempsky): Make use of column.
+
+	// Since we don't know the set of needed file positions, we
+	// reserve maxlines positions per file.
+	const maxlines = 64 * 1024
+	f := s.files[file]
+	if f == nil {
+		f = s.fset.AddFile(file, -1, maxlines)
+		s.files[file] = f
+		// Allocate the fake linebreak indices on first use.
+		// TODO(adonovan): opt: save ~512KB using a more complex scheme?
+		fakeLinesOnce.Do(func() {
+			fakeLines = make([]int, maxlines)
+			for i := range fakeLines {
+				fakeLines[i] = i
+			}
+		})
+		f.SetLines(fakeLines)
+	}
+
+	if line > maxlines {
+		line = 1
+	}
+
+	// Treat the file as if it contained only newlines
+	// and column=1: use the line number as the offset.
+	return f.Pos(line - 1)
+}
+
+var (
+	fakeLines     []int
+	fakeLinesOnce sync.Once
+)
+
+func chanDir(d int) types2.ChanDir {
+	// tag values must match the constants in cmd/compile/internal/gc/go.go
+	switch d {
+	case 1 /* Crecv */ :
+		return types2.RecvOnly
+	case 2 /* Csend */ :
+		return types2.SendOnly
+	case 3 /* Cboth */ :
+		return types2.SendRecv
+	default:
+		errorf("unexpected channel dir %d", d)
+		return 0
+	}
+}
+
+var predeclared = []types2.Type{
+	// basic types
+	types2.Typ[types2.Bool],
+	types2.Typ[types2.Int],
+	types2.Typ[types2.Int8],
+	types2.Typ[types2.Int16],
+	types2.Typ[types2.Int32],
+	types2.Typ[types2.Int64],
+	types2.Typ[types2.Uint],
+	types2.Typ[types2.Uint8],
+	types2.Typ[types2.Uint16],
+	types2.Typ[types2.Uint32],
+	types2.Typ[types2.Uint64],
+	types2.Typ[types2.Uintptr],
+	types2.Typ[types2.Float32],
+	types2.Typ[types2.Float64],
+	types2.Typ[types2.Complex64],
+	types2.Typ[types2.Complex128],
+	types2.Typ[types2.String],
+
+	// basic type aliases
+	types2.Universe.Lookup("byte").Type(),
+	types2.Universe.Lookup("rune").Type(),
+
+	// error
+	types2.Universe.Lookup("error").Type(),
+
+	// untyped types
+	types2.Typ[types2.UntypedBool],
+	types2.Typ[types2.UntypedInt],
+	types2.Typ[types2.UntypedRune],
+	types2.Typ[types2.UntypedFloat],
+	types2.Typ[types2.UntypedComplex],
+	types2.Typ[types2.UntypedString],
+	types2.Typ[types2.UntypedNil],
+
+	// package unsafe
+	types2.Typ[types2.UnsafePointer],
+
+	// invalid type
+	types2.Typ[types2.Invalid], // only appears in packages with errors
+
+	// used internally by gc; never used by this package or in .a files
+	anyType{},
+}
+
+type anyType struct{}
+
+func (t anyType) Underlying() types2.Type { return t }
+func (t anyType) String() string          { return "any" }

src/cmd/compile/internal/importer/testdata/a.go

@@ -0,0 +1,15 @@
+// UNREVIEWED
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Input for TestIssue13566
+
+package a
+
+import "encoding/json"
+
+type A struct {
+	a    *A
+	json json.RawMessage
+}

src/cmd/compile/internal/importer/testdata/b.go

@@ -0,0 +1,12 @@
+// UNREVIEWED
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Input for TestIssue13566
+
+package b
+
+import "./a"
+
+type A a.A

src/cmd/compile/internal/importer/testdata/exports.go

@@ -0,0 +1,89 @@
+// UNREVIEWED
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file is used to generate an object file which
+// serves as test file for gcimporter_test.go.
+
+package exports
+
+import "go/ast"
+
+// Issue 3682: Correctly read dotted identifiers from export data.
+const init1 = 0
+
+func init() {}
+
+const (
+	C0 int = 0
+	C1     = 3.14159265
+	C2     = 2.718281828i
+	C3     = -123.456e-789
+	C4     = +123.456e+789
+	C5     = 1234i
+	C6     = "foo\n"
+	C7     = `bar\n`
+)
+
+type (
+	T1  int
+	T2  [10]int
+	T3  []int
+	T4  *int
+	T5  chan int
+	T6a chan<- int
+	T6b chan (<-chan int)
+	T6c chan<- (chan int)
+	T7  <-chan *ast.File
+	T8  struct{}
+	T9  struct {
+		a    int
+		b, c float32
+		d    []string `go:"tag"`
+	}
+	T10 struct {
+		T8
+		T9
+		_ *T10
+	}
+	T11 map[int]string
+	T12 interface{}
+	T13 interface {
+		m1()
+		m2(int) float32
+	}
+	T14 interface {
+		T12
+		T13
+		m3(x ...struct{}) []T9
+	}
+	T15 func()
+	T16 func(int)
+	T17 func(x int)
+	T18 func() float32
+	T19 func() (x float32)
+	T20 func(...interface{})
+	T21 struct{ next *T21 }
+	T22 struct{ link *T23 }
+	T23 struct{ link *T22 }
+	T24 *T24
+	T25 *T26
+	T26 *T27
+	T27 *T25
+	T28 func(T28) T28
+)
+
+var (
+	V0 int
+	V1         = -991.0
+	V2 float32 = 1.2
+)
+
+func F1()         {}
+func F2(x int)    {}
+func F3() int     { return 0 }
+func F4() float32 { return 0 }
+func F5(a, b, c int, u, v, w struct{ x, y T1 }, more ...interface{}) (p, q, r chan<- T10)
+
+func (p *T1) M1()

src/cmd/compile/internal/importer/testdata/issue15920.go

@@ -0,0 +1,12 @@
+// UNREVIEWED
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+// The underlying type of Error is the underlying type of error.
+// Make sure we can import this again without problems.
+type Error error
+
+func F() Error { return nil }

src/cmd/compile/internal/importer/testdata/issue20046.go

@@ -0,0 +1,10 @@
+// UNREVIEWED
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+var V interface {
+	M()
+}

src/cmd/compile/internal/importer/testdata/issue25301.go

@@ -0,0 +1,18 @@
+// UNREVIEWED
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package issue25301
+
+type (
+	A = interface {
+		M()
+	}
+	T interface {
+		A
+	}
+	S struct{}
+)
+
+func (S) M() { println("m") }

src/cmd/compile/internal/importer/testdata/issue25596.go

@@ -0,0 +1,14 @@
+// UNREVIEWED
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package issue25596
+
+type E interface {
+	M() T
+}
+
+type T interface {
+	E
+}

src/cmd/compile/internal/importer/testdata/p.go

@@ -0,0 +1,14 @@
+// UNREVIEWED
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Input for TestIssue15517
+
+package p
+
+const C = 0
+
+var V int
+
+func F() {}

src/cmd/compile/internal/importer/testdata/versions/test.go

@@ -0,0 +1,29 @@
+// UNREVIEWED
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// To create a test case for a new export format version,
+// build this package with the latest compiler and store
+// the resulting .a file appropriately named in the versions
+// directory. The VersionHandling test will pick it up.
+//
+// In the testdata/versions:
+//
+// go build -o test_go1.$X_$Y.a test.go
+//
+// with $X = Go version and $Y = export format version
+// (add 'b' or 'i' to distinguish between binary and
+// indexed format starting with 1.11 as long as both
+// formats are supported).
+//
+// Make sure this source is extended such that it exercises
+// whatever export format change has taken place.
+
+package test
+
+// Any release before and including Go 1.7 didn't encode
+// the package for a blank struct field.
+type BlankField struct {
+	_ int
+}

src/cmd/compile/internal/inline/inl.go

@@ -354,8 +354,13 @@ func (v *hairyVisitor) doNode(n ir.Node) bool {
 		return true
 
 	case ir.OCLOSURE:
-		// TODO(danscales) - fix some bugs when budget is lowered below 15
-		// Maybe make budget proportional to number of closure variables, e.g.:
+		if base.Debug.InlFuncsWithClosures == 0 {
+			v.reason = "not inlining functions with closures"
+			return true
+		}
+
+		// TODO(danscales): Maybe make budget proportional to number of closure
+		// variables, e.g.:
 		//v.budget -= int32(len(n.(*ir.ClosureExpr).Func.ClosureVars) * 3)
 		v.budget -= 15
 		// Scan body of closure (which DoChildren doesn't automatically
@@ -377,6 +382,22 @@ func (v *hairyVisitor) doNode(n ir.Node) bool {
 	case ir.OAPPEND:
 		v.budget -= inlineExtraAppendCost
 
+	case ir.ODEREF:
+		// *(*X)(unsafe.Pointer(&x)) is low-cost
+		n := n.(*ir.StarExpr)
+
+		ptr := n.X
+		for ptr.Op() == ir.OCONVNOP {
+			ptr = ptr.(*ir.ConvExpr).X
+		}
+		if ptr.Op() == ir.OADDR {
+			v.budget += 1 // undo half of default cost of ir.ODEREF+ir.OADDR
+		}
+
+	case ir.OCONVNOP:
+		// This doesn't produce code, but the children might.
+		v.budget++ // undo default cost
+
 	case ir.ODCLCONST, ir.OFALL:
 		// These nodes don't produce code; omit from inlining budget.
 		return false
@@ -829,17 +850,25 @@ func mkinlcall(n *ir.CallExpr, fn *ir.Func, maxCost int32, inlMap map[*ir.Func]b
 		}
 	}
 
+	// We can delay declaring+initializing result parameters if:
+	// (1) there's exactly one "return" statement in the inlined function;
+	// (2) it's not an empty return statement (#44355); and
+	// (3) the result parameters aren't named.
+	delayretvars := true
+
 	nreturns := 0
 	ir.VisitList(ir.Nodes(fn.Inl.Body), func(n ir.Node) {
-		if n != nil && n.Op() == ir.ORETURN {
+		if n, ok := n.(*ir.ReturnStmt); ok {
 			nreturns++
+			if len(n.Results) == 0 {
+				delayretvars = false // empty return statement (case 2)
+			}
 		}
 	})
 
-	// We can delay declaring+initializing result parameters if:
-	// (1) there's only one "return" statement in the inlined
-	// function, and (2) the result parameters aren't named.
-	delayretvars := nreturns == 1
+	if nreturns != 1 {
+		delayretvars = false // not exactly one return statement (case 1)
+	}
 
 	// temporaries for return values.
 	var retvars []ir.Node
@@ -850,7 +879,7 @@ func mkinlcall(n *ir.CallExpr, fn *ir.Func, maxCost int32, inlMap map[*ir.Func]b
 			m = inlvar(n)
 			m = typecheck.Expr(m).(*ir.Name)
 			inlvars[n] = m
-			delayretvars = false // found a named result parameter
+			delayretvars = false // found a named result parameter (case 3)
 		} else {
 			// anonymous return values, synthesize names for use in assignment that replaces return
 			m = retvar(t, i)
@@ -1221,7 +1250,7 @@ func (subst *inlsubst) closure(n *ir.ClosureExpr) ir.Node {
 		newrecv = newrecvs[0]
 	}
 	newt := types.NewSignature(oldt.Pkg(), newrecv,
-		subst.fields(oldt.Params()), subst.fields(oldt.Results()))
+		nil, subst.fields(oldt.Params()), subst.fields(oldt.Results()))
 
 	newfn.Nname.SetType(newt)
 	newfn.Body = subst.list(oldfn.Body)

src/cmd/compile/internal/ir/class_string.go

@@ -14,12 +14,13 @@ func _() {
 	_ = x[PAUTOHEAP-3]
 	_ = x[PPARAM-4]
 	_ = x[PPARAMOUT-5]
-	_ = x[PFUNC-6]
+	_ = x[PTYPEPARAM-6]
+	_ = x[PFUNC-7]
 }
 
-const _Class_name = "PxxxPEXTERNPAUTOPAUTOHEAPPPARAMPPARAMOUTPFUNC"
+const _Class_name = "PxxxPEXTERNPAUTOPAUTOHEAPPPARAMPPARAMOUTPTYPEPARAMPFUNC"
 
-var _Class_index = [...]uint8{0, 4, 11, 16, 25, 31, 40, 45}
+var _Class_index = [...]uint8{0, 4, 11, 16, 25, 31, 40, 50, 55}
 
 func (i Class) String() string {
 	if i >= Class(len(_Class_index)-1) {

src/cmd/compile/internal/ir/expr.go

@@ -447,14 +447,14 @@ func (n *ParenExpr) SetOTYPE(t *types.Type) {
 	t.SetNod(n)
 }
 
-// A ResultExpr represents a direct access to a result slot on the stack frame.
+// A ResultExpr represents a direct access to a result.
 type ResultExpr struct {
 	miniExpr
-	Offset int64
+	Index int64 // index of the result expr.
 }
 
-func NewResultExpr(pos src.XPos, typ *types.Type, offset int64) *ResultExpr {
-	n := &ResultExpr{Offset: offset}
+func NewResultExpr(pos src.XPos, typ *types.Type, index int64) *ResultExpr {
+	n := &ResultExpr{Index: index}
 	n.pos = pos
 	n.op = ORESULT
 	n.typ = typ
@@ -670,6 +670,20 @@ func (n *UnaryExpr) SetOp(op Op) {
 	}
 }
 
+// An InstExpr is a generic function or type instantiation.
+type InstExpr struct {
+	miniExpr
+	X     Node
+	Targs []Node
+}
+
+func NewInstExpr(pos src.XPos, op Op, x Node, targs []Node) *InstExpr {
+	n := &InstExpr{X: x, Targs: targs}
+	n.pos = pos
+	n.op = op
+	return n
+}
+
 func IsZero(n Node) bool {
 	switch n.Op() {
 	case ONIL:

src/cmd/compile/internal/ir/mknode.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build ignore
 // +build ignore
 
 package main

src/cmd/compile/internal/ir/name.go

@@ -398,7 +398,7 @@ func FinishCaptureNames(pos src.XPos, outerfn, fn *Func) {
 	// unhook them.
 	// make the list of pointers for the closure call.
 	for _, cv := range fn.ClosureVars {
-		// Unlink from n; see comment in syntax.go type Param for these fields.
+		// Unlink from n; see comment above on type Name for these fields.
 		n := cv.Defn.(*Name)
 		n.Innermost = cv.Outer
 
@@ -473,13 +473,14 @@ type Class uint8
 
 //go:generate stringer -type=Class name.go
 const (
-	Pxxx      Class = iota // no class; used during ssa conversion to indicate pseudo-variables
-	PEXTERN                // global variables
-	PAUTO                  // local variables
-	PAUTOHEAP              // local variables or parameters moved to heap
-	PPARAM                 // input arguments
-	PPARAMOUT              // output results
-	PFUNC                  // global functions
+	Pxxx       Class = iota // no class; used during ssa conversion to indicate pseudo-variables
+	PEXTERN                 // global variables
+	PAUTO                   // local variables
+	PAUTOHEAP               // local variables or parameters moved to heap
+	PPARAM                  // input arguments
+	PPARAMOUT               // output results
+	PTYPEPARAM              // type params
+	PFUNC                   // global functions
 
 	// Careful: Class is stored in three bits in Node.flags.
 	_ = uint((1 << 3) - iota) // static assert for iota <= (1 << 3)

src/cmd/compile/internal/ir/node.go

@@ -278,6 +278,8 @@ const (
 	// OTYPESW:  Left := Right.(type) (appears as .Left of OSWITCH)
 	//   Left is nil if there is no type-switch variable
 	OTYPESW
+	OFUNCINST // instantiation of a generic function
+	OTYPEINST // instantiation of a generic type
 
 	// types
 	OTCHAN   // chan int
@@ -454,7 +456,7 @@ const (
 	// Go command pragmas
 	GoBuildPragma
 
-	RegisterParams // TODO remove after register abi is working
+	RegisterParams // TODO(register args) remove after register abi is working
 
 )
 

src/cmd/compile/internal/ir/node_gen.go

@@ -669,6 +669,33 @@ func (n *InlinedCallExpr) editChildren(edit func(Node) Node) {
 	editNodes(n.ReturnVars, edit)
 }
 
