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cmd/compile: propagate len([]T{}) to make builtin to allow stack allocation

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Updates #75620

Change-Id: I6a6a6964af4512e30eb4806e1dc7b0fd0835744f
Reviewed-on: https://go-review.googlesource.com/c/go/+/707255
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Carlos Amedee <carlos@golang.org>
This commit is contained in:
Mateusz Poliwczak
2025-09-26 20:47:45 +02:00
committed by Gopher Robot
parent 5799c139a7
commit 84db201ae1
2 changed files with 27 additions and 1 deletions
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13
src/cmd/compile/internal/escape/escape.go
View File

@@ -563,7 +563,10 @@ func (b *batch) rewriteWithLiterals(n ir.Node, fn *ir.Func) {
if ro == nil {
base.Fatalf("no ReassignOracle for function %v with closure parent %v", fn, fn.ClosureParent)
}
if s := ro.StaticValue(*r); s.Op() == ir.OLITERAL {
s := ro.StaticValue(*r)
switch s.Op() {
case ir.OLITERAL:
lit, ok := s.(*ir.BasicLit)
if !ok || lit.Val().Kind() != constant.Int {
base.Fatalf("unexpected BasicLit Kind")
@@ -577,6 +580,14 @@ func (b *batch) rewriteWithLiterals(n ir.Node, fn *ir.Func) {
assignTemp(n.Pos(), *r, n.PtrInit())
*r = ir.NewBasicLit(n.Pos(), (*r).Type(), lit.Val())
}
case ir.OLEN:
x := ro.StaticValue(s.(*ir.UnaryExpr).X)
if x.Op() == ir.OSLICELIT {
x := x.(*ir.CompLitExpr)
// Preserve any side effects of the original expression, then update the value.
assignTemp(n.Pos(), *r, n.PtrInit())
*r = ir.NewBasicLit(n.Pos(), types.Types[types.TINT], constant.MakeInt64(x.Len))
}
}
}
case ir.OCONVIFACE:

15
test/escape_make_non_const.go
View File

@@ -106,3 +106,18 @@ type m struct {
func newM(l int) m { // ERROR "can inline"
return m{make(map[string]int, l)} // ERROR "make.*escapes to heap"
}
//go:noinline
func testLenOfSliceLit() {
ints := []int{0, 1, 2, 3, 4, 5} // ERROR "\[\]int\{\.\.\.\} does not escape"'
_ = make([]int, len(ints)) // ERROR "make\(\[\]int, 6\) does not escape"
_ = allocLenOf(ints) // ERROR "inlining call", "make\(\[\]int, 6\) does not escape"
_ = make([]int, 2, len(ints)) // ERROR "make\(\[\]int, 2, 6\) does not escape"
_ = make([]int, len(ints), 2) // ERROR "make\(\[\]int, len\(ints\), 2\) does not escape"
_ = make([]int, 10, len(ints)) // ERROR "make\(\[\]int, 10, 6\) does not escape"
}
func allocLenOf(s []int) []int { // ERROR "can inline" "s does not escape"
return make([]int, len(s)) // ERROR "escapes to heap"
}