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Diffstat (limited to 'src/internal/cpu/cpu.go')
| -rw-r--r-- | src/internal/cpu/cpu.go | 226 |
1 files changed, 226 insertions, 0 deletions
diff --git a/src/internal/cpu/cpu.go b/src/internal/cpu/cpu.go new file mode 100644 index 0000000..dab5d06 --- /dev/null +++ b/src/internal/cpu/cpu.go @@ -0,0 +1,226 @@ +// 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. + +// Package cpu implements processor feature detection +// used by the Go standard library. +package cpu + +// 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 DebugOptions bool + +// CacheLinePad is used to pad structs to avoid false sharing. +type CacheLinePad struct{ _ [CacheLinePadSize]byte } + +// 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 CacheLineSize uintptr = CacheLinePadSize + +// 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. +var X86 struct { + _ CacheLinePad + HasAES bool + HasADX bool + HasAVX bool + HasAVX2 bool + HasBMI1 bool + HasBMI2 bool + HasERMS bool + HasFMA bool + HasOSXSAVE bool + HasPCLMULQDQ bool + HasPOPCNT bool + HasSSE2 bool + HasSSE3 bool + HasSSSE3 bool + HasSSE41 bool + HasSSE42 bool + _ CacheLinePad +} + +// The booleans in ARM contain the correspondingly named cpu feature bit. +// The struct is padded to avoid false sharing. +var ARM struct { + _ CacheLinePad + HasVFPv4 bool + HasIDIVA bool + _ CacheLinePad +} + +// The booleans in ARM64 contain the correspondingly named cpu feature bit. +// The struct is padded to avoid false sharing. +var ARM64 struct { + _ CacheLinePad + HasAES bool + HasPMULL bool + HasSHA1 bool + HasSHA2 bool + HasCRC32 bool + HasATOMICS bool + HasCPUID bool + IsNeoverseN1 bool + IsZeus bool + _ CacheLinePad +} + +var MIPS64X struct { + _ CacheLinePad + HasMSA bool // MIPS SIMD architecture + _ CacheLinePad +} + +// 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 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) + _ CacheLinePad +} + +var S390X struct { + _ CacheLinePad + 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 + _ CacheLinePad +} + +// 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. +func Initialize(env string) { + doinit() + processOptions(env) +} + +// options contains the cpu debug options that can be used in GODEBUG. +// Options are arch dependent and are added by the arch specific doinit functions. +// Features that are mandatory for the specific GOARCH should not be added to options +// (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 +} + +// processOptions enables or disables CPU feature values based on the parsed env string. +// The env string is expected to be of the form cpu.feature1=value1,cpu.feature2=value2... +// where feature names is one of the architecture specific list stored in the +// cpu packages options variable and values are either 'on' or 'off'. +// If env contains cpu.all=off then all cpu features referenced through the options +// variable are disabled. Other feature names and values result in warning messages. +func processOptions(env string) { +field: + for env != "" { + field := "" + i := 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 = indexByte(field, '=') + if i < 0 { + print("GODEBUG: 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: 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: unknown cpu feature \"", key, "\"\n") + } + + for _, o := range options { + if !o.Specified { + continue + } + + if o.Enable && !*o.Feature { + print("GODEBUG: can not enable \"", o.Name, "\", missing CPU support\n") + continue + } + + if !o.Enable && o.Required { + print("GODEBUG: can not disable \"", o.Name, "\", required CPU feature\n") + continue + } + + *o.Feature = o.Enable + } +} + +// indexByte returns the index of the first instance of c in s, +// or -1 if c is not present in s. +func indexByte(s string, c byte) int { + for i := 0; i < len(s); i++ { + if s[i] == c { + return i + } + } + return -1 +} |