src/internal/cpu/cpu_arm64_freebsd.go

// Copyright 2020 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

func osInit() {
	// Retrieve info from system register ID_AA64ISAR0_EL1.
	isar0 := getisar0()

	// ID_AA64ISAR0_EL1
	switch extractBits(isar0, 4, 7) {
	case 1:
		ARM64.HasAES = true
	case 2:
		ARM64.HasAES = true
		ARM64.HasPMULL = true
	}

	switch extractBits(isar0, 8, 11) {
	case 1:
		ARM64.HasSHA1 = true
	}

	switch extractBits(isar0, 12, 15) {
	case 1, 2:
		ARM64.HasSHA2 = true
	}

	switch extractBits(isar0, 16, 19) {
	case 1:
		ARM64.HasCRC32 = true
	}

	switch extractBits(isar0, 20, 23) {
	case 2:
		ARM64.HasATOMICS = true
	}
}

func extractBits(data uint64, start, end uint) uint {
	return (uint)(data>>start) & ((1 << (end - start + 1)) - 1)
}