+func (n *InstExpr) Format(s fmt.State, verb rune) { fmtNode(n, s, verb) }
+func (n *InstExpr) copy() Node {
+	c := *n
+	c.init = copyNodes(c.init)
+	c.Targs = copyNodes(c.Targs)
+	return &c
+}
+func (n *InstExpr) doChildren(do func(Node) bool) bool {
+	if doNodes(n.init, do) {
+		return true
+	}
+	if n.X != nil && do(n.X) {
+		return true
+	}
+	if doNodes(n.Targs, do) {
+		return true
+	}
+	return false
+}
+func (n *InstExpr) editChildren(edit func(Node) Node) {
+	editNodes(n.init, edit)
+	if n.X != nil {
+		n.X = edit(n.X).(Node)
+	}
+	editNodes(n.Targs, edit)
+}
+
 func (n *InterfaceType) Format(s fmt.State, verb rune) { fmtNode(n, s, verb) }
 func (n *InterfaceType) copy() Node {
 	c := *n

src/cmd/compile/internal/ir/op_string.go

@@ -137,34 +137,36 @@ func _() {
 	_ = x[OSELECT-126]
 	_ = x[OSWITCH-127]
 	_ = x[OTYPESW-128]
-	_ = x[OTCHAN-129]
-	_ = x[OTMAP-130]
-	_ = x[OTSTRUCT-131]
-	_ = x[OTINTER-132]
-	_ = x[OTFUNC-133]
-	_ = x[OTARRAY-134]
-	_ = x[OTSLICE-135]
-	_ = x[OINLCALL-136]
-	_ = x[OEFACE-137]
-	_ = x[OITAB-138]
-	_ = x[OIDATA-139]
-	_ = x[OSPTR-140]
-	_ = x[OCFUNC-141]
-	_ = x[OCHECKNIL-142]
-	_ = x[OVARDEF-143]
-	_ = x[OVARKILL-144]
-	_ = x[OVARLIVE-145]
-	_ = x[ORESULT-146]
-	_ = x[OINLMARK-147]
-	_ = x[OLINKSYMOFFSET-148]
-	_ = x[OTAILCALL-149]
-	_ = x[OGETG-150]
-	_ = x[OEND-151]
+	_ = x[OFUNCINST-129]
+	_ = x[OTYPEINST-130]
+	_ = x[OTCHAN-131]
+	_ = x[OTMAP-132]
+	_ = x[OTSTRUCT-133]
+	_ = x[OTINTER-134]
+	_ = x[OTFUNC-135]
+	_ = x[OTARRAY-136]
+	_ = x[OTSLICE-137]
+	_ = x[OINLCALL-138]
+	_ = x[OEFACE-139]
+	_ = x[OITAB-140]
+	_ = x[OIDATA-141]
+	_ = x[OSPTR-142]
+	_ = x[OCFUNC-143]
+	_ = x[OCHECKNIL-144]
+	_ = x[OVARDEF-145]
+	_ = x[OVARKILL-146]
+	_ = x[OVARLIVE-147]
+	_ = x[ORESULT-148]
+	_ = x[OINLMARK-149]
+	_ = x[OLINKSYMOFFSET-150]
+	_ = x[OTAILCALL-151]
+	_ = x[OGETG-152]
+	_ = x[OEND-153]
 }
 
-const _Op_name = "XXXNAMENONAMETYPEPACKLITERALNILADDSUBORXORADDSTRADDRANDANDAPPENDBYTES2STRBYTES2STRTMPRUNES2STRSTR2BYTESSTR2BYTESTMPSTR2RUNESASAS2AS2DOTTYPEAS2FUNCAS2MAPRAS2RECVASOPCALLCALLFUNCCALLMETHCALLINTERCALLPARTCAPCLOSECLOSURECOMPLITMAPLITSTRUCTLITARRAYLITSLICELITPTRLITCONVCONVIFACECONVNOPCOPYDCLDCLFUNCDCLCONSTDCLTYPEDELETEDOTDOTPTRDOTMETHDOTINTERXDOTDOTTYPEDOTTYPE2EQNELTLEGEGTDEREFINDEXINDEXMAPKEYSTRUCTKEYLENMAKEMAKECHANMAKEMAPMAKESLICEMAKESLICECOPYMULDIVMODLSHRSHANDANDNOTNEWNOTBITNOTPLUSNEGORORPANICPRINTPRINTNPARENSENDSLICESLICEARRSLICESTRSLICE3SLICE3ARRSLICEHEADERRECOVERRECVRUNESTRSELRECV2IOTAREALIMAGCOMPLEXALIGNOFOFFSETOFSIZEOFMETHEXPRSTMTEXPRBLOCKBREAKCASECONTINUEDEFERFALLFORFORUNTILGOTOIFLABELGORANGERETURNSELECTSWITCHTYPESWTCHANTMAPTSTRUCTTINTERTFUNCTARRAYTSLICEINLCALLEFACEITABIDATASPTRCFUNCCHECKNILVARDEFVARKILLVARLIVERESULTINLMARKLINKSYMOFFSETTAILCALLGETGEND"
+const _Op_name = "XXXNAMENONAMETYPEPACKLITERALNILADDSUBORXORADDSTRADDRANDANDAPPENDBYTES2STRBYTES2STRTMPRUNES2STRSTR2BYTESSTR2BYTESTMPSTR2RUNESASAS2AS2DOTTYPEAS2FUNCAS2MAPRAS2RECVASOPCALLCALLFUNCCALLMETHCALLINTERCALLPARTCAPCLOSECLOSURECOMPLITMAPLITSTRUCTLITARRAYLITSLICELITPTRLITCONVCONVIFACECONVNOPCOPYDCLDCLFUNCDCLCONSTDCLTYPEDELETEDOTDOTPTRDOTMETHDOTINTERXDOTDOTTYPEDOTTYPE2EQNELTLEGEGTDEREFINDEXINDEXMAPKEYSTRUCTKEYLENMAKEMAKECHANMAKEMAPMAKESLICEMAKESLICECOPYMULDIVMODLSHRSHANDANDNOTNEWNOTBITNOTPLUSNEGORORPANICPRINTPRINTNPARENSENDSLICESLICEARRSLICESTRSLICE3SLICE3ARRSLICEHEADERRECOVERRECVRUNESTRSELRECV2IOTAREALIMAGCOMPLEXALIGNOFOFFSETOFSIZEOFMETHEXPRSTMTEXPRBLOCKBREAKCASECONTINUEDEFERFALLFORFORUNTILGOTOIFLABELGORANGERETURNSELECTSWITCHTYPESWFUNCINSTTYPEINSTTCHANTMAPTSTRUCTTINTERTFUNCTARRAYTSLICEINLCALLEFACEITABIDATASPTRCFUNCCHECKNILVARDEFVARKILLVARLIVERESULTINLMARKLINKSYMOFFSETTAILCALLGETGEND"
 
-var _Op_index = [...]uint16{0, 3, 7, 13, 17, 21, 28, 31, 34, 37, 39, 42, 48, 52, 58, 64, 73, 85, 94, 103, 115, 124, 126, 129, 139, 146, 153, 160, 164, 168, 176, 184, 193, 201, 204, 209, 216, 223, 229, 238, 246, 254, 260, 264, 273, 280, 284, 287, 294, 302, 309, 315, 318, 324, 331, 339, 343, 350, 358, 360, 362, 364, 366, 368, 370, 375, 380, 388, 391, 400, 403, 407, 415, 422, 431, 444, 447, 450, 453, 456, 459, 462, 468, 471, 474, 480, 484, 487, 491, 496, 501, 507, 512, 516, 521, 529, 537, 543, 552, 563, 570, 574, 581, 589, 593, 597, 601, 608, 615, 623, 629, 637, 645, 650, 655, 659, 667, 672, 676, 679, 687, 691, 693, 698, 700, 705, 711, 717, 723, 729, 734, 738, 745, 751, 756, 762, 768, 775, 780, 784, 789, 793, 798, 806, 812, 819, 826, 832, 839, 852, 860, 864, 867}
+var _Op_index = [...]uint16{0, 3, 7, 13, 17, 21, 28, 31, 34, 37, 39, 42, 48, 52, 58, 64, 73, 85, 94, 103, 115, 124, 126, 129, 139, 146, 153, 160, 164, 168, 176, 184, 193, 201, 204, 209, 216, 223, 229, 238, 246, 254, 260, 264, 273, 280, 284, 287, 294, 302, 309, 315, 318, 324, 331, 339, 343, 350, 358, 360, 362, 364, 366, 368, 370, 375, 380, 388, 391, 400, 403, 407, 415, 422, 431, 444, 447, 450, 453, 456, 459, 462, 468, 471, 474, 480, 484, 487, 491, 496, 501, 507, 512, 516, 521, 529, 537, 543, 552, 563, 570, 574, 581, 589, 593, 597, 601, 608, 615, 623, 629, 637, 645, 650, 655, 659, 667, 672, 676, 679, 687, 691, 693, 698, 700, 705, 711, 717, 723, 729, 737, 745, 750, 754, 761, 767, 772, 778, 784, 791, 796, 800, 805, 809, 814, 822, 828, 835, 842, 848, 855, 868, 876, 880, 883}
 
 func (i Op) String() string {
 	if i >= Op(len(_Op_index)-1) {

src/cmd/compile/internal/ir/package.go

@@ -32,4 +32,7 @@ type Package struct {
 
 	// Exported (or re-exported) symbols.
 	Exports []*Name
+
+	// Map from function names of stencils to already-created stencils.
+	Stencils map[*types.Sym]*Func
 }

src/cmd/compile/internal/ir/visit.go

@@ -25,10 +25,10 @@ package ir
 //
 //	var do func(ir.Node) bool
 //	do = func(x ir.Node) bool {
-//		... processing BEFORE visting children ...
+//		... processing BEFORE visiting children ...
 //		if ... should visit children ... {
 //			ir.DoChildren(x, do)
-//			... processing AFTER visting children ...
+//			... processing AFTER visiting children ...
 //		}
 //		if ... should stop parent DoChildren call from visiting siblings ... {
 //			return true
@@ -43,11 +43,11 @@ package ir
 //
 //	var do func(ir.Node) bool
 //	do = func(x ir.Node) bool {
-//		... processing BEFORE visting children ...
+//		... processing BEFORE visiting children ...
 //		if ... should visit children ... {
 //			ir.DoChildren(x, do)
 //		}
-//		... processing AFTER visting children ...
+//		... processing AFTER visiting children ...
 //		return false
 //	}
 //	do(root)

src/cmd/compile/internal/logopt/escape.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build go1.8
 // +build go1.8
 
 package logopt

src/cmd/compile/internal/logopt/escape_bootstrap.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build !go1.8
 // +build !go1.8
 
 package logopt

src/cmd/compile/internal/mips/ssa.go

@@ -112,9 +112,6 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 			p.To.Reg = y
 		}
 	case ssa.OpMIPSMOVWnop:
-		if v.Reg() != v.Args[0].Reg() {
-			v.Fatalf("input[0] and output not in same register %s", v.LongString())
-		}
 		// nothing to do
 	case ssa.OpLoadReg:
 		if v.Type.IsFlags() {
@@ -244,9 +241,6 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = v.Reg()
 	case ssa.OpMIPSCMOVZ:
-		if v.Reg() != v.Args[0].Reg() {
-			v.Fatalf("input[0] and output not in same register %s", v.LongString())
-		}
 		p := s.Prog(v.Op.Asm())
 		p.From.Type = obj.TYPE_REG
 		p.From.Reg = v.Args[2].Reg()
@@ -254,9 +248,6 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = v.Reg()
 	case ssa.OpMIPSCMOVZzero:
-		if v.Reg() != v.Args[0].Reg() {
-			v.Fatalf("input[0] and output not in same register %s", v.LongString())
-		}
 		p := s.Prog(v.Op.Asm())
 		p.From.Type = obj.TYPE_REG
 		p.From.Reg = v.Args[1].Reg()
@@ -372,6 +363,7 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		ssa.OpMIPSMOVDF,
 		ssa.OpMIPSNEGF,
 		ssa.OpMIPSNEGD,
+		ssa.OpMIPSSQRTF,
 		ssa.OpMIPSSQRTD,
 		ssa.OpMIPSCLZ:
 		p := s.Prog(v.Op.Asm())

src/cmd/compile/internal/mips64/ssa.go

@@ -115,9 +115,6 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 			p.To.Reg = y
 		}
 	case ssa.OpMIPS64MOVVnop:
-		if v.Reg() != v.Args[0].Reg() {
-			v.Fatalf("input[0] and output not in same register %s", v.LongString())
-		}
 		// nothing to do
 	case ssa.OpLoadReg:
 		if v.Type.IsFlags() {
@@ -358,6 +355,7 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		ssa.OpMIPS64MOVDF,
 		ssa.OpMIPS64NEGF,
 		ssa.OpMIPS64NEGD,
+		ssa.OpMIPS64SQRTF,
 		ssa.OpMIPS64SQRTD:
 		p := s.Prog(v.Op.Asm())
 		p.From.Type = obj.TYPE_REG

src/cmd/compile/internal/noder/decl.go

@@ -0,0 +1,241 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package noder
+
+import (
+	"go/constant"
+
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/syntax"
+	"cmd/compile/internal/typecheck"
+	"cmd/compile/internal/types"
+	"cmd/compile/internal/types2"
+)
+
+// TODO(mdempsky): Skip blank declarations? Probably only safe
+// for declarations without pragmas.
+
+func (g *irgen) decls(decls []syntax.Decl) []ir.Node {
+	var res ir.Nodes
+	for _, decl := range decls {
+		switch decl := decl.(type) {
+		case *syntax.ConstDecl:
+			g.constDecl(&res, decl)
+		case *syntax.FuncDecl:
+			g.funcDecl(&res, decl)
+		case *syntax.TypeDecl:
+			if ir.CurFunc == nil {
+				continue // already handled in irgen.generate
+			}
+			g.typeDecl(&res, decl)
+		case *syntax.VarDecl:
+			g.varDecl(&res, decl)
+		default:
+			g.unhandled("declaration", decl)
+		}
+	}
+	return res
+}
+
+func (g *irgen) importDecl(p *noder, decl *syntax.ImportDecl) {
+	// TODO(mdempsky): Merge with gcimports so we don't have to import
+	// packages twice.
+
+	g.pragmaFlags(decl.Pragma, 0)
+
+	ipkg := importfile(decl)
+	if ipkg == ir.Pkgs.Unsafe {
+		p.importedUnsafe = true
+	}
+	if ipkg.Path == "embed" {
+		p.importedEmbed = true
+	}
+}
+
+func (g *irgen) constDecl(out *ir.Nodes, decl *syntax.ConstDecl) {
+	g.pragmaFlags(decl.Pragma, 0)
+
+	for _, name := range decl.NameList {
+		name, obj := g.def(name)
+
+		// For untyped numeric constants, make sure the value
+		// representation matches what the rest of the
+		// compiler (really just iexport) expects.
+		// TODO(mdempsky): Revisit after #43891 is resolved.
+		val := obj.(*types2.Const).Val()
+		switch name.Type() {
+		case types.UntypedInt, types.UntypedRune:
+			val = constant.ToInt(val)
+		case types.UntypedFloat:
+			val = constant.ToFloat(val)
+		case types.UntypedComplex:
+			val = constant.ToComplex(val)
+		}
+		name.SetVal(val)
+
+		out.Append(ir.NewDecl(g.pos(decl), ir.ODCLCONST, name))
+	}
+}
+
+func (g *irgen) funcDecl(out *ir.Nodes, decl *syntax.FuncDecl) {
+	fn := ir.NewFunc(g.pos(decl))
+	fn.Nname, _ = g.def(decl.Name)
+	fn.Nname.Func = fn
+	fn.Nname.Defn = fn
+
+	fn.Pragma = g.pragmaFlags(decl.Pragma, funcPragmas)
+	if fn.Pragma&ir.Systemstack != 0 && fn.Pragma&ir.Nosplit != 0 {
+		base.ErrorfAt(fn.Pos(), "go:nosplit and go:systemstack cannot be combined")
+	}
+
+	if decl.Name.Value == "init" && decl.Recv == nil {
+		g.target.Inits = append(g.target.Inits, fn)
+	}
+
+	g.funcBody(fn, decl.Recv, decl.Type, decl.Body)
+
+	out.Append(fn)
+}
+
+func (g *irgen) typeDecl(out *ir.Nodes, decl *syntax.TypeDecl) {
+	if decl.Alias {
+		name, _ := g.def(decl.Name)
+		g.pragmaFlags(decl.Pragma, 0)
+
+		// TODO(mdempsky): This matches how typecheckdef marks aliases for
+		// export, but this won't generalize to exporting function-scoped
+		// type aliases. We should maybe just use n.Alias() instead.
+		if ir.CurFunc == nil {
+			name.Sym().Def = ir.TypeNode(name.Type())
+		}
+
+		out.Append(ir.NewDecl(g.pos(decl), ir.ODCLTYPE, name))
+		return
+	}
+
+	// Prevent size calculations until we set the underlying type.
+	types.DeferCheckSize()
+
+	name, obj := g.def(decl.Name)
+	ntyp, otyp := name.Type(), obj.Type()
+	if ir.CurFunc != nil {
+		typecheck.TypeGen++
+		ntyp.Vargen = typecheck.TypeGen
+	}
+
+	pragmas := g.pragmaFlags(decl.Pragma, typePragmas)
+	name.SetPragma(pragmas) // TODO(mdempsky): Is this still needed?
+
+	if pragmas&ir.NotInHeap != 0 {
+		ntyp.SetNotInHeap(true)
+	}
+
+	// We need to use g.typeExpr(decl.Type) here to ensure that for
+	// chained, defined-type declarations like
+	//
+	//	type T U
+	//
+	//	//go:notinheap
+	//	type U struct { … }
+	//
+	// that we mark both T and U as NotInHeap. If we instead used just
+	// g.typ(otyp.Underlying()), then we'd instead set T's underlying
+	// type directly to the struct type (which is not marked NotInHeap)
+	// and fail to mark T as NotInHeap.
+	//
+	// Also, we rely here on Type.SetUnderlying allowing passing a
+	// defined type and handling forward references like from T to U
+	// above. Contrast with go/types's Named.SetUnderlying, which
+	// disallows this.
+	//
+	// [mdempsky: Subtleties like these are why I always vehemently
+	// object to new type pragmas.]
+	ntyp.SetUnderlying(g.typeExpr(decl.Type))
+	types.ResumeCheckSize()
+
+	if otyp, ok := otyp.(*types2.Named); ok && otyp.NumMethods() != 0 {
+		methods := make([]*types.Field, otyp.NumMethods())
+		for i := range methods {
+			m := otyp.Method(i)
+			meth := g.obj(m)
+			methods[i] = types.NewField(meth.Pos(), g.selector(m), meth.Type())
+			methods[i].Nname = meth
+		}
+		ntyp.Methods().Set(methods)
+	}
+
+	out.Append(ir.NewDecl(g.pos(decl), ir.ODCLTYPE, name))
+}
+
+func (g *irgen) varDecl(out *ir.Nodes, decl *syntax.VarDecl) {
+	pos := g.pos(decl)
+	names := make([]*ir.Name, len(decl.NameList))
+	for i, name := range decl.NameList {
+		names[i], _ = g.def(name)
+	}
+	values := g.exprList(decl.Values)
+
+	if decl.Pragma != nil {
+		pragma := decl.Pragma.(*pragmas)
+		// TODO(mdempsky): Plumb noder.importedEmbed through to here.
+		varEmbed(g.makeXPos, names[0], decl, pragma, true)
+		g.reportUnused(pragma)
+	}
+
+	var as2 *ir.AssignListStmt
+	if len(values) != 0 && len(names) != len(values) {
+		as2 = ir.NewAssignListStmt(pos, ir.OAS2, make([]ir.Node, len(names)), values)
+	}
+
+	for i, name := range names {
+		if ir.CurFunc != nil {
+			out.Append(ir.NewDecl(pos, ir.ODCL, name))
+		}
+		if as2 != nil {
+			as2.Lhs[i] = name
+			name.Defn = as2
+		} else {
+			as := ir.NewAssignStmt(pos, name, nil)
+			if len(values) != 0 {
+				as.Y = values[i]
+				name.Defn = as
+			} else if ir.CurFunc == nil {
+				name.Defn = as
+			}
+			out.Append(typecheck.Stmt(as))
+		}
+	}
+	if as2 != nil {
+		out.Append(typecheck.Stmt(as2))
+	}
+}
+
+// pragmaFlags returns any specified pragma flags included in allowed,
+// and reports errors about any other, unexpected pragmas.
+func (g *irgen) pragmaFlags(pragma syntax.Pragma, allowed ir.PragmaFlag) ir.PragmaFlag {
+	if pragma == nil {
+		return 0
+	}
+	p := pragma.(*pragmas)
+	present := p.Flag & allowed
+	p.Flag &^= allowed
+	g.reportUnused(p)
+	return present
+}
+
+// reportUnused reports errors about any unused pragmas.
+func (g *irgen) reportUnused(pragma *pragmas) {
+	for _, pos := range pragma.Pos {
+		if pos.Flag&pragma.Flag != 0 {
+			base.ErrorfAt(g.makeXPos(pos.Pos), "misplaced compiler directive")
+		}
+	}
+	if len(pragma.Embeds) > 0 {
+		for _, e := range pragma.Embeds {
+			base.ErrorfAt(g.makeXPos(e.Pos), "misplaced go:embed directive")
+		}
+	}
+}

