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cpu: fix AVX512 support detection on Darwin

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Summary: On darwin/amd64, it is not adequate to use OSXSAVE
bits to determine AVX512 availabilty. The reason is involved.
See github issue for details.

The fix consists of implementing Apple's recommended approach
using the process commpage cpu_capabilities bits to determine
availability of AVX512.

Fixes golang/go#43089

Change-Id: I1ba89965498863d268fbf2e427dbfd6429c7409f
Reviewed-on: https://go-review.googlesource.com/c/sys/+/285572
Trust: Tobias Klauser <tobias.klauser@gmail.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Martin Möhrmann <moehrmann@google.com>
This commit is contained in:
Vaughn Iverson
2021-01-21 16:49:49 -08:00
committed by Martin Möhrmann
parent 71e4cd670f
commit b677753862
4 changed files with 42 additions and 2 deletions
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4
cpu/cpu_gc_x86.go
View File

@@ -15,3 +15,7 @@ func cpuid(eaxArg, ecxArg uint32) (eax, ebx, ecx, edx uint32)
// xgetbv with ecx = 0 is implemented in cpu_x86.s for gc compiler
// and in cpu_gccgo.c for gccgo.
func xgetbv() (eax, edx uint32)
// darwinSupportsAVX512 is implemented in cpu_x86.s for gc compiler
// and in cpu_gccgo_x86.go for gccgo.
func darwinSupportsAVX512() bool

6
cpu/cpu_gccgo_x86.go
View File

@@ -25,3 +25,9 @@ func xgetbv() (eax, edx uint32) {
gccgoXgetbv(&a, &d)
return a, d
}
// gccgo doesn't build on Darwin, per:
// https://github.com/Homebrew/homebrew-core/blob/HEAD/Formula/gcc.rb#L76
func darwinSupportsAVX512() bool {
return false
}

10
cpu/cpu_x86.go
View File

@@ -87,8 +87,14 @@ func archInit() {
// Check if XMM and YMM registers have OS support.
osSupportsAVX = isSet(1, eax) && isSet(2, eax)
// Check if OPMASK and ZMM registers have OS support.
osSupportsAVX512 = osSupportsAVX && isSet(5, eax) && isSet(6, eax) && isSet(7, eax)
if runtime.GOOS == "darwin" {
// Check darwin commpage for AVX512 support. Necessary because:
// https://github.com/apple/darwin-xnu/blob/0a798f6738bc1db01281fc08ae024145e84df927/osfmk/i386/fpu.c#L175-L201
osSupportsAVX512 = osSupportsAVX && darwinSupportsAVX512()
} else {
// Check if OPMASK and ZMM registers have OS support.
osSupportsAVX512 = osSupportsAVX && isSet(5, eax) && isSet(6, eax) && isSet(7, eax)
}
}
X86.HasAVX = isSet(28, ecx1) && osSupportsAVX

24
cpu/cpu_x86.s
View File

@@ -26,3 +26,27 @@ TEXT ·xgetbv(SB),NOSPLIT,$0-8
MOVL AX, eax+0(FP)
MOVL DX, edx+4(FP)
RET
// func darwinSupportsAVX512() bool
TEXT ·darwinSupportsAVX512(SB), NOSPLIT, $0-1
MOVB $0, ret+0(FP) // default to false
#ifdef GOOS_darwin // return if not darwin
#ifdef GOARCH_amd64 // return if not amd64
// These values from:
// https://github.com/apple/darwin-xnu/blob/xnu-4570.1.46/osfmk/i386/cpu_capabilities.h
#define commpage64_base_address 0x00007fffffe00000
#define commpage64_cpu_capabilities64 (commpage64_base_address+0x010)
#define commpage64_version (commpage64_base_address+0x01E)
#define hasAVX512F 0x0000004000000000
MOVQ $commpage64_version, BX
CMPW (BX), $13 // cpu_capabilities64 undefined in versions < 13
JL no_avx512
MOVQ $commpage64_cpu_capabilities64, BX
MOVQ $hasAVX512F, CX
TESTQ (BX), CX
JZ no_avx512
MOVB $1, ret+0(FP)
no_avx512:
#endif
#endif
RET