tzhash/internal/cpuid/cpuid_x86.go

// Copyright (c) 2009 The Go Authors. All rights reserved.
//
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// modification, are permitted provided that the following conditions are
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//
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// in the documentation and/or other materials provided with the
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// +build 386 amd64 amd64p32

package cpuid

const (
	bitOSXSAVE = 1 << 27
	bitAVX     = 1 << 28
	bitAVX2    = 1 << 5
)

var (
	hasAVX  bool
	hasAVX2 bool
)

func init() {
	maxID, _, _, _ := cpuid(0, 0)
	if maxID < 1 {
		return
	}

	_, _, ecx1, _ := cpuid(1, 0)
	hasOSXSAVE := isSet(ecx1, bitOSXSAVE)

	osSupportsAVX := false
	if hasOSXSAVE {
		eax, _ := xgetbv()
		osSupportsAVX = isSet(eax, 1<<1) && isSet(eax, 1<<2)
	}

	hasAVX = isSet(ecx1, bitAVX) && osSupportsAVX

	if maxID < 7 {
		return
	}

	_, ebx7, _, _ := cpuid(7, 0)
	hasAVX2 = isSet(ebx7, bitAVX2) && osSupportsAVX
}

func HasAVX() bool  { return hasAVX }
func HasAVX2() bool { return hasAVX2 }

func isSet(hwc uint32, value uint32) bool {
	return hwc&value != 0
}

func cpuid(eaxArg, ecxArg uint32) (eax, ebx, ecx, edx uint32)
func xgetbv() (eax, edx uint32)