src/cmd/compile/internal/noder/expr.go

@@ -0,0 +1,368 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package noder
+
+import (
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/syntax"
+	"cmd/compile/internal/typecheck"
+	"cmd/compile/internal/types"
+	"cmd/compile/internal/types2"
+	"cmd/internal/src"
+)
+
+func (g *irgen) expr(expr syntax.Expr) ir.Node {
+	// TODO(mdempsky): Change callers to not call on nil?
+	if expr == nil {
+		return nil
+	}
+
+	if expr, ok := expr.(*syntax.Name); ok && expr.Value == "_" {
+		return ir.BlankNode
+	}
+
+	tv, ok := g.info.Types[expr]
+	if !ok {
+		base.FatalfAt(g.pos(expr), "missing type for %v (%T)", expr, expr)
+	}
+	switch {
+	case tv.IsBuiltin():
+		// TODO(mdempsky): Handle in CallExpr?
+		return g.use(expr.(*syntax.Name))
+	case tv.IsType():
+		return ir.TypeNode(g.typ(tv.Type))
+	case tv.IsValue(), tv.IsVoid():
+		// ok
+	default:
+		base.FatalfAt(g.pos(expr), "unrecognized type-checker result")
+	}
+
+	// The gc backend expects all expressions to have a concrete type, and
+	// types2 mostly satisfies this expectation already. But there are a few
+	// cases where the Go spec doesn't require converting to concrete type,
+	// and so types2 leaves them untyped. So we need to fix those up here.
+	typ := tv.Type
+	if basic, ok := typ.(*types2.Basic); ok && basic.Info()&types2.IsUntyped != 0 {
+		switch basic.Kind() {
+		case types2.UntypedNil:
+			// ok; can appear in type switch case clauses
+			// TODO(mdempsky): Handle as part of type switches instead?
+		case types2.UntypedBool:
+			typ = types2.Typ[types2.Bool] // expression in "if" or "for" condition
+		case types2.UntypedString:
+			typ = types2.Typ[types2.String] // argument to "append" or "copy" calls
+		default:
+			base.FatalfAt(g.pos(expr), "unexpected untyped type: %v", basic)
+		}
+	}
+
+	// Constant expression.
+	if tv.Value != nil {
+		return Const(g.pos(expr), g.typ(typ), tv.Value)
+	}
+
+	n := g.expr0(typ, expr)
+	if n.Typecheck() != 1 {
+		base.FatalfAt(g.pos(expr), "missed typecheck: %+v", n)
+	}
+	if !g.match(n.Type(), typ, tv.HasOk()) {
+		base.FatalfAt(g.pos(expr), "expected %L to have type %v", n, typ)
+	}
+	return n
+}
+
+func (g *irgen) expr0(typ types2.Type, expr syntax.Expr) ir.Node {
+	pos := g.pos(expr)
+
+	switch expr := expr.(type) {
+	case *syntax.Name:
+		if _, isNil := g.info.Uses[expr].(*types2.Nil); isNil {
+			return Nil(pos, g.typ(typ))
+		}
+		// TODO(mdempsky): Remove dependency on typecheck.Expr.
+		return typecheck.Expr(g.use(expr))
+
+	case *syntax.CompositeLit:
+		return g.compLit(typ, expr)
+
+	case *syntax.FuncLit:
+		return g.funcLit(typ, expr)
+
+	case *syntax.AssertExpr:
+		return Assert(pos, g.expr(expr.X), g.typeExpr(expr.Type))
+
+	case *syntax.CallExpr:
+		fun := g.expr(expr.Fun)
+		if inferred, ok := g.info.Inferred[expr]; ok && len(inferred.Targs) > 0 {
+			targs := make([]ir.Node, len(inferred.Targs))
+			for i, targ := range inferred.Targs {
+				targs[i] = ir.TypeNode(g.typ(targ))
+			}
+			if fun.Op() == ir.OFUNCINST {
+				// Replace explicit type args with the full list that
+				// includes the additional inferred type args
+				fun.(*ir.InstExpr).Targs = targs
+			} else {
+				// Create a function instantiation here, given
+				// there are only inferred type args (e.g.
+				// min(5,6), where min is a generic function)
+				inst := ir.NewInstExpr(pos, ir.OFUNCINST, fun, targs)
+				typed(fun.Type(), inst)
+				fun = inst
+			}
+
+		}
+		return Call(pos, g.typ(typ), fun, g.exprs(expr.ArgList), expr.HasDots)
+
+	case *syntax.IndexExpr:
+		var targs []ir.Node
+		if _, ok := expr.Index.(*syntax.ListExpr); ok {
+			targs = g.exprList(expr.Index)
+		} else {
+			index := g.expr(expr.Index)
+			if index.Op() != ir.OTYPE {
+				// This is just a normal index expression
+				return Index(pos, g.expr(expr.X), index)
+			}
+			// This is generic function instantiation with a single type
+			targs = []ir.Node{index}
+		}
+		// This is a generic function instantiation (e.g. min[int])
+		x := g.expr(expr.X)
+		if x.Op() != ir.ONAME || x.Type().Kind() != types.TFUNC {
+			panic("Incorrect argument for generic func instantiation")
+		}
+		// This could also be an OTYPEINST once we can handle those examples.
+		n := ir.NewInstExpr(pos, ir.OFUNCINST, x, targs)
+		typed(g.typ(typ), n)
+		return n
+
+	case *syntax.ParenExpr:
+		return g.expr(expr.X) // skip parens; unneeded after parse+typecheck
+
+	case *syntax.SelectorExpr:
+		// Qualified identifier.
+		if name, ok := expr.X.(*syntax.Name); ok {
+			if _, ok := g.info.Uses[name].(*types2.PkgName); ok {
+				// TODO(mdempsky): Remove dependency on typecheck.Expr.
+				return typecheck.Expr(g.use(expr.Sel))
+			}
+		}
+		return g.selectorExpr(pos, typ, expr)
+
+	case *syntax.SliceExpr:
+		return Slice(pos, g.expr(expr.X), g.expr(expr.Index[0]), g.expr(expr.Index[1]), g.expr(expr.Index[2]))
+
+	case *syntax.Operation:
+		if expr.Y == nil {
+			return Unary(pos, g.op(expr.Op, unOps[:]), g.expr(expr.X))
+		}
+		switch op := g.op(expr.Op, binOps[:]); op {
+		case ir.OEQ, ir.ONE, ir.OLT, ir.OLE, ir.OGT, ir.OGE:
+			return Compare(pos, g.typ(typ), op, g.expr(expr.X), g.expr(expr.Y))
+		default:
+			return Binary(pos, op, g.expr(expr.X), g.expr(expr.Y))
+		}
+
+	default:
+		g.unhandled("expression", expr)
+		panic("unreachable")
+	}
+}
+
+// selectorExpr resolves the choice of ODOT, ODOTPTR, OCALLPART (eventually
+// ODOTMETH & ODOTINTER), and OMETHEXPR and deals with embedded fields here rather
+// than in typecheck.go.
+func (g *irgen) selectorExpr(pos src.XPos, typ types2.Type, expr *syntax.SelectorExpr) ir.Node {
+	x := g.expr(expr.X)
+	if x.Type().Kind() == types.TTYPEPARAM {
+		// Leave a method call on a type param as an OXDOT, since it can
+		// only be fully transformed once it has an instantiated type.
+		n := ir.NewSelectorExpr(pos, ir.OXDOT, x, typecheck.Lookup(expr.Sel.Value))
+		typed(g.typ(typ), n)
+		return n
+	}
+
+	selinfo := g.info.Selections[expr]
+	// Everything up to the last selection is an implicit embedded field access,
+	// and the last selection is determined by selinfo.Kind().
+	index := selinfo.Index()
+	embeds, last := index[:len(index)-1], index[len(index)-1]
+
+	origx := x
+	for _, ix := range embeds {
+		x = Implicit(DotField(pos, x, ix))
+	}
+
+	kind := selinfo.Kind()
+	if kind == types2.FieldVal {
+		return DotField(pos, x, last)
+	}
+
+	// TODO(danscales,mdempsky): Interface method sets are not sorted the
+	// same between types and types2. In particular, using "last" here
+	// without conversion will likely fail if an interface contains
+	// unexported methods from two different packages (due to cross-package
+	// interface embedding).
+
+	var n ir.Node
+	method2 := selinfo.Obj().(*types2.Func)
+
+	if kind == types2.MethodExpr {
+		// OMETHEXPR is unusual in using directly the node and type of the
+		// original OTYPE node (origx) before passing through embedded
+		// fields, even though the method is selected from the type
+		// (x.Type()) reached after following the embedded fields. We will
+		// actually drop any ODOT nodes we created due to the embedded
+		// fields.
+		n = MethodExpr(pos, origx, x.Type(), last)
+	} else {
+		// Add implicit addr/deref for method values, if needed.
+		if x.Type().IsInterface() {
+			n = DotMethod(pos, x, last)
+		} else {
+			recvType2 := method2.Type().(*types2.Signature).Recv().Type()
+			_, wantPtr := recvType2.(*types2.Pointer)
+			havePtr := x.Type().IsPtr()
+
+			if havePtr != wantPtr {
+				if havePtr {
+					x = Implicit(Deref(pos, x))
+				} else {
+					x = Implicit(Addr(pos, x))
+				}
+			}
+			recvType2Base := recvType2
+			if wantPtr {
+				recvType2Base = types2.AsPointer(recvType2).Elem()
+			}
+			if len(types2.AsNamed(recvType2Base).TParams()) > 0 {
+				// recvType2 is the original generic type that is
+				// instantiated for this method call.
+				// selinfo.Recv() is the instantiated type
+				recvType2 = recvType2Base
+				// method is the generic method associated with the gen type
+				method := g.obj(types2.AsNamed(recvType2).Method(last))
+				n = ir.NewSelectorExpr(pos, ir.OCALLPART, x, method.Sym())
+				n.(*ir.SelectorExpr).Selection = types.NewField(pos, method.Sym(), method.Type())
+				n.(*ir.SelectorExpr).Selection.Nname = method
+				typed(method.Type(), n)
+
+				// selinfo.Targs() are the types used to
+				// instantiate the type of receiver
+				targs2 := selinfo.TArgs()
+				targs := make([]ir.Node, len(targs2))
+				for i, targ2 := range targs2 {
+					targs[i] = ir.TypeNode(g.typ(targ2))
+				}
+
+				// Create function instantiation with the type
+				// args for the receiver type for the method call.
+				n = ir.NewInstExpr(pos, ir.OFUNCINST, n, targs)
+				typed(g.typ(typ), n)
+				return n
+			}
+
+			if !g.match(x.Type(), recvType2, false) {
+				base.FatalfAt(pos, "expected %L to have type %v", x, recvType2)
+			} else {
+				n = DotMethod(pos, x, last)
+			}
+		}
+	}
+	if have, want := n.Sym(), g.selector(method2); have != want {
+		base.FatalfAt(pos, "bad Sym: have %v, want %v", have, want)
+	}
+	return n
+}
+
+func (g *irgen) exprList(expr syntax.Expr) []ir.Node {
+	switch expr := expr.(type) {
+	case nil:
+		return nil
+	case *syntax.ListExpr:
+		return g.exprs(expr.ElemList)
+	default:
+		return []ir.Node{g.expr(expr)}
+	}
+}
+
+func (g *irgen) exprs(exprs []syntax.Expr) []ir.Node {
+	nodes := make([]ir.Node, len(exprs))
+	for i, expr := range exprs {
+		nodes[i] = g.expr(expr)
+	}
+	return nodes
+}
+
+func (g *irgen) compLit(typ types2.Type, lit *syntax.CompositeLit) ir.Node {
+	if ptr, ok := typ.Underlying().(*types2.Pointer); ok {
+		n := ir.NewAddrExpr(g.pos(lit), g.compLit(ptr.Elem(), lit))
+		n.SetOp(ir.OPTRLIT)
+		return typed(g.typ(typ), n)
+	}
+
+	_, isStruct := typ.Underlying().(*types2.Struct)
+
+	exprs := make([]ir.Node, len(lit.ElemList))
+	for i, elem := range lit.ElemList {
+		switch elem := elem.(type) {
+		case *syntax.KeyValueExpr:
+			if isStruct {
+				exprs[i] = ir.NewStructKeyExpr(g.pos(elem), g.name(elem.Key.(*syntax.Name)), g.expr(elem.Value))
+			} else {
+				exprs[i] = ir.NewKeyExpr(g.pos(elem), g.expr(elem.Key), g.expr(elem.Value))
+			}
+		default:
+			exprs[i] = g.expr(elem)
+		}
+	}
+
+	// TODO(mdempsky): Remove dependency on typecheck.Expr.
+	return typecheck.Expr(ir.NewCompLitExpr(g.pos(lit), ir.OCOMPLIT, ir.TypeNode(g.typ(typ)), exprs))
+}
+
+func (g *irgen) funcLit(typ2 types2.Type, expr *syntax.FuncLit) ir.Node {
+	fn := ir.NewFunc(g.pos(expr))
+	fn.SetIsHiddenClosure(ir.CurFunc != nil)
+
+	fn.Nname = ir.NewNameAt(g.pos(expr), typecheck.ClosureName(ir.CurFunc))
+	ir.MarkFunc(fn.Nname)
+	typ := g.typ(typ2)
+	fn.Nname.Func = fn
+	fn.Nname.Defn = fn
+	// Set Ntype for now to be compatible with later parts of compile, remove later.
+	fn.Nname.Ntype = ir.TypeNode(typ)
+	typed(typ, fn.Nname)
+	fn.SetTypecheck(1)
+
+	fn.OClosure = ir.NewClosureExpr(g.pos(expr), fn)
+	typed(typ, fn.OClosure)
+
+	g.funcBody(fn, nil, expr.Type, expr.Body)
+
+	ir.FinishCaptureNames(fn.Pos(), ir.CurFunc, fn)
+
+	// TODO(mdempsky): ir.CaptureName should probably handle
+	// copying these fields from the canonical variable.
+	for _, cv := range fn.ClosureVars {
+		cv.SetType(cv.Canonical().Type())
+		cv.SetTypecheck(1)
+		cv.SetWalkdef(1)
+	}
+
+	g.target.Decls = append(g.target.Decls, fn)
+
+	return fn.OClosure
+}
+
+func (g *irgen) typeExpr(typ syntax.Expr) *types.Type {
+	n := g.expr(typ)
+	if n.Op() != ir.OTYPE {
+		base.FatalfAt(g.pos(typ), "expected type: %L", n)
+	}
+	return n.Type()
+}

