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// Copyright 2018 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.
// Package cpu implements processor feature detection for
// various CPU architectures.
package cpu
import (
"os"
"strings"
)
// Initialized reports whether the CPU features were initialized.
//
// For some GOOS/GOARCH combinations initialization of the CPU features depends
// on reading an operating specific file, e.g. /proc/self/auxv on linux/arm
// Initialized will report false if reading the file fails.
var Initialized bool
// CacheLinePad is used to pad structs to avoid false sharing.
type CacheLinePad struct{ _ [cacheLineSize]byte }
// X86 contains the supported CPU features of the
// current X86/AMD64 platform. If the current platform
// is not X86/AMD64 then all feature flags are false.
//
// X86 is padded to avoid false sharing. Further the HasAVX
// and HasAVX2 are only set if the OS supports XMM and YMM
// registers in addition to the CPUID feature bit being set.
var X86 struct {
_ CacheLinePad
HasAES bool // AES hardware implementation (AES NI)
HasADX bool // Multi-precision add-carry instruction extensions
HasAVX bool // Advanced vector extension
HasAVX2 bool // Advanced vector extension 2
HasAVX512 bool // Advanced vector extension 512
HasAVX512F bool // Advanced vector extension 512 Foundation Instructions
HasAVX512CD bool // Advanced vector extension 512 Conflict Detection Instructions
HasAVX512ER bool // Advanced vector extension 512 Exponential and Reciprocal Instructions
HasAVX512PF bool // Advanced vector extension 512 Prefetch Instructions Instructions
HasAVX512VL bool // Advanced vector extension 512 Vector Length Extensions
HasAVX512BW bool // Advanced vector extension 512 Byte and Word Instructions
HasAVX512DQ bool // Advanced vector extension 512 Doubleword and Quadword Instructions
HasAVX512IFMA bool // Advanced vector extension 512 Integer Fused Multiply Add
HasAVX512VBMI bool // Advanced vector extension 512 Vector Byte Manipulation Instructions
HasAVX5124VNNIW bool // Advanced vector extension 512 Vector Neural Network Instructions Word variable precision
HasAVX5124FMAPS bool // Advanced vector extension 512 Fused Multiply Accumulation Packed Single precision
HasAVX512VPOPCNTDQ bool // Advanced vector extension 512 Double and quad word population count instructions
HasAVX512VPCLMULQDQ bool // Advanced vector extension 512 Vector carry-less multiply operations
HasAVX512VNNI bool // Advanced vector extension 512 Vector Neural Network Instructions
HasAVX512GFNI bool // Advanced vector extension 512 Galois field New Instructions
HasAVX512VAES bool // Advanced vector extension 512 Vector AES instructions
HasAVX512VBMI2 bool // Advanced vector extension 512 Vector Byte Manipulation Instructions 2
HasAVX512BITALG bool // Advanced vector extension 512 Bit Algorithms
HasAVX512BF16 bool // Advanced vector extension 512 BFloat16 Instructions
HasBMI1 bool // Bit manipulation instruction set 1
HasBMI2 bool // Bit manipulation instruction set 2
HasCX16 bool // Compare and exchange 16 Bytes
HasERMS bool // Enhanced REP for MOVSB and STOSB
HasFMA bool // Fused-multiply-add instructions
HasOSXSAVE bool // OS supports XSAVE/XRESTOR for saving/restoring XMM registers.
HasPCLMULQDQ bool // PCLMULQDQ instruction - most often used for AES-GCM
HasPOPCNT bool // Hamming weight instruction POPCNT.
