golang cpu_arm64_freebsd 代码
文件路径：/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.
/go: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)
}