src/cmd/compile/internal/noder/func.go

@@ -0,0 +1,74 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package noder
+
+import (
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/syntax"
+	"cmd/compile/internal/typecheck"
+	"cmd/compile/internal/types"
+	"cmd/internal/src"
+)
+
+func (g *irgen) funcBody(fn *ir.Func, recv *syntax.Field, sig *syntax.FuncType, block *syntax.BlockStmt) {
+	typecheck.Func(fn)
+
+	// TODO(mdempsky): Remove uses of ir.CurFunc and
+	// typecheck.DeclContext after we stop relying on typecheck
+	// for desugaring.
+	outerfn, outerctxt := ir.CurFunc, typecheck.DeclContext
+	ir.CurFunc = fn
+
+	typ := fn.Type()
+	if param := typ.Recv(); param != nil {
+		g.defParam(param, recv, ir.PPARAM)
+	}
+	for i, param := range typ.Params().FieldSlice() {
+		g.defParam(param, sig.ParamList[i], ir.PPARAM)
+	}
+	for i, result := range typ.Results().FieldSlice() {
+		g.defParam(result, sig.ResultList[i], ir.PPARAMOUT)
+	}
+
+	// We may have type-checked a call to this function already and
+	// calculated its size, including parameter offsets. Now that we've
+	// created the parameter Names, force a recalculation to ensure
+	// their offsets are correct.
+	typ.Align = 0
+	types.CalcSize(typ)
+
+	if block != nil {
+		typecheck.DeclContext = ir.PAUTO
+
+		fn.Body = g.stmts(block.List)
+		if fn.Body == nil {
+			fn.Body = []ir.Node{ir.NewBlockStmt(src.NoXPos, nil)}
+		}
+		fn.Endlineno = g.makeXPos(block.Rbrace)
+
+		if base.Flag.Dwarf {
+			g.recordScopes(fn, sig)
+		}
+	}
+
+	ir.CurFunc, typecheck.DeclContext = outerfn, outerctxt
+}
+
+func (g *irgen) defParam(param *types.Field, decl *syntax.Field, class ir.Class) {
+	typecheck.DeclContext = class
+
+	var name *ir.Name
+	if decl.Name != nil {
+		name, _ = g.def(decl.Name)
+	} else if class == ir.PPARAMOUT {
+		name = g.obj(g.info.Implicits[decl])
+	}
+
+	if name != nil {
+		param.Nname = name
+		param.Sym = name.Sym() // in case it was renamed
+	}
+}

src/cmd/compile/internal/noder/helpers.go

@@ -0,0 +1,277 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package noder
+
+import (
+	"go/constant"
+
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/typecheck"
+	"cmd/compile/internal/types"
+	"cmd/internal/src"
+)
+
+// Helpers for constructing typed IR nodes.
+//
+// TODO(mdempsky): Move into their own package so they can be easily
+// reused by iimport and frontend optimizations.
+//
+// TODO(mdempsky): Update to consistently return already typechecked
+// results, rather than leaving the caller responsible for using
+// typecheck.Expr or typecheck.Stmt.
+
+type ImplicitNode interface {
+	ir.Node
+	SetImplicit(x bool)
+}
+
+// Implicit returns n after marking it as Implicit.
+func Implicit(n ImplicitNode) ImplicitNode {
+	n.SetImplicit(true)
+	return n
+}
+
+// typed returns n after setting its type to typ.
+func typed(typ *types.Type, n ir.Node) ir.Node {
+	n.SetType(typ)
+	n.SetTypecheck(1)
+	return n
+}
+
+// Values
+
+func Const(pos src.XPos, typ *types.Type, val constant.Value) ir.Node {
+	return typed(typ, ir.NewBasicLit(pos, val))
+}
+
+func Nil(pos src.XPos, typ *types.Type) ir.Node {
+	return typed(typ, ir.NewNilExpr(pos))
+}
+
+// Expressions
+
+func Addr(pos src.XPos, x ir.Node) *ir.AddrExpr {
+	// TODO(mdempsky): Avoid typecheck.Expr. Probably just need to set OPTRLIT when appropriate.
+	n := typecheck.Expr(typecheck.NodAddrAt(pos, x)).(*ir.AddrExpr)
+	typed(types.NewPtr(x.Type()), n)
+	return n
+}
+
+func Assert(pos src.XPos, x ir.Node, typ *types.Type) ir.Node {
+	return typed(typ, ir.NewTypeAssertExpr(pos, x, nil))
+}
+
+func Binary(pos src.XPos, op ir.Op, x, y ir.Node) ir.Node {
+	switch op {
+	case ir.OANDAND, ir.OOROR:
+		return typed(x.Type(), ir.NewLogicalExpr(pos, op, x, y))
+	case ir.OADD:
+		if x.Type().IsString() {
+			// TODO(mdempsky): Construct OADDSTR directly.
+			return typecheck.Expr(ir.NewBinaryExpr(pos, op, x, y))
+		}
+		fallthrough
+	default:
+		return typed(x.Type(), ir.NewBinaryExpr(pos, op, x, y))
+	}
+}
+
+func Call(pos src.XPos, typ *types.Type, fun ir.Node, args []ir.Node, dots bool) ir.Node {
+	// TODO(mdempsky): This should not be so difficult.
+	if fun.Op() == ir.OTYPE {
+		// Actually a type conversion, not a function call.
+		n := ir.NewCallExpr(pos, ir.OCALL, fun, args)
+		if fun.Type().Kind() == types.TTYPEPARAM {
+			// For type params, don't typecheck until we actually know
+			// the type.
+			return typed(typ, n)
+		}
+		return typecheck.Expr(n)
+	}
+
+	if fun, ok := fun.(*ir.Name); ok && fun.BuiltinOp != 0 {
+		// Call to a builtin function.
+		n := ir.NewCallExpr(pos, ir.OCALL, fun, args)
+		n.IsDDD = dots
+		switch fun.BuiltinOp {
+		case ir.OCLOSE, ir.ODELETE, ir.OPANIC, ir.OPRINT, ir.OPRINTN:
+			return typecheck.Stmt(n)
+		default:
+			return typecheck.Expr(n)
+		}
+	}
+
+	// Add information, now that we know that fun is actually being called.
+	switch fun := fun.(type) {
+	case *ir.ClosureExpr:
+		fun.Func.SetClosureCalled(true)
+	case *ir.SelectorExpr:
+		if fun.Op() == ir.OCALLPART {
+			op := ir.ODOTMETH
+			if fun.X.Type().IsInterface() {
+				op = ir.ODOTINTER
+			}
+			fun.SetOp(op)
+			// Set the type to include the receiver, since that's what
+			// later parts of the compiler expect
+			fun.SetType(fun.Selection.Type)
+		}
+	}
+
+	n := ir.NewCallExpr(pos, ir.OCALL, fun, args)
+	n.IsDDD = dots
+
+	if fun.Op() == ir.OXDOT {
+		if fun.(*ir.SelectorExpr).X.Type().Kind() != types.TTYPEPARAM {
+			base.FatalfAt(pos, "Expecting type param receiver in %v", fun)
+		}
+		// For methods called in a generic function, don't do any extra
+		// transformations. We will do those later when we create the
+		// instantiated function and have the correct receiver type.
+		typed(typ, n)
+		return n
+	}
+	if fun.Op() != ir.OFUNCINST {
+		// If no type params, still do normal typechecking, since we're
+		// still missing some things done by tcCall below (mainly
+		// typecheckargs and typecheckaste).
+		typecheck.Call(n)
+		return n
+	}
+
+	n.Use = ir.CallUseExpr
+	if fun.Type().NumResults() == 0 {
+		n.Use = ir.CallUseStmt
+	}
+
+	// Rewrite call node depending on use.
+	switch fun.Op() {
+	case ir.ODOTINTER:
+		n.SetOp(ir.OCALLINTER)
+
+	case ir.ODOTMETH:
+		n.SetOp(ir.OCALLMETH)
+
+	default:
+		n.SetOp(ir.OCALLFUNC)
+	}
+
+	typed(typ, n)
+	return n
+}
+
+func Compare(pos src.XPos, typ *types.Type, op ir.Op, x, y ir.Node) ir.Node {
+	n := ir.NewBinaryExpr(pos, op, x, y)
+	if !types.Identical(x.Type(), y.Type()) {
+		// TODO(mdempsky): Handle subtleties of constructing mixed-typed comparisons.
+		n = typecheck.Expr(n).(*ir.BinaryExpr)
+	}
+	return typed(typ, n)
+}
+
+func Deref(pos src.XPos, x ir.Node) *ir.StarExpr {
+	n := ir.NewStarExpr(pos, x)
+	typed(x.Type().Elem(), n)
+	return n
+}
+
+func DotField(pos src.XPos, x ir.Node, index int) *ir.SelectorExpr {
+	op, typ := ir.ODOT, x.Type()
+	if typ.IsPtr() {
+		op, typ = ir.ODOTPTR, typ.Elem()
+	}
+	if !typ.IsStruct() {
+		base.FatalfAt(pos, "DotField of non-struct: %L", x)
+	}
+
+	// TODO(mdempsky): This is the backend's responsibility.
+	types.CalcSize(typ)
+
+	field := typ.Field(index)
+	return dot(pos, field.Type, op, x, field)
+}
+
+func DotMethod(pos src.XPos, x ir.Node, index int) *ir.SelectorExpr {
+	method := method(x.Type(), index)
+
+	// Method value.
+	typ := typecheck.NewMethodType(method.Type, nil)
+	return dot(pos, typ, ir.OCALLPART, x, method)
+}
+
+// MethodExpr returns a OMETHEXPR node with the indicated index into the methods
+// of typ. The receiver type is set from recv, which is different from typ if the
+// method was accessed via embedded fields. Similarly, the X value of the
+// ir.SelectorExpr is recv, the original OTYPE node before passing through the
+// embedded fields.
+func MethodExpr(pos src.XPos, recv ir.Node, embed *types.Type, index int) *ir.SelectorExpr {
+	method := method(embed, index)
+	typ := typecheck.NewMethodType(method.Type, recv.Type())
+	// The method expression T.m requires a wrapper when T
+	// is different from m's declared receiver type. We
+	// normally generate these wrappers while writing out
+	// runtime type descriptors, which is always done for
+	// types declared at package scope. However, we need
+	// to make sure to generate wrappers for anonymous
+	// receiver types too.
+	if recv.Sym() == nil {
+		typecheck.NeedRuntimeType(recv.Type())
+	}
+	return dot(pos, typ, ir.OMETHEXPR, recv, method)
+}
+
+func dot(pos src.XPos, typ *types.Type, op ir.Op, x ir.Node, selection *types.Field) *ir.SelectorExpr {
+	n := ir.NewSelectorExpr(pos, op, x, selection.Sym)
+	n.Selection = selection
+	typed(typ, n)
+	return n
+}
+
+// TODO(mdempsky): Move to package types.
+func method(typ *types.Type, index int) *types.Field {
+	if typ.IsInterface() {
+		return typ.Field(index)
+	}
+	return types.ReceiverBaseType(typ).Methods().Index(index)
+}
+
+func Index(pos src.XPos, x, index ir.Node) ir.Node {
+	// TODO(mdempsky): Avoid typecheck.Expr (which will call tcIndex)
+	return typecheck.Expr(ir.NewIndexExpr(pos, x, index))
+}
+
+func Slice(pos src.XPos, x, low, high, max ir.Node) ir.Node {
+	op := ir.OSLICE
+	if max != nil {
+		op = ir.OSLICE3
+	}
+	// TODO(mdempsky): Avoid typecheck.Expr.
+	return typecheck.Expr(ir.NewSliceExpr(pos, op, x, low, high, max))
+}
+
+func Unary(pos src.XPos, op ir.Op, x ir.Node) ir.Node {
+	switch op {
+	case ir.OADDR:
+		return Addr(pos, x)
+	case ir.ODEREF:
+		return Deref(pos, x)
+	}
+
+	typ := x.Type()
+	if op == ir.ORECV {
+		typ = typ.Elem()
+	}
+	return typed(typ, ir.NewUnaryExpr(pos, op, x))
+}
+
+// Statements
+
+var one = constant.MakeInt64(1)
+
+func IncDec(pos src.XPos, op ir.Op, x ir.Node) ir.Node {
+	x = typecheck.AssignExpr(x)
+	return ir.NewAssignOpStmt(pos, op, x, typecheck.DefaultLit(ir.NewBasicLit(pos, one), x.Type()))
+}

src/cmd/compile/internal/noder/import.go

@@ -7,6 +7,7 @@ package noder
 import (
 	"errors"
 	"fmt"
+	"io"
 	"os"
 	pathpkg "path"
 	"runtime"
@@ -17,10 +18,12 @@ import (
 	"unicode/utf8"
 
 	"cmd/compile/internal/base"
+	"cmd/compile/internal/importer"
 	"cmd/compile/internal/ir"
 	"cmd/compile/internal/syntax"
 	"cmd/compile/internal/typecheck"
 	"cmd/compile/internal/types"
+	"cmd/compile/internal/types2"
 	"cmd/internal/archive"
 	"cmd/internal/bio"
 	"cmd/internal/goobj"
@@ -28,6 +31,29 @@ import (
 	"cmd/internal/src"
 )
 
