221 lines
6.6 KiB
Go
221 lines
6.6 KiB
Go
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// Copyright 2017 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package cpu implements processor feature detection
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// used by the Go standard library.
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package cpu
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// DebugOptions is set to true by the runtime if the OS supports reading
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// GODEBUG early in runtime startup.
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// This should not be changed after it is initialized.
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var DebugOptions bool
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// CacheLinePad is used to pad structs to avoid false sharing.
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type CacheLinePad struct{ _ [CacheLinePadSize]byte }
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// CacheLineSize is the CPU's assumed cache line size.
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// There is currently no runtime detection of the real cache line size
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// so we use the constant per GOARCH CacheLinePadSize as an approximation.
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var CacheLineSize uintptr = CacheLinePadSize
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// The booleans in X86 contain the correspondingly named cpuid feature bit.
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// HasAVX and HasAVX2 are only set if the OS does support XMM and YMM registers
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// in addition to the cpuid feature bit being set.
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// The struct is padded to avoid false sharing.
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var X86 struct {
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_ CacheLinePad
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HasAES bool
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HasADX bool
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HasAVX bool
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HasAVX2 bool
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HasBMI1 bool
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HasBMI2 bool
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HasERMS bool
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HasFMA bool
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HasOSXSAVE bool
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HasPCLMULQDQ bool
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HasPOPCNT bool
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HasRDTSCP bool
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HasSSE3 bool
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HasSSSE3 bool
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HasSSE41 bool
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HasSSE42 bool
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_ CacheLinePad
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}
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// The booleans in ARM contain the correspondingly named cpu feature bit.
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// The struct is padded to avoid false sharing.
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var ARM struct {
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_ CacheLinePad
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HasVFPv4 bool
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HasIDIVA bool
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_ CacheLinePad
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}
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// The booleans in ARM64 contain the correspondingly named cpu feature bit.
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// The struct is padded to avoid false sharing.
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var ARM64 struct {
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_ CacheLinePad
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HasAES bool
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HasPMULL bool
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HasSHA1 bool
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HasSHA2 bool
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HasCRC32 bool
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HasATOMICS bool
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HasCPUID bool
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IsNeoverseN1 bool
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IsZeus bool
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_ CacheLinePad
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}
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var MIPS64X struct {
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_ CacheLinePad
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HasMSA bool // MIPS SIMD architecture
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_ CacheLinePad
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}
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// For ppc64(le), it is safe to check only for ISA level starting on ISA v3.00,
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// since there are no optional categories. There are some exceptions that also
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// require kernel support to work (darn, scv), so there are feature bits for
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// those as well. The minimum processor requirement is POWER8 (ISA 2.07).
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// The struct is padded to avoid false sharing.
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var PPC64 struct {
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_ CacheLinePad
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HasDARN bool // Hardware random number generator (requires kernel enablement)
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HasSCV bool // Syscall vectored (requires kernel enablement)
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IsPOWER8 bool // ISA v2.07 (POWER8)
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IsPOWER9 bool // ISA v3.00 (POWER9)
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_ CacheLinePad
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}
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var S390X struct {
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_ CacheLinePad
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HasZARCH bool // z architecture mode is active [mandatory]
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HasSTFLE bool // store facility list extended [mandatory]
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HasLDISP bool // long (20-bit) displacements [mandatory]
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HasEIMM bool // 32-bit immediates [mandatory]
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HasDFP bool // decimal floating point
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HasETF3EH bool // ETF-3 enhanced
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HasMSA bool // message security assist (CPACF)
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HasAES bool // KM-AES{128,192,256} functions
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HasAESCBC bool // KMC-AES{128,192,256} functions
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HasAESCTR bool // KMCTR-AES{128,192,256} functions
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HasAESGCM bool // KMA-GCM-AES{128,192,256} functions
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HasGHASH bool // KIMD-GHASH function
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HasSHA1 bool // K{I,L}MD-SHA-1 functions
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HasSHA256 bool // K{I,L}MD-SHA-256 functions
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HasSHA512 bool // K{I,L}MD-SHA-512 functions
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HasSHA3 bool // K{I,L}MD-SHA3-{224,256,384,512} and K{I,L}MD-SHAKE-{128,256} functions
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HasVX bool // vector facility. Note: the runtime sets this when it processes auxv records.
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HasVXE bool // vector-enhancements facility 1
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HasKDSA bool // elliptic curve functions
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HasECDSA bool // NIST curves
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HasEDDSA bool // Edwards curves
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_ CacheLinePad
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}
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// Initialize examines the processor and sets the relevant variables above.
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// This is called by the runtime package early in program initialization,
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// before normal init functions are run. env is set by runtime if the OS supports
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// cpu feature options in GODEBUG.
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func Initialize(env string) {
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doinit()
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processOptions(env)
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}
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// options contains the cpu debug options that can be used in GODEBUG.
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// Options are arch dependent and are added by the arch specific doinit functions.
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// Features that are mandatory for the specific GOARCH should not be added to options
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// (e.g. SSE2 on amd64).
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var options []option
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// Option names should be lower case. e.g. avx instead of AVX.
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type option struct {
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Name string
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Feature *bool
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Specified bool // whether feature value was specified in GODEBUG
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Enable bool // whether feature should be enabled
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}
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// processOptions enables or disables CPU feature values based on the parsed env string.
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// The env string is expected to be of the form cpu.feature1=value1,cpu.feature2=value2...
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// where feature names is one of the architecture specific list stored in the
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// cpu packages options variable and values are either 'on' or 'off'.
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// If env contains cpu.all=off then all cpu features referenced through the options
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// variable are disabled. Other feature names and values result in warning messages.
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func processOptions(env string) {
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field:
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for env != "" {
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field := ""
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i := indexByte(env, ',')
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if i < 0 {
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field, env = env, ""
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} else {
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field, env = env[:i], env[i+1:]
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}
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if len(field) < 4 || field[:4] != "cpu." {
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continue
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}
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i = indexByte(field, '=')
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if i < 0 {
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print("GODEBUG: no value specified for \"", field, "\"\n")
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continue
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}
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key, value := field[4:i], field[i+1:] // e.g. "SSE2", "on"
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var enable bool
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switch value {
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case "on":
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enable = true
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case "off":
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enable = false
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default:
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print("GODEBUG: value \"", value, "\" not supported for cpu option \"", key, "\"\n")
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continue field
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}
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if key == "all" {
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for i := range options {
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options[i].Specified = true
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options[i].Enable = enable
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}
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continue field
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}
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for i := range options {
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if options[i].Name == key {
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options[i].Specified = true
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options[i].Enable = enable
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continue field
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}
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}
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print("GODEBUG: unknown cpu feature \"", key, "\"\n")
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}
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for _, o := range options {
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if !o.Specified {
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continue
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}
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if o.Enable && !*o.Feature {
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print("GODEBUG: can not enable \"", o.Name, "\", missing CPU support\n")
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continue
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}
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*o.Feature = o.Enable
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}
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}
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// indexByte returns the index of the first instance of c in s,
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// or -1 if c is not present in s.
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func indexByte(s string, c byte) int {
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for i := 0; i < len(s); i++ {
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if s[i] == c {
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return i
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}
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}
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return -1
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}
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