HasRDRAND bool // RDRAND instruction (on-chip random number generator)
HasRDSEED bool // RDSEED instruction (on-chip random number generator)
HasSSE2 bool // Streaming SIMD extension 2 (always available on amd64)
HasSSE3 bool // Streaming SIMD extension 3
HasSSSE3 bool // Supplemental streaming SIMD extension 3
HasSSE41 bool // Streaming SIMD extension 4 and 4.1
HasSSE42 bool // Streaming SIMD extension 4 and 4.2
_ CacheLinePad
}
// ARM64 contains the supported CPU features of the
// current ARMv8(aarch64) platform. If the current platform
// is not arm64 then all feature flags are false.
var ARM64 struct {
_ CacheLinePad
HasFP bool // Floating-point instruction set (always available)
HasASIMD bool // Advanced SIMD (always available)
HasEVTSTRM bool // Event stream support
HasAES bool // AES hardware implementation
HasPMULL bool // Polynomial multiplication instruction set
HasSHA1 bool // SHA1 hardware implementation
HasSHA2 bool // SHA2 hardware implementation
HasCRC32 bool // CRC32 hardware implementation
HasATOMICS bool // Atomic memory operation instruction set
HasFPHP bool // Half precision floating-point instruction set
HasASIMDHP bool // Advanced SIMD half precision instruction set
HasCPUID bool // CPUID identification scheme registers
HasASIMDRDM bool // Rounding double multiply add/subtract instruction set
HasJSCVT bool // Javascript conversion from floating-point to integer
HasFCMA bool // Floating-point multiplication and addition of complex numbers
HasLRCPC bool // Release Consistent processor consistent support
HasDCPOP bool // Persistent memory support
HasSHA3 bool // SHA3 hardware implementation
HasSM3 bool // SM3 hardware implementation
HasSM4 bool // SM4 hardware implementation
HasASIMDDP bool // Advanced SIMD double precision instruction set
HasSHA512 bool // SHA512 hardware implementation
HasSVE bool // Scalable Vector Extensions
HasASIMDFHM bool // Advanced SIMD multiplication FP16 to FP32
_ CacheLinePad
}
// ARM contains the supported CPU features of the current ARM (32-bit) platform.
// All feature flags are false if:
// 1. the current platform is not arm, or
// 2. the current operating system is not Linux.
var ARM struct {
_ CacheLinePad
HasSWP bool // SWP instruction support
HasHALF bool // Half-word load and store support
HasTHUMB bool // ARM Thumb instruction set
Has26BIT bool // Address space limited to 26-bits
HasFASTMUL bool // 32-bit operand, 64-bit result multiplication support
HasFPA bool // Floating point arithmetic support
HasVFP bool // Vector floating point support
HasEDSP bool // DSP Extensions support
HasJAVA bool // Java instruction set
HasIWMMXT bool // Intel Wireless MMX technology support
HasCRUNCH bool // MaverickCrunch context switching and handling
HasTHUMBEE bool // Thumb EE instruction set
HasNEON bool // NEON instruction set
HasVFPv3 bool // Vector floating point version 3 support
HasVFPv3D16 bool // Vector floating point version 3 D8-D15
HasTLS bool // Thread local storage support
HasVFPv4 bool // Vector floating point version 4 support
HasIDIVA bool // Integer divide instruction support in ARM mode
HasIDIVT bool // Integer divide instruction support in Thumb mode
HasVFPD32 bool // Vector floating point version 3 D15-D31
HasLPAE bool // Large Physical Address Extensions
HasEVTSTRM bool // Event stream support
HasAES bool // AES hardware implementation
HasPMULL bool // Polynomial multiplication instruction set
HasSHA1 bool // SHA1 hardware implementation
HasSHA2 bool // SHA2 hardware implementation
HasCRC32 bool // CRC32 hardware implementation
_ CacheLinePad
}
// MIPS64X contains the supported CPU features of the current mips64/mips64le
// platforms. If the current platform is not mips64/mips64le or the current
// operating system is not Linux then all feature flags are false.
var MIPS64X struct {
_ CacheLinePad
HasMSA bool // MIPS SIMD architecture
_ CacheLinePad
}
// PPC64 contains the supported CPU features of the current ppc64/ppc64le platforms.
// If the current platform is not ppc64/ppc64le then all feature flags are false.