+// Temporary import helper to get type2-based type-checking going.
+type gcimports struct {
+	packages map[string]*types2.Package
+}
+
+func (m *gcimports) Import(path string) (*types2.Package, error) {
+	return m.ImportFrom(path, "" /* no vendoring */, 0)
+}
+
+func (m *gcimports) ImportFrom(path, srcDir string, mode types2.ImportMode) (*types2.Package, error) {
+	if mode != 0 {
+		panic("mode must be 0")
+	}
+
+	path, err := resolveImportPath(path)
+	if err != nil {
+		return nil, err
+	}
+
+	lookup := func(path string) (io.ReadCloser, error) { return openPackage(path) }
+	return importer.Import(m.packages, path, srcDir, lookup)
+}
+
 func isDriveLetter(b byte) bool {
 	return 'a' <= b && b <= 'z' || 'A' <= b && b <= 'Z'
 }

src/cmd/compile/internal/noder/irgen.go

@@ -0,0 +1,209 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package noder
+
+import (
+	"fmt"
+	"os"
+
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/dwarfgen"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/syntax"
+	"cmd/compile/internal/typecheck"
+	"cmd/compile/internal/types"
+	"cmd/compile/internal/types2"
+	"cmd/internal/src"
+)
+
+// check2 type checks a Go package using types2, and then generates IR
+// using the results.
+func check2(noders []*noder) {
+	if base.SyntaxErrors() != 0 {
+		base.ErrorExit()
+	}
+
+	// setup and syntax error reporting
+	var m posMap
+	files := make([]*syntax.File, len(noders))
+	for i, p := range noders {
+		m.join(&p.posMap)
+		files[i] = p.file
+	}
+
+	// typechecking
+	conf := types2.Config{
+		GoVersion:             base.Flag.Lang,
+		InferFromConstraints:  true,
+		IgnoreLabels:          true, // parser already checked via syntax.CheckBranches mode
+		CompilerErrorMessages: true, // use error strings matching existing compiler errors
+		Error: func(err error) {
+			terr := err.(types2.Error)
+			if len(terr.Msg) > 0 && terr.Msg[0] == '\t' {
+				// types2 reports error clarifications via separate
+				// error messages which are indented with a tab.
+				// Ignore them to satisfy tools and tests that expect
+				// only one error in such cases.
+				// TODO(gri) Need to adjust error reporting in types2.
+				return
+			}
+			base.ErrorfAt(m.makeXPos(terr.Pos), "%s", terr.Msg)
+		},
+		Importer: &gcimports{
+			packages: make(map[string]*types2.Package),
+		},
+		Sizes: &gcSizes{},
+	}
+	info := types2.Info{
+		Types:      make(map[syntax.Expr]types2.TypeAndValue),
+		Defs:       make(map[*syntax.Name]types2.Object),
+		Uses:       make(map[*syntax.Name]types2.Object),
+		Selections: make(map[*syntax.SelectorExpr]*types2.Selection),
+		Implicits:  make(map[syntax.Node]types2.Object),
+		Scopes:     make(map[syntax.Node]*types2.Scope),
+		Inferred:   make(map[syntax.Expr]types2.Inferred),
+		// expand as needed
+	}
+	pkg, err := conf.Check(base.Ctxt.Pkgpath, files, &info)
+	files = nil
+	if err != nil {
+		base.FatalfAt(src.NoXPos, "conf.Check error: %v", err)
+	}
+	base.ExitIfErrors()
+	if base.Flag.G < 2 {
+		os.Exit(0)
+	}
+
+	g := irgen{
+		target: typecheck.Target,
+		self:   pkg,
+		info:   &info,
+		posMap: m,
+		objs:   make(map[types2.Object]*ir.Name),
+		typs:   make(map[types2.Type]*types.Type),
+	}
+	g.generate(noders)
+
+	if base.Flag.G < 3 {
+		os.Exit(0)
+	}
+}
+
+type irgen struct {
+	target *ir.Package
+	self   *types2.Package
+	info   *types2.Info
+
+	posMap
+	objs   map[types2.Object]*ir.Name
+	typs   map[types2.Type]*types.Type
+	marker dwarfgen.ScopeMarker
+}
+
+func (g *irgen) generate(noders []*noder) {
+	types.LocalPkg.Name = g.self.Name()
+	typecheck.TypecheckAllowed = true
+
+	// Prevent size calculations until we set the underlying type
+	// for all package-block defined types.
+	types.DeferCheckSize()
+
+	// At this point, types2 has already handled name resolution and
+	// type checking. We just need to map from its object and type
+	// representations to those currently used by the rest of the
+	// compiler. This happens mostly in 3 passes.
+
+	// 1. Process all import declarations. We use the compiler's own
+	// importer for this, rather than types2's gcimporter-derived one,
+	// to handle extensions and inline function bodies correctly.
+	//
+	// Also, we need to do this in a separate pass, because mappings are
+	// instantiated on demand. If we interleaved processing import
+	// declarations with other declarations, it's likely we'd end up
+	// wanting to map an object/type from another source file, but not
+	// yet have the import data it relies on.
+	declLists := make([][]syntax.Decl, len(noders))
+Outer:
+	for i, p := range noders {
+		g.pragmaFlags(p.file.Pragma, ir.GoBuildPragma)
+		for j, decl := range p.file.DeclList {
+			switch decl := decl.(type) {
+			case *syntax.ImportDecl:
+				g.importDecl(p, decl)
+			default:
+				declLists[i] = p.file.DeclList[j:]
+				continue Outer // no more ImportDecls
+			}
+		}
+	}
+	types.LocalPkg.Height = myheight
+
+	// 2. Process all package-block type declarations. As with imports,
+	// we need to make sure all types are properly instantiated before
+	// trying to map any expressions that utilize them. In particular,
+	// we need to make sure type pragmas are already known (see comment
+	// in irgen.typeDecl).
+	//
+	// We could perhaps instead defer processing of package-block
+	// variable initializers and function bodies, like noder does, but
+	// special-casing just package-block type declarations minimizes the
+	// differences between processing package-block and function-scoped
+	// declarations.
+	for _, declList := range declLists {
+		for _, decl := range declList {
+			switch decl := decl.(type) {
+			case *syntax.TypeDecl:
+				g.typeDecl((*ir.Nodes)(&g.target.Decls), decl)
+			}
+		}
+	}
+	types.ResumeCheckSize()
+
+	// 3. Process all remaining declarations.
+	for _, declList := range declLists {
+		g.target.Decls = append(g.target.Decls, g.decls(declList)...)
+	}
+
+	if base.Flag.W > 1 {
+		for _, n := range g.target.Decls {
+			s := fmt.Sprintf("\nafter noder2 %v", n)
+			ir.Dump(s, n)
+		}
+	}
+
+	typecheck.DeclareUniverse()
+
+	for _, p := range noders {
+		// Process linkname and cgo pragmas.
+		p.processPragmas()
+
+		// Double check for any type-checking inconsistencies. This can be
+		// removed once we're confident in IR generation results.
+		syntax.Walk(p.file, func(n syntax.Node) bool {
+			g.validate(n)
+			return false
+		})
+	}
+
+	// Create any needed stencils of generic functions
+	g.stencil()
+
+	// For now, remove all generic functions from g.target.Decl, since they
+	// have been used for stenciling, but don't compile. TODO: We will
+	// eventually export any exportable generic functions.
+	j := 0
+	for i, decl := range g.target.Decls {
+		if decl.Op() != ir.ODCLFUNC || !decl.Type().HasTParam() {
+			g.target.Decls[j] = g.target.Decls[i]
+			j++
+		}
+	}
+	g.target.Decls = g.target.Decls[:j]
+}
+
+func (g *irgen) unhandled(what string, p poser) {
+	base.FatalfAt(g.pos(p), "unhandled %s: %T", what, p)
+	panic("unreachable")
+}

src/cmd/compile/internal/noder/lex.go

@@ -28,7 +28,7 @@ const (
 		ir.Nosplit |
 		ir.Noinline |
 		ir.NoCheckPtr |
-		ir.RegisterParams | // TODO remove after register abi is working
+		ir.RegisterParams | // TODO(register args) remove after register abi is working
 		ir.CgoUnsafeArgs |
 		ir.UintptrEscapes |
 		ir.Systemstack |
@@ -80,7 +80,7 @@ func pragmaFlag(verb string) ir.PragmaFlag {
 		// in the argument list.
 		// Used in syscall/dll_windows.go.
 		return ir.UintptrEscapes
-	case "go:registerparams": // TODO remove after register abi is working
+	case "go:registerparams": // TODO(register args) remove after register abi is working
 		return ir.RegisterParams
 	case "go:notinheap":
 		return ir.NotInHeap

src/cmd/compile/internal/noder/noder.go

@@ -30,6 +30,9 @@ func LoadPackage(filenames []string) {
 	base.Timer.Start("fe", "parse")
 
 	mode := syntax.CheckBranches
+	if base.Flag.G != 0 {
+		mode |= syntax.AllowGenerics
+	}
 
 	// Limit the number of simultaneously open files.
 	sem := make(chan struct{}, runtime.GOMAXPROCS(0)+10)
@@ -65,10 +68,16 @@ func LoadPackage(filenames []string) {
 		for e := range p.err {
 			p.errorAt(e.Pos, "%s", e.Msg)
 		}
-		lines += p.file.Lines
+		lines += p.file.EOF.Line()
 	}
 	base.Timer.AddEvent(int64(lines), "lines")
 
+	if base.Flag.G != 0 {
+		// Use types2 to type-check and possibly generate IR.
+		check2(noders)
+		return
+	}
+
 	for _, p := range noders {
 		p.node()
 		p.file = nil // release memory
@@ -1031,8 +1040,7 @@ func (p *noder) stmtFall(stmt syntax.Stmt, fallOK bool) ir.Node {
 	case *syntax.DeclStmt:
 		return ir.NewBlockStmt(src.NoXPos, p.decls(stmt.DeclList))
 	case *syntax.AssignStmt:
-		if stmt.Rhs == syntax.ImplicitOne {
-			one := constant.MakeInt64(1)
+		if stmt.Rhs == nil {
 			pos := p.pos(stmt)
 			n := ir.NewAssignOpStmt(pos, p.binOp(stmt.Op), p.expr(stmt.Lhs), ir.NewBasicLit(pos, one))
 			n.IncDec = true
@@ -1447,6 +1455,20 @@ func (p *noder) basicLit(lit *syntax.BasicLit) constant.Value {
 	switch lit.Kind {
 	case syntax.IntLit, syntax.FloatLit, syntax.ImagLit:
 		checkLangCompat(lit)
+		// The max. mantissa precision for untyped numeric values
+		// is 512 bits, or 4048 bits for each of the two integer
+		// parts of a fraction for floating-point numbers that are
+		// represented accurately in the go/constant package.
+		// Constant literals that are longer than this many bits
+		// are not meaningful; and excessively long constants may
+		// consume a lot of space and time for a useless conversion.
+		// Cap constant length with a generous upper limit that also
+		// allows for separators between all digits.
+		const limit = 10000
+		if len(lit.Value) > limit {
+			p.errorAt(lit.Pos(), "excessively long constant: %s... (%d chars)", lit.Value[:10], len(lit.Value))
+			return constant.MakeUnknown()
+		}
 	}
 
 	v := constant.MakeFromLiteral(lit.Value, tokenForLitKind[lit.Kind], 0)

src/cmd/compile/internal/noder/object.go

@@ -0,0 +1,175 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package noder
+
+import (
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/syntax"
+	"cmd/compile/internal/typecheck"
+	"cmd/compile/internal/types"
+	"cmd/compile/internal/types2"
+	"cmd/internal/src"
+)
+
+func (g *irgen) def(name *syntax.Name) (*ir.Name, types2.Object) {
+	obj, ok := g.info.Defs[name]
+	if !ok {
+		base.FatalfAt(g.pos(name), "unknown name %v", name)
+	}
+	return g.obj(obj), obj
+}
+
+func (g *irgen) use(name *syntax.Name) *ir.Name {
+	obj, ok := g.info.Uses[name]
+	if !ok {
+		base.FatalfAt(g.pos(name), "unknown name %v", name)
+	}
+	return ir.CaptureName(g.pos(obj), ir.CurFunc, g.obj(obj))
+}
+
+// obj returns the Name that represents the given object. If no such
+// Name exists yet, it will be implicitly created.
+//
+// For objects declared at function scope, ir.CurFunc must already be
+// set to the respective function when the Name is created.
+func (g *irgen) obj(obj types2.Object) *ir.Name {
+	// For imported objects, we use iimport directly instead of mapping
+	// the types2 representation.
+	if obj.Pkg() != g.self {
+		sym := g.sym(obj)
+		if sym.Def != nil {
+			return sym.Def.(*ir.Name)
+		}
+		n := typecheck.Resolve(ir.NewIdent(src.NoXPos, sym))
+		if n, ok := n.(*ir.Name); ok {
+			return n
+		}
+		base.FatalfAt(g.pos(obj), "failed to resolve %v", obj)
+	}
+
+	if name, ok := g.objs[obj]; ok {
+		return name // previously mapped
+	}
+
+	var name *ir.Name
+	pos := g.pos(obj)
+
+	class := typecheck.DeclContext
+	if obj.Parent() == g.self.Scope() {
+		class = ir.PEXTERN // forward reference to package-block declaration
+	}
+
+	// "You are in a maze of twisting little passages, all different."
+	switch obj := obj.(type) {
+	case *types2.Const:
+		name = g.objCommon(pos, ir.OLITERAL, g.sym(obj), class, g.typ(obj.Type()))
+
+	case *types2.Func:
+		sig := obj.Type().(*types2.Signature)
+		var sym *types.Sym
+		var typ *types.Type
+		if recv := sig.Recv(); recv == nil {
+			if obj.Name() == "init" {
+				sym = renameinit()
+			} else {
+				sym = g.sym(obj)
+			}
+			typ = g.typ(sig)
+		} else {
+			sym = g.selector(obj)
+			if !sym.IsBlank() {
+				sym = ir.MethodSym(g.typ(recv.Type()), sym)
+			}
+			typ = g.signature(g.param(recv), sig)
+		}
+		name = g.objCommon(pos, ir.ONAME, sym, ir.PFUNC, typ)
+
+	case *types2.TypeName:
+		if obj.IsAlias() {
+			name = g.objCommon(pos, ir.OTYPE, g.sym(obj), class, g.typ(obj.Type()))
+		} else {
+			name = ir.NewDeclNameAt(pos, ir.OTYPE, g.sym(obj))
+			g.objFinish(name, class, types.NewNamed(name))
+		}
+
+	case *types2.Var:
+		var sym *types.Sym
+		if class == ir.PPARAMOUT {
+			// Backend needs names for result parameters,
+			// even if they're anonymous or blank.
+			switch obj.Name() {
+			case "":
+				sym = typecheck.LookupNum("~r", len(ir.CurFunc.Dcl)) // 'r' for "result"
+			case "_":
+				sym = typecheck.LookupNum("~b", len(ir.CurFunc.Dcl)) // 'b' for "blank"
+			}
+		}
+		if sym == nil {
+			sym = g.sym(obj)
+		}
+		name = g.objCommon(pos, ir.ONAME, sym, class, g.typ(obj.Type()))
+
+	default:
+		g.unhandled("object", obj)
+	}
+
+	g.objs[obj] = name
+	return name
+}
+
+func (g *irgen) objCommon(pos src.XPos, op ir.Op, sym *types.Sym, class ir.Class, typ *types.Type) *ir.Name {
+	name := ir.NewDeclNameAt(pos, op, sym)
+	g.objFinish(name, class, typ)
+	return name
+}
+
+func (g *irgen) objFinish(name *ir.Name, class ir.Class, typ *types.Type) {
+	sym := name.Sym()
+
+	name.SetType(typ)
+	name.Class = class
+	if name.Class == ir.PFUNC {
+		sym.SetFunc(true)
+	}
+
+	// We already know name's type, but typecheck is really eager to try
+	// recomputing it later. This appears to prevent that at least.
+	name.Ntype = ir.TypeNode(typ)
+	name.SetTypecheck(1)
+	name.SetWalkdef(1)
+
+	if ir.IsBlank(name) {
+		return
+	}
+
+	switch class {
+	case ir.PEXTERN:
+		g.target.Externs = append(g.target.Externs, name)
+		fallthrough
+	case ir.PFUNC:
+		sym.Def = name
+		if name.Class == ir.PFUNC && name.Type().Recv() != nil {
+			break // methods are exported with their receiver type
+		}
+		if types.IsExported(sym.Name) {
+			if name.Class == ir.PFUNC && name.Type().NumTParams() > 0 {
+				base.FatalfAt(name.Pos(), "Cannot export a generic function (yet): %v", name)
+			}
+			typecheck.Export(name)
+		}
+		if base.Flag.AsmHdr != "" && !name.Sym().Asm() {
+			name.Sym().SetAsm(true)
+			g.target.Asms = append(g.target.Asms, name)
+		}
+
+	default:
+		// Function-scoped declaration.
+		name.Curfn = ir.CurFunc
+		if name.Op() == ir.ONAME {
+			ir.CurFunc.Dcl = append(ir.CurFunc.Dcl, name)
+		}
+	}
+}

src/cmd/compile/internal/noder/scopes.go

@@ -0,0 +1,64 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package noder
+
+import (
+	"strings"
+
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/syntax"
+	"cmd/compile/internal/types2"
+)
+
+// recordScopes populates fn.Parents and fn.Marks based on the scoping
+// information provided by types2.
+func (g *irgen) recordScopes(fn *ir.Func, sig *syntax.FuncType) {
+	scope, ok := g.info.Scopes[sig]
+	if !ok {
+		base.FatalfAt(fn.Pos(), "missing scope for %v", fn)
+	}
+
+	for i, n := 0, scope.NumChildren(); i < n; i++ {
+		g.walkScope(scope.Child(i))
+	}
+
+	g.marker.WriteTo(fn)
+}
+
+func (g *irgen) walkScope(scope *types2.Scope) bool {
+	// types2 doesn't provide a proper API for determining the
+	// lexical element a scope represents, so we have to resort to
+	// string matching. Conveniently though, this allows us to
+	// skip both function types and function literals, neither of
+	// which are interesting to us here.
+	if strings.HasPrefix(scope.String(), "function scope ") {
+		return false
+	}
+
+	g.marker.Push(g.pos(scope))
+
+	haveVars := false
+	for _, name := range scope.Names() {
+		if obj, ok := scope.Lookup(name).(*types2.Var); ok && obj.Name() != "_" {
+			haveVars = true
+			break
+		}
+	}
+
+	for i, n := 0, scope.NumChildren(); i < n; i++ {
+		if g.walkScope(scope.Child(i)) {
+			haveVars = true
+		}
+	}
+
+	if haveVars {
+		g.marker.Pop(g.end(scope))
+	} else {
+		g.marker.Unpush()
+	}
+
+	return haveVars
+}

