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Source file src/internal/cpu/cpu_x86.go

Documentation: internal/cpu

  // 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.
  
  // +build 386 amd64 amd64p32
  
  package cpu
  
  const CacheLineSize = 64
  
  // cpuid is implemented in cpu_x86.s.
  func cpuid(eaxArg, ecxArg uint32) (eax, ebx, ecx, edx uint32)
  
  // xgetbv with ecx = 0 is implemented in cpu_x86.s.
  func xgetbv() (eax, edx uint32)
  
  func init() {
  	maxId, _, _, _ := cpuid(0, 0)
  
  	if maxId < 1 {
  		return
  	}
  
  	_, _, ecx1, edx1 := cpuid(1, 0)
  	X86.HasSSE2 = isSet(26, edx1)
  
  	X86.HasSSE3 = isSet(0, ecx1)
  	X86.HasPCLMULQDQ = isSet(1, ecx1)
  	X86.HasSSSE3 = isSet(9, ecx1)
  	X86.HasSSE41 = isSet(19, ecx1)
  	X86.HasSSE42 = isSet(20, ecx1)
  	X86.HasPOPCNT = isSet(23, ecx1)
  	X86.HasAES = isSet(25, ecx1)
  	X86.HasOSXSAVE = isSet(27, ecx1)
  
  	osSupportsAVX := false
  	// For XGETBV, OSXSAVE bit is required and sufficient.
  	if X86.HasOSXSAVE {
  		eax, _ := xgetbv()
  		// Check if XMM and YMM registers have OS support.
  		osSupportsAVX = isSet(1, eax) && isSet(2, eax)
  	}
  
  	X86.HasAVX = isSet(28, ecx1) && osSupportsAVX
  
  	if maxId < 7 {
  		return
  	}
  
  	_, ebx7, _, _ := cpuid(7, 0)
  	X86.HasBMI1 = isSet(3, ebx7)
  	X86.HasAVX2 = isSet(5, ebx7) && osSupportsAVX
  	X86.HasBMI2 = isSet(8, ebx7)
  	X86.HasERMS = isSet(9, ebx7)
  }
  
  func isSet(bitpos uint, value uint32) bool {
  	return value&(1<<bitpos) != 0
  }
  

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