//
// For ppc64/ppc64le, it is safe to check only for ISA level starting on ISA v3.00,
// since there are no optional categories. There are some exceptions that also
// require kernel support to work (DARN, SCV), so there are feature bits for
// those as well. The struct is padded to avoid false sharing.
var PPC64 struct {
_ CacheLinePad
HasDARN bool // Hardware random number generator (requires kernel enablement)
HasSCV bool // Syscall vectored (requires kernel enablement)
IsPOWER8 bool // ISA v2.07 (POWER8)
IsPOWER9 bool // ISA v3.00 (POWER9), implies IsPOWER8
_ CacheLinePad
}
// S390X contains the supported CPU features of the current IBM Z
// (s390x) platform. If the current platform is not IBM Z then all
// feature flags are false.
//
// S390X is padded to avoid false sharing. Further HasVX is only set
// if the OS supports vector registers in addition to the STFLE
// feature bit being set.
var S390X struct {
_ CacheLinePad
HasZARCH bool // z/Architecture mode is active [mandatory]
HasSTFLE bool // store facility list extended
HasLDISP bool // long (20-bit) displacements
HasEIMM bool // 32-bit immediates
HasDFP bool // decimal floating point
HasETF3EH bool // ETF-3 enhanced
HasMSA bool // message security assist (CPACF)
HasAES bool // KM-AES{128,192,256} functions
HasAESCBC bool // KMC-AES{128,192,256} functions
HasAESCTR bool // KMCTR-AES{128,192,256} functions
HasAESGCM bool // KMA-GCM-AES{128,192,256} functions
HasGHASH bool // KIMD-GHASH function
HasSHA1 bool // K{I,L}MD-SHA-1 functions
HasSHA256 bool // K{I,L}MD-SHA-256 functions
HasSHA512 bool // K{I,L}MD-SHA-512 functions
HasSHA3 bool // K{I,L}MD-SHA3-{224,256,384,512} and K{I,L}MD-SHAKE-{128,256} functions
HasVX bool // vector facility
HasVXE bool // vector-enhancements facility 1
_ CacheLinePad
}
func init() {
archInit()
initOptions()
processOptions()
}
// options contains the cpu debug options that can be used in GODEBUG.
// Options are arch dependent and are added by the arch specific initOptions functions.
// Features that are mandatory for the specific GOARCH should have the Required field set
// (e.g. SSE2 on amd64).
var options []option
// Option names should be lower case. e.g. avx instead of AVX.
type option struct {
Name string
Feature *bool
Specified bool // whether feature value was specified in GODEBUG
Enable bool // whether feature should be enabled
Required bool // whether feature is mandatory and can not be disabled
}
func processOptions() {
env := os.Getenv("GODEBUG")
field:
for env != "" {
field := ""
i := strings.IndexByte(env, ',')
if i < 0 {
field, env = env, ""
} else {
field, env = env[:i], env[i+1:]
}
if len(field) < 4 || field[:4] != "cpu." {
continue
}
i = strings.IndexByte(field, '=')
if i < 0 {
print("GODEBUG sys/cpu: no value specified for \"", field, "\"\n")
continue
}
key, value := field[4:i], field[i+1:] // e.g. "SSE2", "on"
var enable bool
switch value {
case "on":
enable = true
case "off":
enable = false
default:
print("GODEBUG sys/cpu: value \"", value, "\" not supported for cpu option \"", key, "\"\n")
continue field
}
if key == "all" {
for i := range options {
options[i].Specified = true
options[i].Enable = enable || options[i].Required
}
continue field
}
for i := range options {
if options[i].Name == key {
options[i].Specified = true
options[i].Enable = enable
continue field
}
}
print("GODEBUG sys/cpu: unknown cpu feature \"", key, "\"\n")
}
for _, o := range options {
if !o.Specified {
continue
}
if o.Enable && !*o.Feature {
print("GODEBUG sys/cpu: can not enable \"", o.Name, "\", missing CPU support\n")
continue
}
if !o.Enable && o.Required {
print("GODEBUG sys/cpu: can not disable \"", o.Name, "\", required CPU feature\n")
continue
}
*o.Feature = o.Enable
}
}