src/cmd/compile/internal/noder/sizes.go

@@ -0,0 +1,150 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package noder
+
+import (
+	"fmt"
+
+	"cmd/compile/internal/types"
+	"cmd/compile/internal/types2"
+)
+
+// Code below based on go/types.StdSizes.
+// Intentional differences are marked with "gc:".
+
+type gcSizes struct{}
+
+func (s *gcSizes) Alignof(T types2.Type) int64 {
+	// For arrays and structs, alignment is defined in terms
+	// of alignment of the elements and fields, respectively.
+	switch t := T.Underlying().(type) {
+	case *types2.Array:
+		// spec: "For a variable x of array type: unsafe.Alignof(x)
+		// is the same as unsafe.Alignof(x[0]), but at least 1."
+		return s.Alignof(t.Elem())
+	case *types2.Struct:
+		// spec: "For a variable x of struct type: unsafe.Alignof(x)
+		// is the largest of the values unsafe.Alignof(x.f) for each
+		// field f of x, but at least 1."
+		max := int64(1)
+		for i, nf := 0, t.NumFields(); i < nf; i++ {
+			if a := s.Alignof(t.Field(i).Type()); a > max {
+				max = a
+			}
+		}
+		return max
+	case *types2.Slice, *types2.Interface:
+		// Multiword data structures are effectively structs
+		// in which each element has size PtrSize.
+		return int64(types.PtrSize)
+	case *types2.Basic:
+		// Strings are like slices and interfaces.
+		if t.Info()&types2.IsString != 0 {
+			return int64(types.PtrSize)
+		}
+	}
+	a := s.Sizeof(T) // may be 0
+	// spec: "For a variable x of any type: unsafe.Alignof(x) is at least 1."
+	if a < 1 {
+		return 1
+	}
+	// complex{64,128} are aligned like [2]float{32,64}.
+	if isComplex(T) {
+		a /= 2
+	}
+	if a > int64(types.RegSize) {
+		return int64(types.RegSize)
+	}
+	return a
+}
+
+func isComplex(T types2.Type) bool {
+	basic, ok := T.Underlying().(*types2.Basic)
+	return ok && basic.Info()&types2.IsComplex != 0
+}
+
+func (s *gcSizes) Offsetsof(fields []*types2.Var) []int64 {
+	offsets := make([]int64, len(fields))
+	var o int64
+	for i, f := range fields {
+		typ := f.Type()
+		a := s.Alignof(typ)
+		o = types.Rnd(o, a)
+		offsets[i] = o
+		o += s.Sizeof(typ)
+	}
+	return offsets
+}
+
+func (s *gcSizes) Sizeof(T types2.Type) int64 {
+	switch t := T.Underlying().(type) {
+	case *types2.Basic:
+		k := t.Kind()
+		if int(k) < len(basicSizes) {
+			if s := basicSizes[k]; s > 0 {
+				return int64(s)
+			}
+		}
+		switch k {
+		case types2.String:
+			return int64(types.PtrSize) * 2
+		case types2.Int, types2.Uint, types2.Uintptr, types2.UnsafePointer:
+			return int64(types.PtrSize)
+		}
+		panic(fmt.Sprintf("unimplemented basic: %v (kind %v)", T, k))
+	case *types2.Array:
+		n := t.Len()
+		if n <= 0 {
+			return 0
+		}
+		// n > 0
+		// gc: Size includes alignment padding.
+		return s.Sizeof(t.Elem()) * n
+	case *types2.Slice:
+		return int64(types.PtrSize) * 3
+	case *types2.Struct:
+		n := t.NumFields()
+		if n == 0 {
+			return 0
+		}
+		fields := make([]*types2.Var, n)
+		for i := range fields {
+			fields[i] = t.Field(i)
+		}
+		offsets := s.Offsetsof(fields)
+
+		// gc: The last field of a struct is not allowed to
+		// have size 0.
+		last := s.Sizeof(fields[n-1].Type())
+		if last == 0 {
+			last = 1
+		}
+
+		// gc: Size includes alignment padding.
+		return types.Rnd(offsets[n-1]+last, s.Alignof(t))
+	case *types2.Interface:
+		return int64(types.PtrSize) * 2
+	case *types2.Chan, *types2.Map, *types2.Pointer, *types2.Signature:
+		return int64(types.PtrSize)
+	default:
+		panic(fmt.Sprintf("unimplemented type: %T", t))
+	}
+}
+
+var basicSizes = [...]byte{
+	types2.Bool:       1,
+	types2.Int8:       1,
+	types2.Int16:      2,
+	types2.Int32:      4,
+	types2.Int64:      8,
+	types2.Uint8:      1,
+	types2.Uint16:     2,
+	types2.Uint32:     4,
+	types2.Uint64:     8,
+	types2.Float32:    4,
+	types2.Float64:    8,
+	types2.Complex64:  8,
+	types2.Complex128: 16,
+}

src/cmd/compile/internal/noder/stencil.go

@@ -0,0 +1,556 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file will evolve, since we plan to do a mix of stenciling and passing
+// around dictionaries.
+
+package noder
+
+import (
+	"bytes"
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/typecheck"
+	"cmd/compile/internal/types"
+	"cmd/internal/src"
+	"fmt"
+	"strings"
+)
+
+// stencil scans functions for instantiated generic function calls and
+// creates the required stencils for simple generic functions.
+func (g *irgen) stencil() {
+	g.target.Stencils = make(map[*types.Sym]*ir.Func)
+	// Don't use range(g.target.Decls) - we also want to process any new instantiated
+	// functions that are created during this loop, in order to handle generic
+	// functions calling other generic functions.
+	for i := 0; i < len(g.target.Decls); i++ {
+		decl := g.target.Decls[i]
+
+		// Look for function instantiations in bodies of non-generic
+		// functions or in global assignments (ignore global type and
+		// constant declarations).
+		switch decl.Op() {
+		case ir.ODCLFUNC:
+			if decl.Type().HasTParam() {
+				// Skip any generic functions
+				continue
+			}
+
+		case ir.OAS:
+
+		case ir.OAS2:
+
+		default:
+			continue
+		}
+
+		// For all non-generic code, search for any function calls using
+		// generic function instantiations. Then create the needed
+		// instantiated function if it hasn't been created yet, and change
+		// to calling that function directly.
+		modified := false
+		foundFuncInst := false
+		ir.Visit(decl, func(n ir.Node) {
+			if n.Op() == ir.OFUNCINST {
+				// We found a function instantiation that is not
+				// immediately called.
+				foundFuncInst = true
+			}
+			if n.Op() != ir.OCALLFUNC || n.(*ir.CallExpr).X.Op() != ir.OFUNCINST {
+				return
+			}
+			// We have found a function call using a generic function
+			// instantiation.
+			call := n.(*ir.CallExpr)
+			inst := call.X.(*ir.InstExpr)
+			st := g.getInstantiation(inst)
+			// Replace the OFUNCINST with a direct reference to the
+			// new stenciled function
+			call.X = st.Nname
+			if inst.X.Op() == ir.OCALLPART {
+				// When we create an instantiation of a method
+				// call, we make it a function. So, move the
+				// receiver to be the first arg of the function
+				// call.
+				withRecv := make([]ir.Node, len(call.Args)+1)
+				dot := inst.X.(*ir.SelectorExpr)
+				withRecv[0] = dot.X
+				copy(withRecv[1:], call.Args)
+				call.Args = withRecv
+			}
+			modified = true
+		})
+
+		// If we found an OFUNCINST without a corresponding call in the
+		// above decl, then traverse the nodes of decl again (with
+		// EditChildren rather than Visit), where we actually change the
+		// OFUNCINST node to an ONAME for the instantiated function.
+		// EditChildren is more expensive than Visit, so we only do this
+		// in the infrequent case of an OFUNCINSt without a corresponding
+		// call.
+		if foundFuncInst {
+			var edit func(ir.Node) ir.Node
+			edit = func(x ir.Node) ir.Node {
+				if x.Op() == ir.OFUNCINST {
+					st := g.getInstantiation(x.(*ir.InstExpr))
+					return st.Nname
+				}
+				ir.EditChildren(x, edit)
+				return x
+			}
+			edit(decl)
+		}
+		if base.Flag.W > 1 && modified {
+			ir.Dump(fmt.Sprintf("\nmodified %v", decl), decl)
+		}
+	}
+
+}
+
+// getInstantiation gets the instantiated function corresponding to inst. If the
+// instantiated function is not already cached, then it calls genericStub to
+// create the new instantiation.
+func (g *irgen) getInstantiation(inst *ir.InstExpr) *ir.Func {
+	var sym *types.Sym
+	if meth, ok := inst.X.(*ir.SelectorExpr); ok {
+		// Write the name of the generic method, including receiver type
+		sym = makeInstName(meth.Selection.Nname.Sym(), inst.Targs)
+	} else {
+		sym = makeInstName(inst.X.(*ir.Name).Name().Sym(), inst.Targs)
+	}
+	//fmt.Printf("Found generic func call in %v to %v\n", f, s)
+	st := g.target.Stencils[sym]
+	if st == nil {
+		// If instantiation doesn't exist yet, create it and add
+		// to the list of decls.
+		st = g.genericSubst(sym, inst)
+		g.target.Stencils[sym] = st
+		g.target.Decls = append(g.target.Decls, st)
+		if base.Flag.W > 1 {
+			ir.Dump(fmt.Sprintf("\nstenciled %v", st), st)
+		}
+	}
+	return st
+}
+
+// makeInstName makes the unique name for a stenciled generic function, based on
+// the name of the function and the targs.
+func makeInstName(fnsym *types.Sym, targs []ir.Node) *types.Sym {
+	b := bytes.NewBufferString("#")
+	b.WriteString(fnsym.Name)
+	b.WriteString("[")
+	for i, targ := range targs {
+		if i > 0 {
+			b.WriteString(",")
+		}
+		b.WriteString(targ.Type().String())
+	}
+	b.WriteString("]")
+	return typecheck.Lookup(b.String())
+}
+
+// Struct containing info needed for doing the substitution as we create the
+// instantiation of a generic function with specified type arguments.
+type subster struct {
+	g       *irgen
+	newf    *ir.Func // Func node for the new stenciled function
+	tparams []*types.Field
+	targs   []ir.Node
+	// The substitution map from name nodes in the generic function to the
+	// name nodes in the new stenciled function.
+	vars map[*ir.Name]*ir.Name
+	seen map[*types.Type]*types.Type
+}
+
+// genericSubst returns a new function with the specified name. The function is an
+// instantiation of a generic function or method with type params, as specified by
+// inst. For a method with a generic receiver, it returns an instantiated function
+// type where the receiver becomes the first parameter. Otherwise the instantiated
+// method would still need to be transformed by later compiler phases.
+func (g *irgen) genericSubst(name *types.Sym, inst *ir.InstExpr) *ir.Func {
+	var nameNode *ir.Name
+	var tparams []*types.Field
+	if selExpr, ok := inst.X.(*ir.SelectorExpr); ok {
+		// Get the type params from the method receiver (after skipping
+		// over any pointer)
+		nameNode = ir.AsNode(selExpr.Selection.Nname).(*ir.Name)
+		recvType := selExpr.Type().Recv().Type
+		if recvType.IsPtr() {
+			recvType = recvType.Elem()
+		}
+		tparams = make([]*types.Field, len(recvType.RParams))
+		for i, rparam := range recvType.RParams {
+			tparams[i] = types.NewField(src.NoXPos, nil, rparam)
+		}
+	} else {
+		nameNode = inst.X.(*ir.Name)
+		tparams = nameNode.Type().TParams().Fields().Slice()
+	}
+	gf := nameNode.Func
+	newf := ir.NewFunc(inst.Pos())
+	newf.Nname = ir.NewNameAt(inst.Pos(), name)
+	newf.Nname.Func = newf
+	newf.Nname.Defn = newf
+	name.Def = newf.Nname
+
+	subst := &subster{
+		g:       g,
+		newf:    newf,
+		tparams: tparams,
+		targs:   inst.Targs,
+		vars:    make(map[*ir.Name]*ir.Name),
+		seen:    make(map[*types.Type]*types.Type),
+	}
+
+	newf.Dcl = make([]*ir.Name, len(gf.Dcl))
+	for i, n := range gf.Dcl {
+		newf.Dcl[i] = subst.node(n).(*ir.Name)
+	}
+	newf.Body = subst.list(gf.Body)
+
+	// Ugly: we have to insert the Name nodes of the parameters/results into
+	// the function type. The current function type has no Nname fields set,
+	// because it came via conversion from the types2 type.
+	oldt := inst.X.Type()
+	// We also transform a generic method type to the corresponding
+	// instantiated function type where the receiver is the first parameter.
+	newt := types.NewSignature(oldt.Pkg(), nil, nil,
+		subst.fields(ir.PPARAM, append(oldt.Recvs().FieldSlice(), oldt.Params().FieldSlice()...), newf.Dcl),
+		subst.fields(ir.PPARAMOUT, oldt.Results().FieldSlice(), newf.Dcl))
+
+	newf.Nname.Ntype = ir.TypeNode(newt)
+	newf.Nname.SetType(newt)
+	ir.MarkFunc(newf.Nname)
+	newf.SetTypecheck(1)
+	newf.Nname.SetTypecheck(1)
+	// TODO(danscales) - remove later, but avoid confusion for now.
+	newf.Pragma = ir.Noinline
+	return newf
+}
+
+// node is like DeepCopy(), but creates distinct ONAME nodes, and also descends
+// into closures. It substitutes type arguments for type parameters in all the new
+// nodes.
+func (subst *subster) node(n ir.Node) ir.Node {
+	// Use closure to capture all state needed by the ir.EditChildren argument.
+	var edit func(ir.Node) ir.Node
+	edit = func(x ir.Node) ir.Node {
+		switch x.Op() {
+		case ir.OTYPE:
+			return ir.TypeNode(subst.typ(x.Type()))
+
+		case ir.ONAME:
+			name := x.(*ir.Name)
+			if v := subst.vars[name]; v != nil {
+				return v
+			}
+			m := ir.NewNameAt(name.Pos(), name.Sym())
+			if name.IsClosureVar() {
+				m.SetIsClosureVar(true)
+			}
+			t := x.Type()
+			newt := subst.typ(t)
+			m.SetType(newt)
+			m.Curfn = subst.newf
+			m.Class = name.Class
+			m.Func = name.Func
+			subst.vars[name] = m
+			m.SetTypecheck(1)
+			return m
+		case ir.OLITERAL, ir.ONIL:
+			if x.Sym() != nil {
+				return x
+			}
+		}
+		m := ir.Copy(x)
+		if _, isExpr := m.(ir.Expr); isExpr {
+			t := x.Type()
+			if t == nil {
+				// t can be nil only if this is a call that has no
+				// return values, so allow that and otherwise give
+				// an error.
+				_, isCallExpr := m.(*ir.CallExpr)
+				_, isStructKeyExpr := m.(*ir.StructKeyExpr)
+				if !isCallExpr && !isStructKeyExpr {
+					base.Fatalf(fmt.Sprintf("Nil type for %v", x))
+				}
+			} else if x.Op() != ir.OCLOSURE {
+				m.SetType(subst.typ(x.Type()))
+			}
+		}
+		ir.EditChildren(m, edit)
+
+		if x.Op() == ir.OXDOT {
+			// A method value/call via a type param will have been left as an
+			// OXDOT. When we see this during stenciling, finish the
+			// typechecking, now that we have the instantiated receiver type.
+			// We need to do this now, since the access/selection to the
+			// method for the real type is very different from the selection
+			// for the type param.
+			m.SetTypecheck(0)
+			// m will transform to an OCALLPART
+			typecheck.Expr(m)
+		}
+		if x.Op() == ir.OCALL {
+			call := m.(*ir.CallExpr)
+			if call.X.Op() == ir.OTYPE {
+				// Do typechecking on a conversion, now that we
+				// know the type argument.
+				m.SetTypecheck(0)
+				m = typecheck.Expr(m)
+			} else if call.X.Op() == ir.OCALLPART {
+				// Redo the typechecking, now that we know the method
+				// value is being called.
+				call.X.(*ir.SelectorExpr).SetOp(ir.OXDOT)
+				call.X.SetTypecheck(0)
+				call.X.SetType(nil)
+				typecheck.Callee(call.X)
+				m.SetTypecheck(0)
+				typecheck.Call(m.(*ir.CallExpr))
+			} else {
+				base.FatalfAt(call.Pos(), "Expecting OCALLPART or OTYPE with CALL")
+			}
+		}
+
+		if x.Op() == ir.OCLOSURE {
+			x := x.(*ir.ClosureExpr)
+			// Need to save/duplicate x.Func.Nname,
+			// x.Func.Nname.Ntype, x.Func.Dcl, x.Func.ClosureVars, and
+			// x.Func.Body.
+			oldfn := x.Func
+			newfn := ir.NewFunc(oldfn.Pos())
+			if oldfn.ClosureCalled() {
+				newfn.SetClosureCalled(true)
+			}
+			newfn.SetIsHiddenClosure(true)
+			m.(*ir.ClosureExpr).Func = newfn
+			newsym := makeInstName(oldfn.Nname.Sym(), subst.targs)
+			newfn.Nname = ir.NewNameAt(oldfn.Nname.Pos(), newsym)
+			newfn.Nname.Func = newfn
+			newfn.Nname.Defn = newfn
+			ir.MarkFunc(newfn.Nname)
+			newfn.OClosure = m.(*ir.ClosureExpr)
+
+			saveNewf := subst.newf
+			subst.newf = newfn
+			newfn.Dcl = subst.namelist(oldfn.Dcl)
+			newfn.ClosureVars = subst.namelist(oldfn.ClosureVars)
+			newfn.Body = subst.list(oldfn.Body)
+			subst.newf = saveNewf
+
+			// Set Ntype for now to be compatible with later parts of compiler
+			newfn.Nname.Ntype = subst.node(oldfn.Nname.Ntype).(ir.Ntype)
+			typed(subst.typ(oldfn.Nname.Type()), newfn.Nname)
+			newfn.SetTypecheck(1)
+			subst.g.target.Decls = append(subst.g.target.Decls, newfn)
+		}
+		return m
+	}
+
+	return edit(n)
+}
+
+func (subst *subster) namelist(l []*ir.Name) []*ir.Name {
+	s := make([]*ir.Name, len(l))
+	for i, n := range l {
+		s[i] = subst.node(n).(*ir.Name)
+		if n.Defn != nil {
+			s[i].Defn = subst.node(n.Defn)
+		}
+		if n.Outer != nil {
+			s[i].Outer = subst.node(n.Outer).(*ir.Name)
+		}
+	}
+	return s
+}
+
+func (subst *subster) list(l []ir.Node) []ir.Node {
+	s := make([]ir.Node, len(l))
+	for i, n := range l {
+		s[i] = subst.node(n)
+	}
+	return s
+}
+
+// tstruct substitutes type params in types of the fields of a structure type. For
+// each field, if Nname is set, tstruct also translates the Nname using subst.vars, if
+// Nname is in subst.vars.
+func (subst *subster) tstruct(t *types.Type) *types.Type {
+	if t.NumFields() == 0 {
+		return t
+	}
+	var newfields []*types.Field
+	for i, f := range t.Fields().Slice() {
+		t2 := subst.typ(f.Type)
+		if (t2 != f.Type || f.Nname != nil) && newfields == nil {
+			newfields = make([]*types.Field, t.NumFields())
+			for j := 0; j < i; j++ {
+				newfields[j] = t.Field(j)
+			}
+		}
+		if newfields != nil {
+			newfields[i] = types.NewField(f.Pos, f.Sym, t2)
+			if f.Nname != nil {
+				// f.Nname may not be in subst.vars[] if this is
+				// a function name or a function instantiation type
+				// that we are translating
+				newfields[i].Nname = subst.vars[f.Nname.(*ir.Name)]
+			}
+		}
+	}
+	if newfields != nil {
+		return types.NewStruct(t.Pkg(), newfields)
+	}
+	return t
+
+}
+
+// instTypeName creates a name for an instantiated type, based on the type args
+func instTypeName(name string, targs []*types.Type) string {
+	b := bytes.NewBufferString(name)
+	b.WriteByte('[')
+	for i, targ := range targs {
+		if i > 0 {
+			b.WriteByte(',')
+		}
+		b.WriteString(targ.String())
+	}
+	b.WriteByte(']')
+	return b.String()
+}
+
+// typ computes the type obtained by substituting any type parameter in t with the
+// corresponding type argument in subst. If t contains no type parameters, the
+// result is t; otherwise the result is a new type.
+// It deals with recursive types by using a map and TFORW types.
+// TODO(danscales) deal with recursion besides ptr/struct cases.
+func (subst *subster) typ(t *types.Type) *types.Type {
+	if !t.HasTParam() {
+		return t
+	}
+	if subst.seen[t] != nil {
+		// We've hit a recursive type
+		return subst.seen[t]
+	}
+
+	var newt *types.Type
+	switch t.Kind() {
+	case types.TTYPEPARAM:
+		for i, tp := range subst.tparams {
+			if tp.Type == t {
+				return subst.targs[i].Type()
+			}
+		}
+		return t
+
+	case types.TARRAY:
+		elem := t.Elem()
+		newelem := subst.typ(elem)
+		if newelem != elem {
+			newt = types.NewArray(newelem, t.NumElem())
+		}
+
+	case types.TPTR:
+		elem := t.Elem()
+		// In order to deal with recursive generic types, create a TFORW
+		// type initially and store it in the seen map, so it can be
+		// accessed if this type appears recursively within the type.
+		forw := types.New(types.TFORW)
+		subst.seen[t] = forw
+		newelem := subst.typ(elem)
+		if newelem != elem {
+			forw.SetUnderlying(types.NewPtr(newelem))
+			newt = forw
+		}
+		delete(subst.seen, t)
+
+	case types.TSLICE:
+		elem := t.Elem()
+		newelem := subst.typ(elem)
+		if newelem != elem {
+			newt = types.NewSlice(newelem)
+		}
+
+	case types.TSTRUCT:
+		forw := types.New(types.TFORW)
+		subst.seen[t] = forw
+		newt = subst.tstruct(t)
+		if newt != t {
+			forw.SetUnderlying(newt)
+			newt = forw
+		}
+		delete(subst.seen, t)
+
+	case types.TFUNC:
+		newrecvs := subst.tstruct(t.Recvs())
+		newparams := subst.tstruct(t.Params())
+		newresults := subst.tstruct(t.Results())
+		if newrecvs != t.Recvs() || newparams != t.Params() || newresults != t.Results() {
+			var newrecv *types.Field
+			if newrecvs.NumFields() > 0 {
+				newrecv = newrecvs.Field(0)
+			}
+			newt = types.NewSignature(t.Pkg(), newrecv, nil, newparams.FieldSlice(), newresults.FieldSlice())
+		}
+
+		// TODO: case TCHAN
+		// TODO: case TMAP
+		// TODO: case TINTER
+	}
+	if newt != nil {
+		if t.Sym() != nil {
+			// Since we've substituted types, we also need to change
+			// the defined name of the type, by removing the old types
+			// (in brackets) from the name, and adding the new types.
+
+			// Translate the type params for this type according to
+			// the tparam/targs mapping of the function.
+			neededTargs := make([]*types.Type, len(t.RParams))
+			for i, rparam := range t.RParams {
+				neededTargs[i] = subst.typ(rparam)
+			}
+			oldname := t.Sym().Name
+			i := strings.Index(oldname, "[")
+			oldname = oldname[:i]
+			sym := t.Sym().Pkg.Lookup(instTypeName(oldname, neededTargs))
+			if sym.Def != nil {
+				// We've already created this instantiated defined type.
+				return sym.Def.Type()
+			}
+			newt.SetSym(sym)
+			sym.Def = ir.TypeNode(newt)
+		}
+		return newt
+	}
+
+	return t
+}
+
+// fields sets the Nname field for the Field nodes inside a type signature, based
+// on the corresponding in/out parameters in dcl. It depends on the in and out
+// parameters being in order in dcl.
+func (subst *subster) fields(class ir.Class, oldfields []*types.Field, dcl []*ir.Name) []*types.Field {
+	newfields := make([]*types.Field, len(oldfields))
+	var i int
+
+	// Find the starting index in dcl of declarations of the class (either
+	// PPARAM or PPARAMOUT).
+	for i = range dcl {
+		if dcl[i].Class == class {
+			break
+		}
+	}
+
+	// Create newfields nodes that are copies of the oldfields nodes, but
+	// with substitution for any type params, and with Nname set to be the node in
+	// Dcl for the corresponding PPARAM or PPARAMOUT.
+	for j := range oldfields {
+		newfields[j] = oldfields[j].Copy()
+		newfields[j].Type = subst.typ(oldfields[j].Type)
+		newfields[j].Nname = dcl[i]
+		i++
+	}
+	return newfields
+}

