From b6777538623b0f9036ec1234b8778c4877db489b Mon Sep 17 00:00:00 2001 From: Vaughn Iverson Date: Thu, 21 Jan 2021 16:49:49 -0800 Subject: [PATCH] cpu: fix AVX512 support detection on Darwin MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Run-TryBot: Tobias Klauser TryBot-Result: Go Bot Reviewed-by: Martin Möhrmann --- cpu/cpu_gc_x86.go | 4 ++++ cpu/cpu_gccgo_x86.go | 6 ++++++ cpu/cpu_x86.go | 10 ++++++++-- cpu/cpu_x86.s | 24 ++++++++++++++++++++++++ 4 files changed, 42 insertions(+), 2 deletions(-) diff --git a/cpu/cpu_gc_x86.go b/cpu/cpu_gc_x86.go index fa7cdb9b..3298a87e 100644 --- a/cpu/cpu_gc_x86.go +++ b/cpu/cpu_gc_x86.go @@ -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 diff --git a/cpu/cpu_gccgo_x86.go b/cpu/cpu_gccgo_x86.go index 8478a6d5..863d415a 100644 --- a/cpu/cpu_gccgo_x86.go +++ b/cpu/cpu_gccgo_x86.go @@ -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 +} diff --git a/cpu/cpu_x86.go b/cpu/cpu_x86.go index fd380c0a..54ca4667 100644 --- a/cpu/cpu_x86.go +++ b/cpu/cpu_x86.go @@ -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 diff --git a/cpu/cpu_x86.s b/cpu/cpu_x86.s index 39acab2f..b748ba52 100644 --- a/cpu/cpu_x86.s +++ b/cpu/cpu_x86.s @@ -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