Documentation
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Overview ¶
Package cpu implements processor feature detection used by the Go standard library.
Index ¶
Constants ¶
const CacheLinePadSize = 64
Variables ¶
var ARM struct { HasVFPv4 bool HasIDIVA bool HasV7Atomics bool // contains filtered or unexported fields }
The booleans in ARM contain the correspondingly named cpu feature bit. The struct is padded to avoid false sharing.
var ARM64 struct { HasAES bool HasPMULL bool HasSHA1 bool HasSHA2 bool HasSHA512 bool HasCRC32 bool HasATOMICS bool HasCPUID bool IsNeoverse bool // contains filtered or unexported fields }
The booleans in ARM64 contain the correspondingly named cpu feature bit. The struct is padded to avoid false sharing.
var CacheLineSize uintptr = CacheLinePadSize
CacheLineSize is the CPU's assumed cache line size. There is currently no runtime detection of the real cache line size so we use the constant per GOARCH CacheLinePadSize as an approximation.
var DebugOptions bool
DebugOptions is set to true by the runtime if the OS supports reading GODEBUG early in runtime startup. This should not be changed after it is initialized.
var MIPS64X struct { HasMSA bool // MIPS SIMD architecture // contains filtered or unexported fields }
var PPC64 struct { 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) IsPOWER10 bool // ISA v3.1 (POWER10) // contains filtered or unexported fields }
For ppc64(le), 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 minimum processor requirement is POWER8 (ISA 2.07). The struct is padded to avoid false sharing.
var S390X struct { HasZARCH bool // z architecture mode is active [mandatory] HasSTFLE bool // store facility list extended [mandatory] HasLDISP bool // long (20-bit) displacements [mandatory] HasEIMM bool // 32-bit immediates [mandatory] 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. Note: the runtime sets this when it processes auxv records. HasVXE bool // vector-enhancements facility 1 HasKDSA bool // elliptic curve functions HasECDSA bool // NIST curves HasEDDSA bool // Edwards curves // contains filtered or unexported fields }
var X86 struct { HasAES bool HasADX bool HasAVX bool HasAVX2 bool HasAVX512F bool HasAVX512BW bool HasAVX512VL bool HasBMI1 bool HasBMI2 bool HasERMS bool HasFMA bool HasOSXSAVE bool HasPCLMULQDQ bool HasPOPCNT bool HasRDTSCP bool HasSHA bool HasSSE3 bool HasSSSE3 bool HasSSE41 bool HasSSE42 bool // contains filtered or unexported fields }
The booleans in X86 contain the correspondingly named cpuid feature bit. HasAVX and HasAVX2 are only set if the OS does support XMM and YMM registers in addition to the cpuid feature bit being set. The struct is padded to avoid false sharing.
Functions ¶
func Initialize ¶ added in go1.12
func Initialize(env string)
Initialize examines the processor and sets the relevant variables above. This is called by the runtime package early in program initialization, before normal init functions are run. env is set by runtime if the OS supports cpu feature options in GODEBUG.
Types ¶
type CacheLinePad ¶ added in go1.12
type CacheLinePad struct {
// contains filtered or unexported fields
}
CacheLinePad is used to pad structs to avoid false sharing.
Source Files