src/cmd/compile/internal/noder/stmt.go

@@ -0,0 +1,303 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package noder
+
+import (
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/syntax"
+	"cmd/compile/internal/typecheck"
+	"cmd/compile/internal/types"
+	"cmd/internal/src"
+)
+
+func (g *irgen) stmts(stmts []syntax.Stmt) []ir.Node {
+	var nodes []ir.Node
+	for _, stmt := range stmts {
+		switch s := g.stmt(stmt).(type) {
+		case nil: // EmptyStmt
+		case *ir.BlockStmt:
+			nodes = append(nodes, s.List...)
+		default:
+			nodes = append(nodes, s)
+		}
+	}
+	return nodes
+}
+
+func (g *irgen) stmt(stmt syntax.Stmt) ir.Node {
+	// TODO(mdempsky): Remove dependency on typecheck.
+	return typecheck.Stmt(g.stmt0(stmt))
+}
+
+func (g *irgen) stmt0(stmt syntax.Stmt) ir.Node {
+	switch stmt := stmt.(type) {
+	case nil, *syntax.EmptyStmt:
+		return nil
+	case *syntax.LabeledStmt:
+		return g.labeledStmt(stmt)
+	case *syntax.BlockStmt:
+		return ir.NewBlockStmt(g.pos(stmt), g.blockStmt(stmt))
+	case *syntax.ExprStmt:
+		x := g.expr(stmt.X)
+		if call, ok := x.(*ir.CallExpr); ok {
+			call.Use = ir.CallUseStmt
+		}
+		return x
+	case *syntax.SendStmt:
+		return ir.NewSendStmt(g.pos(stmt), g.expr(stmt.Chan), g.expr(stmt.Value))
+	case *syntax.DeclStmt:
+		return ir.NewBlockStmt(g.pos(stmt), g.decls(stmt.DeclList))
+
+	case *syntax.AssignStmt:
+		if stmt.Op != 0 && stmt.Op != syntax.Def {
+			op := g.op(stmt.Op, binOps[:])
+			if stmt.Rhs == nil {
+				return IncDec(g.pos(stmt), op, g.expr(stmt.Lhs))
+			}
+			return ir.NewAssignOpStmt(g.pos(stmt), op, g.expr(stmt.Lhs), g.expr(stmt.Rhs))
+		}
+
+		names, lhs := g.assignList(stmt.Lhs, stmt.Op == syntax.Def)
+		rhs := g.exprList(stmt.Rhs)
+
+		if len(lhs) == 1 && len(rhs) == 1 {
+			n := ir.NewAssignStmt(g.pos(stmt), lhs[0], rhs[0])
+			n.Def = initDefn(n, names)
+			return n
+		}
+
+		n := ir.NewAssignListStmt(g.pos(stmt), ir.OAS2, lhs, rhs)
+		n.Def = initDefn(n, names)
+		return n
+
+	case *syntax.BranchStmt:
+		return ir.NewBranchStmt(g.pos(stmt), g.tokOp(int(stmt.Tok), branchOps[:]), g.name(stmt.Label))
+	case *syntax.CallStmt:
+		return ir.NewGoDeferStmt(g.pos(stmt), g.tokOp(int(stmt.Tok), callOps[:]), g.expr(stmt.Call))
+	case *syntax.ReturnStmt:
+		return ir.NewReturnStmt(g.pos(stmt), g.exprList(stmt.Results))
+	case *syntax.IfStmt:
+		return g.ifStmt(stmt)
+	case *syntax.ForStmt:
+		return g.forStmt(stmt)
+	case *syntax.SelectStmt:
+		return g.selectStmt(stmt)
+	case *syntax.SwitchStmt:
+		return g.switchStmt(stmt)
+
+	default:
+		g.unhandled("statement", stmt)
+		panic("unreachable")
+	}
+}
+
+// TODO(mdempsky): Investigate replacing with switch statements or dense arrays.
+
+var branchOps = [...]ir.Op{
+	syntax.Break:       ir.OBREAK,
+	syntax.Continue:    ir.OCONTINUE,
+	syntax.Fallthrough: ir.OFALL,
+	syntax.Goto:        ir.OGOTO,
+}
+
+var callOps = [...]ir.Op{
+	syntax.Defer: ir.ODEFER,
+	syntax.Go:    ir.OGO,
+}
+
+func (g *irgen) tokOp(tok int, ops []ir.Op) ir.Op {
+	// TODO(mdempsky): Validate.
+	return ops[tok]
+}
+
+func (g *irgen) op(op syntax.Operator, ops []ir.Op) ir.Op {
+	// TODO(mdempsky): Validate.
+	return ops[op]
+}
+
+func (g *irgen) assignList(expr syntax.Expr, def bool) ([]*ir.Name, []ir.Node) {
+	if !def {
+		return nil, g.exprList(expr)
+	}
+
+	var exprs []syntax.Expr
+	if list, ok := expr.(*syntax.ListExpr); ok {
+		exprs = list.ElemList
+	} else {
+		exprs = []syntax.Expr{expr}
+	}
+
+	var names []*ir.Name
+	res := make([]ir.Node, len(exprs))
+	for i, expr := range exprs {
+		expr := expr.(*syntax.Name)
+		if expr.Value == "_" {
+			res[i] = ir.BlankNode
+			continue
+		}
+
+		if obj, ok := g.info.Uses[expr]; ok {
+			res[i] = g.obj(obj)
+			continue
+		}
+
+		name, _ := g.def(expr)
+		names = append(names, name)
+		res[i] = name
+	}
+
+	return names, res
+}
+
+// initDefn marks the given names as declared by defn and populates
+// its Init field with ODCL nodes. It then reports whether any names
+// were so declared, which can be used to initialize defn.Def.
+func initDefn(defn ir.InitNode, names []*ir.Name) bool {
+	if len(names) == 0 {
+		return false
+	}
+
+	init := make([]ir.Node, len(names))
+	for i, name := range names {
+		name.Defn = defn
+		init[i] = ir.NewDecl(name.Pos(), ir.ODCL, name)
+	}
+	defn.SetInit(init)
+	return true
+}
+
+func (g *irgen) blockStmt(stmt *syntax.BlockStmt) []ir.Node {
+	return g.stmts(stmt.List)
+}
+
+func (g *irgen) ifStmt(stmt *syntax.IfStmt) ir.Node {
+	init := g.stmt(stmt.Init)
+	n := ir.NewIfStmt(g.pos(stmt), g.expr(stmt.Cond), g.blockStmt(stmt.Then), nil)
+	if stmt.Else != nil {
+		e := g.stmt(stmt.Else)
+		if e.Op() == ir.OBLOCK {
+			e := e.(*ir.BlockStmt)
+			n.Else = e.List
+		} else {
+			n.Else = []ir.Node{e}
+		}
+	}
+	return g.init(init, n)
+}
+
+// unpackTwo returns the first two nodes in list. If list has fewer
+// than 2 nodes, then the missing nodes are replaced with nils.
+func unpackTwo(list []ir.Node) (fst, snd ir.Node) {
+	switch len(list) {
+	case 0:
+		return nil, nil
+	case 1:
+		return list[0], nil
+	default:
+		return list[0], list[1]
+	}
+}
+
+func (g *irgen) forStmt(stmt *syntax.ForStmt) ir.Node {
+	if r, ok := stmt.Init.(*syntax.RangeClause); ok {
+		names, lhs := g.assignList(r.Lhs, r.Def)
+		key, value := unpackTwo(lhs)
+		n := ir.NewRangeStmt(g.pos(r), key, value, g.expr(r.X), g.blockStmt(stmt.Body))
+		n.Def = initDefn(n, names)
+		return n
+	}
+
+	return ir.NewForStmt(g.pos(stmt), g.stmt(stmt.Init), g.expr(stmt.Cond), g.stmt(stmt.Post), g.blockStmt(stmt.Body))
+}
+
+func (g *irgen) selectStmt(stmt *syntax.SelectStmt) ir.Node {
+	body := make([]*ir.CommClause, len(stmt.Body))
+	for i, clause := range stmt.Body {
+		body[i] = ir.NewCommStmt(g.pos(clause), g.stmt(clause.Comm), g.stmts(clause.Body))
+	}
+	return ir.NewSelectStmt(g.pos(stmt), body)
+}
+
+func (g *irgen) switchStmt(stmt *syntax.SwitchStmt) ir.Node {
+	pos := g.pos(stmt)
+	init := g.stmt(stmt.Init)
+
+	var expr ir.Node
+	switch tag := stmt.Tag.(type) {
+	case *syntax.TypeSwitchGuard:
+		var ident *ir.Ident
+		if tag.Lhs != nil {
+			ident = ir.NewIdent(g.pos(tag.Lhs), g.name(tag.Lhs))
+		}
+		expr = ir.NewTypeSwitchGuard(pos, ident, g.expr(tag.X))
+	default:
+		expr = g.expr(tag)
+	}
+
+	body := make([]*ir.CaseClause, len(stmt.Body))
+	for i, clause := range stmt.Body {
+		// Check for an implicit clause variable before
+		// visiting body, because it may contain function
+		// literals that reference it, and then it'll be
+		// associated to the wrong function.
+		//
+		// Also, override its position to the clause's colon, so that
+		// dwarfgen can find the right scope for it later.
+		// TODO(mdempsky): We should probably just store the scope
+		// directly in the ir.Name.
+		var cv *ir.Name
+		if obj, ok := g.info.Implicits[clause]; ok {
+			cv = g.obj(obj)
+			cv.SetPos(g.makeXPos(clause.Colon))
+		}
+		body[i] = ir.NewCaseStmt(g.pos(clause), g.exprList(clause.Cases), g.stmts(clause.Body))
+		body[i].Var = cv
+	}
+
+	return g.init(init, ir.NewSwitchStmt(pos, expr, body))
+}
+
+func (g *irgen) labeledStmt(label *syntax.LabeledStmt) ir.Node {
+	sym := g.name(label.Label)
+	lhs := ir.NewLabelStmt(g.pos(label), sym)
+	ls := g.stmt(label.Stmt)
+
+	// Attach label directly to control statement too.
+	switch ls := ls.(type) {
+	case *ir.ForStmt:
+		ls.Label = sym
+	case *ir.RangeStmt:
+		ls.Label = sym
+	case *ir.SelectStmt:
+		ls.Label = sym
+	case *ir.SwitchStmt:
+		ls.Label = sym
+	}
+
+	l := []ir.Node{lhs}
+	if ls != nil {
+		if ls.Op() == ir.OBLOCK {
+			ls := ls.(*ir.BlockStmt)
+			l = append(l, ls.List...)
+		} else {
+			l = append(l, ls)
+		}
+	}
+	return ir.NewBlockStmt(src.NoXPos, l)
+}
+
+func (g *irgen) init(init ir.Node, stmt ir.InitNode) ir.InitNode {
+	if init != nil {
+		stmt.SetInit([]ir.Node{init})
+	}
+	return stmt
+}
+
+func (g *irgen) name(name *syntax.Name) *types.Sym {
+	if name == nil {
+		return nil
+	}
+	return typecheck.Lookup(name.Value)
+}

