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| 1 | +// Copyright 2017 The Go Authors. All rights reserved. |
| 2 | +// Use of this source code is governed by a BSD-style |
| 3 | +// license that can be found in the LICENSE file. |
| 4 | + |
| 5 | +// Package cpu implements processor feature detection |
| 6 | +// used by the Go standard library. |
| 7 | +package cpu |
| 8 | + |
| 9 | +import _ "unsafe" // for linkname |
| 10 | + |
| 11 | +// DebugOptions is set to true by the runtime if the OS supports reading |
| 12 | +// GODEBUG early in runtime startup. |
| 13 | +// This should not be changed after it is initialized. |
| 14 | +var DebugOptions bool |
| 15 | + |
| 16 | +// CacheLinePad is used to pad structs to avoid false sharing. |
| 17 | +type CacheLinePad struct{ _ [CacheLinePadSize]byte } |
| 18 | + |
| 19 | +// CacheLineSize is the CPU's assumed cache line size. |
| 20 | +// There is currently no runtime detection of the real cache line size |
| 21 | +// so we use the constant per GOARCH CacheLinePadSize as an approximation. |
| 22 | +var CacheLineSize uintptr = CacheLinePadSize |
| 23 | + |
| 24 | +// The booleans in X86 contain the correspondingly named cpuid feature bit. |
| 25 | +// HasAVX and HasAVX2 are only set if the OS does support XMM and YMM registers |
| 26 | +// in addition to the cpuid feature bit being set. |
| 27 | +// The struct is padded to avoid false sharing. |
| 28 | +var X86 struct { |
| 29 | + _ CacheLinePad |
| 30 | + HasAES bool |
| 31 | + HasADX bool |
| 32 | + HasAVX bool |
| 33 | + HasAVX2 bool |
| 34 | + HasAVX512F bool |
| 35 | + HasAVX512BW bool |
| 36 | + HasAVX512VL bool |
| 37 | + HasBMI1 bool |
| 38 | + HasBMI2 bool |
| 39 | + HasERMS bool |
| 40 | + HasFSRM bool |
| 41 | + HasFMA bool |
| 42 | + HasOSXSAVE bool |
| 43 | + HasPCLMULQDQ bool |
| 44 | + HasPOPCNT bool |
| 45 | + HasRDTSCP bool |
| 46 | + HasSHA bool |
| 47 | + HasSSE3 bool |
| 48 | + HasSSSE3 bool |
| 49 | + HasSSE41 bool |
| 50 | + HasSSE42 bool |
| 51 | + _ CacheLinePad |
| 52 | +} |
| 53 | + |
| 54 | +// The booleans in ARM contain the correspondingly named cpu feature bit. |
| 55 | +// The struct is padded to avoid false sharing. |
| 56 | +var ARM struct { |
| 57 | + _ CacheLinePad |
| 58 | + HasVFPv4 bool |
| 59 | + HasIDIVA bool |
| 60 | + HasV7Atomics bool |
| 61 | + _ CacheLinePad |
| 62 | +} |
| 63 | + |
| 64 | +// The booleans in ARM64 contain the correspondingly named cpu feature bit. |
| 65 | +// The struct is padded to avoid false sharing. |
| 66 | +var ARM64 struct { |
| 67 | + _ CacheLinePad |
| 68 | + HasAES bool |
| 69 | + HasPMULL bool |
| 70 | + HasSHA1 bool |
| 71 | + HasSHA2 bool |
| 72 | + HasSHA512 bool |
| 73 | + HasSHA3 bool |
| 74 | + HasCRC32 bool |
| 75 | + HasATOMICS bool |
| 76 | + HasCPUID bool |
| 77 | + HasDIT bool |
| 78 | + IsNeoverse bool |
| 79 | + _ CacheLinePad |
| 80 | +} |
| 81 | + |
| 82 | +// The booleans in Loong64 contain the correspondingly named cpu feature bit. |
| 83 | +// The struct is padded to avoid false sharing. |
| 84 | +var Loong64 struct { |
| 85 | + _ CacheLinePad |
| 86 | + HasLSX bool // support 128-bit vector extension |
| 87 | + HasLASX bool // support 256-bit vector extension |
| 88 | + HasCRC32 bool // support CRC instruction |
| 89 | + HasLAMCAS bool // support AMCAS[_DB].{B/H/W/D} |
| 90 | + HasLAM_BH bool // support AM{SWAP/ADD}[_DB].{B/H} instruction |
| 91 | + _ CacheLinePad |
| 92 | +} |
| 93 | + |
| 94 | +var MIPS64X struct { |
| 95 | + _ CacheLinePad |
| 96 | + HasMSA bool // MIPS SIMD architecture |
| 97 | + _ CacheLinePad |
| 98 | +} |
| 99 | + |
