src/internal/cpu/cpu_arm64.go

// 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 arm64

package cpu

const CacheLineSize = 64

// arm64 doesn't have a 'cpuid' equivalent, so we rely on HWCAP/HWCAP2.
// These are linknamed in runtime/os_linux_arm64.go and are initialized by
// archauxv().
var arm64_hwcap uint
var arm64_hwcap2 uint

// HWCAP/HWCAP2 bits. These are exposed by the kernel.
const (
        _ARM64_FEATURE_HAS_FP       = (1 << 0)
        _ARM64_FEATURE_HAS_ASIMD    = (1 << 1)
        _ARM64_FEATURE_HAS_EVTSTRM  = (1 << 2)
        _ARM64_FEATURE_HAS_AES      = (1 << 3)
        _ARM64_FEATURE_HAS_PMULL    = (1 << 4)
        _ARM64_FEATURE_HAS_SHA1     = (1 << 5)
        _ARM64_FEATURE_HAS_SHA2     = (1 << 6)
        _ARM64_FEATURE_HAS_CRC32    = (1 << 7)
        _ARM64_FEATURE_HAS_ATOMICS  = (1 << 8)
)

func init() {
	// HWCAP feature bits
	ARM64.HasFP       = isSet(arm64_hwcap, _ARM64_FEATURE_HAS_FP)
	ARM64.HasASIMD    = isSet(arm64_hwcap, _ARM64_FEATURE_HAS_ASIMD)
	ARM64.HasEVTSTRM  = isSet(arm64_hwcap, _ARM64_FEATURE_HAS_EVTSTRM)
	ARM64.HasAES      = isSet(arm64_hwcap, _ARM64_FEATURE_HAS_AES)
	ARM64.HasPMULL    = isSet(arm64_hwcap, _ARM64_FEATURE_HAS_PMULL)
	ARM64.HasSHA1     = isSet(arm64_hwcap, _ARM64_FEATURE_HAS_SHA1)
	ARM64.HasSHA2     = isSet(arm64_hwcap, _ARM64_FEATURE_HAS_SHA2)
	ARM64.HasCRC32    = isSet(arm64_hwcap, _ARM64_FEATURE_HAS_CRC32)
	ARM64.HasATOMICS  = isSet(arm64_hwcap, _ARM64_FEATURE_HAS_ATOMICS)
}

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