src/cmd/compile/internal/noder/types.go

@@ -0,0 +1,328 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package noder
+
+import (
+	"bytes"
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/ir"
+	"cmd/compile/internal/typecheck"
+	"cmd/compile/internal/types"
+	"cmd/compile/internal/types2"
+	"cmd/internal/src"
+)
+
+func (g *irgen) pkg(pkg *types2.Package) *types.Pkg {
+	switch pkg {
+	case nil:
+		return types.BuiltinPkg
+	case g.self:
+		return types.LocalPkg
+	case types2.Unsafe:
+		return ir.Pkgs.Unsafe
+	}
+	return types.NewPkg(pkg.Path(), pkg.Name())
+}
+
+// typ converts a types2.Type to a types.Type, including caching of previously
+// translated types.
+func (g *irgen) typ(typ types2.Type) *types.Type {
+	// Caching type mappings isn't strictly needed, because typ0 preserves
+	// type identity; but caching minimizes memory blow-up from mapping the
+	// same composite type multiple times, and also plays better with the
+	// current state of cmd/compile (e.g., haphazard calculation of type
+	// sizes).
+	res, ok := g.typs[typ]
+	if !ok {
+		res = g.typ0(typ)
+		g.typs[typ] = res
+
+		// Ensure we calculate the size for all concrete types seen by
+		// the frontend. This is another heavy hammer for something that
+		// should really be the backend's responsibility instead.
+		if res != nil && !res.IsUntyped() && !res.IsFuncArgStruct() {
+			types.CheckSize(res)
+		}
+	}
+	return res
+}
+
+// instTypeName2 creates a name for an instantiated type, base on the type args
+// (given as types2 types).
+func instTypeName2(name string, targs []types2.Type) string {
+	b := bytes.NewBufferString(name)
+	b.WriteByte('[')
+	for i, targ := range targs {
+		if i > 0 {
+			b.WriteByte(',')
+		}
+		b.WriteString(types2.TypeString(targ,
+			func(*types2.Package) string { return "" }))
+	}
+	b.WriteByte(']')
+	return b.String()
+}
+
+// typ0 converts a types2.Type to a types.Type, but doesn't do the caching check
+// at the top level.
+func (g *irgen) typ0(typ types2.Type) *types.Type {
+	switch typ := typ.(type) {
+	case *types2.Basic:
+		return g.basic(typ)
+	case *types2.Named:
+		if typ.TParams() != nil {
+			// typ is an instantiation of a defined (named) generic type.
+			// This instantiation should also be a defined (named) type.
+			// types2 gives us the substituted type in t.Underlying()
+			// The substituted type may or may not still have type
+			// params. We might, for example, be substituting one type
+			// param for another type param.
+
+			if typ.TArgs() == nil {
+				base.Fatalf("In typ0, Targs should be set if TParams is set")
+			}
+
+			// When converted to types.Type, typ must have a name,
+			// based on the names of the type arguments. We need a
+			// name to deal with recursive generic types (and it also
+			// looks better when printing types).
+			instName := instTypeName2(typ.Obj().Name(), typ.TArgs())
+			s := g.pkg(typ.Obj().Pkg()).Lookup(instName)
+			if s.Def != nil {
+				// We have already encountered this instantiation,
+				// so use the type we previously created, since there
+				// must be exactly one instance of a defined type.
+				return s.Def.Type()
+			}
+
+			// Create a forwarding type first and put it in the g.typs
+			// map, in order to deal with recursive generic types.
+			ntyp := types.New(types.TFORW)
+			g.typs[typ] = ntyp
+			ntyp.SetUnderlying(g.typ(typ.Underlying()))
+			ntyp.SetSym(s)
+
+			if ntyp.HasTParam() {
+				// If ntyp still has type params, then we must be
+				// referencing something like 'value[T2]', as when
+				// specifying the generic receiver of a method,
+				// where value was defined as "type value[T any]
+				// ...". Save the type args, which will now be the
+				// new type params of the current type.
+				ntyp.RParams = make([]*types.Type, len(typ.TArgs()))
+				for i, targ := range typ.TArgs() {
+					ntyp.RParams[i] = g.typ(targ)
+				}
+			}
+
+			// Make sure instantiated type can be uniquely found from
+			// the sym
+			s.Def = ir.TypeNode(ntyp)
+			return ntyp
+		}
+		obj := g.obj(typ.Obj())
+		if obj.Op() != ir.OTYPE {
+			base.FatalfAt(obj.Pos(), "expected type: %L", obj)
+		}
+		return obj.Type()
+
+	case *types2.Array:
+		return types.NewArray(g.typ(typ.Elem()), typ.Len())
+	case *types2.Chan:
+		return types.NewChan(g.typ(typ.Elem()), dirs[typ.Dir()])
+	case *types2.Map:
+		return types.NewMap(g.typ(typ.Key()), g.typ(typ.Elem()))
+	case *types2.Pointer:
+		return types.NewPtr(g.typ(typ.Elem()))
+	case *types2.Signature:
+		return g.signature(nil, typ)
+	case *types2.Slice:
+		return types.NewSlice(g.typ(typ.Elem()))
+
+	case *types2.Struct:
+		fields := make([]*types.Field, typ.NumFields())
+		for i := range fields {
+			v := typ.Field(i)
+			f := types.NewField(g.pos(v), g.selector(v), g.typ(v.Type()))
+			f.Note = typ.Tag(i)
+			if v.Embedded() {
+				f.Embedded = 1
+			}
+			fields[i] = f
+		}
+		return types.NewStruct(g.tpkg(typ), fields)
+
+	case *types2.Interface:
+		embeddeds := make([]*types.Field, typ.NumEmbeddeds())
+		for i := range embeddeds {
+			// TODO(mdempsky): Get embedding position.
+			e := typ.EmbeddedType(i)
+			embeddeds[i] = types.NewField(src.NoXPos, nil, g.typ(e))
+		}
+
+		methods := make([]*types.Field, typ.NumExplicitMethods())
+		for i := range methods {
+			m := typ.ExplicitMethod(i)
+			mtyp := g.signature(typecheck.FakeRecv(), m.Type().(*types2.Signature))
+			methods[i] = types.NewField(g.pos(m), g.selector(m), mtyp)
+		}
+
+		return types.NewInterface(g.tpkg(typ), append(embeddeds, methods...))
+
+	case *types2.TypeParam:
+		tp := types.NewTypeParam(g.tpkg(typ), g.typ(typ.Bound()))
+		// Save the name of the type parameter in the sym of the type.
+		tp.SetSym(g.sym(typ.Obj()))
+		return tp
+
+	case *types2.Tuple:
+		// Tuples are used for the type of a function call (i.e. the
+		// return value of the function).
+		if typ == nil {
+			return (*types.Type)(nil)
+		}
+		fields := make([]*types.Field, typ.Len())
+		for i := range fields {
+			fields[i] = g.param(typ.At(i))
+		}
+		t := types.NewStruct(types.LocalPkg, fields)
+		types.CheckSize(t)
+		// Can only set after doing the types.CheckSize()
+		t.StructType().Funarg = types.FunargResults
+		return t
+
+	default:
+		base.FatalfAt(src.NoXPos, "unhandled type: %v (%T)", typ, typ)
+		panic("unreachable")
+	}
+}
+
+func (g *irgen) signature(recv *types.Field, sig *types2.Signature) *types.Type {
+	tparams2 := sig.TParams()
+	tparams := make([]*types.Field, len(tparams2))
+	for i := range tparams {
+		tp := tparams2[i]
+		tparams[i] = types.NewField(g.pos(tp), g.sym(tp), g.typ(tp.Type()))
+	}
+
+	do := func(typ *types2.Tuple) []*types.Field {
+		fields := make([]*types.Field, typ.Len())
+		for i := range fields {
+			fields[i] = g.param(typ.At(i))
+		}
+		return fields
+	}
+	params := do(sig.Params())
+	results := do(sig.Results())
+	if sig.Variadic() {
+		params[len(params)-1].SetIsDDD(true)
+	}
+
+	return types.NewSignature(g.tpkg(sig), recv, tparams, params, results)
+}
+
+func (g *irgen) param(v *types2.Var) *types.Field {
+	return types.NewField(g.pos(v), g.sym(v), g.typ(v.Type()))
+}
+
+func (g *irgen) sym(obj types2.Object) *types.Sym {
+	if name := obj.Name(); name != "" {
+		return g.pkg(obj.Pkg()).Lookup(obj.Name())
+	}
+	return nil
+}
+
+func (g *irgen) selector(obj types2.Object) *types.Sym {
+	pkg, name := g.pkg(obj.Pkg()), obj.Name()
+	if types.IsExported(name) {
+		pkg = types.LocalPkg
+	}
+	return pkg.Lookup(name)
+}
+
+// tpkg returns the package that a function, interface, or struct type
+// expression appeared in.
+//
+// Caveat: For the degenerate types "func()", "interface{}", and
+// "struct{}", tpkg always returns LocalPkg. However, we only need the
+// package information so that go/types can report it via its API, and
+// the reason we fail to return the original package for these
+// particular types is because go/types does *not* report it for
+// them. So in practice this limitation is probably moot.
+func (g *irgen) tpkg(typ types2.Type) *types.Pkg {
+	anyObj := func() types2.Object {
+		switch typ := typ.(type) {
+		case *types2.Signature:
+			if recv := typ.Recv(); recv != nil {
+				return recv
+			}
+			if params := typ.Params(); params.Len() > 0 {
+				return params.At(0)
+			}
+			if results := typ.Results(); results.Len() > 0 {
+				return results.At(0)
+			}
+		case *types2.Struct:
+			if typ.NumFields() > 0 {
+				return typ.Field(0)
+			}
+		case *types2.Interface:
+			if typ.NumExplicitMethods() > 0 {
+				return typ.ExplicitMethod(0)
+			}
+		}
+		return nil
+	}
+
+	if obj := anyObj(); obj != nil {
+		return g.pkg(obj.Pkg())
+	}
+	return types.LocalPkg
+}
+
+func (g *irgen) basic(typ *types2.Basic) *types.Type {
+	switch typ.Name() {
+	case "byte":
+		return types.ByteType
+	case "rune":
+		return types.RuneType
+	}
+	return *basics[typ.Kind()]
+}
+
+var basics = [...]**types.Type{
+	types2.Invalid:        new(*types.Type),
+	types2.Bool:           &types.Types[types.TBOOL],
+	types2.Int:            &types.Types[types.TINT],
+	types2.Int8:           &types.Types[types.TINT8],
+	types2.Int16:          &types.Types[types.TINT16],
+	types2.Int32:          &types.Types[types.TINT32],
+	types2.Int64:          &types.Types[types.TINT64],
+	types2.Uint:           &types.Types[types.TUINT],
+	types2.Uint8:          &types.Types[types.TUINT8],
+	types2.Uint16:         &types.Types[types.TUINT16],
+	types2.Uint32:         &types.Types[types.TUINT32],
+	types2.Uint64:         &types.Types[types.TUINT64],
+	types2.Uintptr:        &types.Types[types.TUINTPTR],
+	types2.Float32:        &types.Types[types.TFLOAT32],
+	types2.Float64:        &types.Types[types.TFLOAT64],
+	types2.Complex64:      &types.Types[types.TCOMPLEX64],
+	types2.Complex128:     &types.Types[types.TCOMPLEX128],
+	types2.String:         &types.Types[types.TSTRING],
+	types2.UnsafePointer:  &types.Types[types.TUNSAFEPTR],
+	types2.UntypedBool:    &types.UntypedBool,
+	types2.UntypedInt:     &types.UntypedInt,
+	types2.UntypedRune:    &types.UntypedRune,
+	types2.UntypedFloat:   &types.UntypedFloat,
+	types2.UntypedComplex: &types.UntypedComplex,
+	types2.UntypedString:  &types.UntypedString,
+	types2.UntypedNil:     &types.Types[types.TNIL],
+}
+
+var dirs = [...]types.ChanDir{
+	types2.SendRecv: types.Cboth,
+	types2.SendOnly: types.Csend,
+	types2.RecvOnly: types.Crecv,
+}

src/cmd/compile/internal/noder/validate.go

@@ -0,0 +1,113 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package noder
+
+import (
+	"go/constant"
+
+	"cmd/compile/internal/base"
+	"cmd/compile/internal/syntax"
+	"cmd/compile/internal/types"
+	"cmd/compile/internal/types2"
+)
+
+// match reports whether types t1 and t2 are consistent
+// representations for a given expression's type.
+func (g *irgen) match(t1 *types.Type, t2 types2.Type, hasOK bool) bool {
+	tuple, ok := t2.(*types2.Tuple)
+	if !ok {
+		// Not a tuple; can use simple type identity comparison.
+		return types.Identical(t1, g.typ(t2))
+	}
+
+	if hasOK {
+		// For has-ok values, types2 represents the expression's type as
+		// a 2-element tuple, whereas ir just uses the first type and
+		// infers that the second type is boolean.
+		return tuple.Len() == 2 && types.Identical(t1, g.typ(tuple.At(0).Type()))
+	}
+
+	if t1 == nil || tuple == nil {
+		return t1 == nil && tuple == nil
+	}
+	if !t1.IsFuncArgStruct() {
+		return false
+	}
+	if t1.NumFields() != tuple.Len() {
+		return false
+	}
+	for i, result := range t1.FieldSlice() {
+		if !types.Identical(result.Type, g.typ(tuple.At(i).Type())) {
+			return false
+		}
+	}
+	return true
+}
+
+func (g *irgen) validate(n syntax.Node) {
+	switch n := n.(type) {
+	case *syntax.CallExpr:
+		tv := g.info.Types[n.Fun]
+		if tv.IsBuiltin() {
+			switch builtin := n.Fun.(type) {
+			case *syntax.Name:
+				g.validateBuiltin(builtin.Value, n)
+			case *syntax.SelectorExpr:
+				g.validateBuiltin(builtin.Sel.Value, n)
+			default:
+				g.unhandled("builtin", n)
+			}
+		}
+	}
+}
+
+func (g *irgen) validateBuiltin(name string, call *syntax.CallExpr) {
+	switch name {
+	case "Alignof", "Offsetof", "Sizeof":
+		// Check that types2+gcSizes calculates sizes the same
+		// as cmd/compile does.
+
+		got, ok := constant.Int64Val(g.info.Types[call].Value)
+		if !ok {
+			base.FatalfAt(g.pos(call), "expected int64 constant value")
+		}
+
+		want := g.unsafeExpr(name, call.ArgList[0])
+		if got != want {
+			base.FatalfAt(g.pos(call), "got %v from types2, but want %v", got, want)
+		}
+	}
+}
+
+// unsafeExpr evaluates the given unsafe builtin function on arg.
+func (g *irgen) unsafeExpr(name string, arg syntax.Expr) int64 {
+	switch name {
+	case "Alignof":
+		return g.typ(g.info.Types[arg].Type).Alignment()
+	case "Sizeof":
+		return g.typ(g.info.Types[arg].Type).Size()
+	}
+
+	// Offsetof
+
+	sel := arg.(*syntax.SelectorExpr)
+	selection := g.info.Selections[sel]
+
+	typ := g.typ(g.info.Types[sel.X].Type)
+	if typ.IsPtr() {
+		typ = typ.Elem()
+	}
+
+	var offset int64
+	for _, i := range selection.Index() {
+		// Ensure field offsets have been calculated.
+		types.CalcSize(typ)
+
+		f := typ.Field(i)
+		offset += f.Offset
+		typ = f.Type
+	}
+	return offset
+}