| 100 | +// For ppc64(le), it is safe to check only for ISA level starting on ISA v3.00, |
| 101 | +// since there are no optional categories. There are some exceptions that also |
| 102 | +// require kernel support to work (darn, scv), so there are feature bits for |
| 103 | +// those as well. The minimum processor requirement is POWER8 (ISA 2.07). |
| 104 | +// The struct is padded to avoid false sharing. |
| 105 | +var PPC64 struct { |
| 106 | + _ CacheLinePad |
| 107 | + HasDARN bool // Hardware random number generator (requires kernel enablement) |
| 108 | + HasSCV bool // Syscall vectored (requires kernel enablement) |
| 109 | + IsPOWER8 bool // ISA v2.07 (POWER8) |
| 110 | + IsPOWER9 bool // ISA v3.00 (POWER9) |
| 111 | + IsPOWER10 bool // ISA v3.1 (POWER10) |
| 112 | + _ CacheLinePad |
| 113 | +} |
| 114 | + |
| 115 | +var S390X struct { |
| 116 | + _ CacheLinePad |
| 117 | + HasZARCH bool // z architecture mode is active [mandatory] |
| 118 | + HasSTFLE bool // store facility list extended [mandatory] |
| 119 | + HasLDISP bool // long (20-bit) displacements [mandatory] |
| 120 | + HasEIMM bool // 32-bit immediates [mandatory] |
| 121 | + HasDFP bool // decimal floating point |
| 122 | + HasETF3EH bool // ETF-3 enhanced |
| 123 | + HasMSA bool // message security assist (CPACF) |
| 124 | + HasAES bool // KM-AES{128,192,256} functions |
| 125 | + HasAESCBC bool // KMC-AES{128,192,256} functions |
| 126 | + HasAESCTR bool // KMCTR-AES{128,192,256} functions |
| 127 | + HasAESGCM bool // KMA-GCM-AES{128,192,256} functions |
| 128 | + HasGHASH bool // KIMD-GHASH function |
| 129 | + HasSHA1 bool // K{I,L}MD-SHA-1 functions |
| 130 | + HasSHA256 bool // K{I,L}MD-SHA-256 functions |
| 131 | + HasSHA512 bool // K{I,L}MD-SHA-512 functions |
| 132 | + HasSHA3 bool // K{I,L}MD-SHA3-{224,256,384,512} and K{I,L}MD-SHAKE-{128,256} functions |
| 133 | + HasVX bool // vector facility. Note: the runtime sets this when it processes auxv records. |
| 134 | + HasVXE bool // vector-enhancements facility 1 |
| 135 | + HasKDSA bool // elliptic curve functions |
| 136 | + HasECDSA bool // NIST curves |
| 137 | + HasEDDSA bool // Edwards curves |
| 138 | + _ CacheLinePad |
| 139 | +} |
| 140 | + |
| 141 | +// RISCV64 contains the supported CPU features and performance characteristics for riscv64 |
| 142 | +// platforms. The booleans in RISCV64, with the exception of HasFastMisaligned, indicate |
| 143 | +// the presence of RISC-V extensions. |
| 144 | +// The struct is padded to avoid false sharing. |
| 145 | +var RISCV64 struct { |
| 146 | + _ CacheLinePad |
| 147 | + HasFastMisaligned bool // Fast misaligned accesses |
| 148 | + HasV bool // Vector extension compatible with RVV 1.0 |
| 149 | + HasZbb bool // Basic bit-manipulation extension |
| 150 | + _ CacheLinePad |
| 151 | +} |
| 152 | + |
| 153 | +// CPU feature variables are accessed by assembly code in various packages. |
| 154 | +//go:linkname X86 |
| 155 | +//go:linkname ARM |
| 156 | +//go:linkname ARM64 |
| 157 | +//go:linkname Loong64 |
| 158 | +//go:linkname MIPS64X |
| 159 | +//go:linkname PPC64 |
| 160 | +//go:linkname S390X |
| 161 | +//go:linkname RISCV64 |
| 162 | + |
| 163 | +// Initialize examines the processor and sets the relevant variables above. |
| 164 | +// This is called by the runtime package early in program initialization, |
| 165 | +// before normal init functions are run. env is set by runtime if the OS supports |
| 166 | +// cpu feature options in GODEBUG. |
| 167 | +func Initialize(env string) { |
| 168 | + doinit() |
| 169 | + processOptions(env) |
| 170 | +} |
| 171 | + |
| 172 | +// options contains the cpu debug options that can be used in GODEBUG. |
| 173 | +// Options are arch dependent and are added by the arch specific doinit functions. |
| 174 | +// Features that are mandatory for the specific GOARCH should not be added to options |
| 175 | +// (e.g. SSE2 on amd64). |
| 176 | +var options []option |
| 177 | + |
| 178 | +// Option names should be lower case. e.g. avx instead of AVX. |
| 179 | +type option struct { |
| 180 | + Name string |
| 181 | + Feature *bool |
| 182 | + Specified bool // whether feature value was specified in GODEBUG |
| 183 | + Enable bool // whether feature should be enabled |
| 184 | +} |
| 185 | + |
| 186 | +// processOptions enables or disables CPU feature values based on the parsed env string. |
| 187 | +// The env string is expected to be of the form cpu.feature1=value1,cpu.feature2=value2... |
| 188 | +// where feature names is one of the architecture specific list stored in the |
| 189 | +// cpu packages options variable and values are either 'on' or 'off'. |
| 190 | +// If env contains cpu.all=off then all cpu features referenced through the options |
| 191 | +// variable are disabled. Other feature names and values result in warning messages. |
| 192 | +func processOptions(env string) { |
| 193 | +field: |
| 194 | + for env != "" { |
| 195 | + field := "" |
| 196 | + i := indexByte(env, ',') |
| 197 | + if i < 0 { |
| 198 | + field, env = env, "" |
| 199 | + } else { |
| 200 | + field, env = env[:i], env[i+1:] |
| 201 | + } |
| 202 | + if len(field) < 4 || field[:4] != "cpu." { |
| 203 | + continue |
| 204 | + } |
| 205 | + i = indexByte(field, '=') |
| 206 | + if i < 0 { |
| 207 | + print("GODEBUG: no value specified for \"", field, "\"\n") |
| 208 | + continue |
| 209 | + } |
| 210 | + key, value := field[4:i], field[i+1:] // e.g. "SSE2", "on" |
| 211 | + |
| 212 | + var enable bool |
| 213 | + switch value { |
| 214 | + case "on": |
| 215 | + enable = true |
| 216 | + case "off": |
| 217 | + enable = false |
| 218 | + default: |
| 219 | + print("GODEBUG: value \"", value, "\" not supported for cpu option \"", key, "\"\n") |
| 220 | + continue field |
| 221 | + } |
| 222 | + |
| 223 | + if key == "all" { |
| 224 | + for i := range options { |
| 225 | + options[i].Specified = true |
| 226 | + options[i].Enable = enable |
| 227 | + } |
| 228 | + continue field |
| 229 | + } |
| 230 | + |
| 231 | + for i := range options { |
| 232 | + if options[i].Name == key { |
| 233 | + options[i].Specified = true |
| 234 | + options[i].Enable = enable |
| 235 | + continue field |
| 236 | + } |
| 237 | + } |
| 238 | + |
| 239 | + print("GODEBUG: unknown cpu feature \"", key, "\"\n") |
| 240 | + } |
| 241 | + |
| 242 | + for _, o := range options { |
| 243 | + if !o.Specified { |
| 244 | + continue |
| 245 | + } |
| 246 | + |
| 247 | + if o.Enable && !*o.Feature { |
| 248 | + print("GODEBUG: can not enable \"", o.Name, "\", missing CPU support\n") |
| 249 | + continue |
| 250 | + } |
| 251 | + |
| 252 | + *o.Feature = o.Enable |
| 253 | + } |
| 254 | +} |
| 255 | + |
| 256 | +// indexByte returns the index of the first instance of c in s, |
| 257 | +// or -1 if c is not present in s. |
| 258 | +// indexByte is semantically the same as [strings.IndexByte]. |
| 259 | +// We copy this function because "internal/cpu" should not have external dependencies. |
| 260 | +func indexByte(s string, c byte) int { |
| 261 | + for i := 0; i < len(s); i++ { |
| 262 | + if s[i] == c { |
| 263 | + return i |
| 264 | + } |
| 265 | + } |
| 266 | + return -1 |
| 267 | +} |
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