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darwin/arm64: fix SIMD detection and improve ARM feature probing (#160)
* darwin/arm64: fix SIMD detection and improve ARM feature probing Detection of Advanced SIMD (NEON) on M1 Macs was broken due to querying the wrong sysctl identifier. Apple's documentation lists "hw.optional.AdvSIMD" as the correct identifier, but in reality, it's "hw.optional.arm.AdvSIMD" as confirmed by `sysctl -a`. This patch corrects the identifier and adds support for its alias, "hw.optional .neon," ensuring proper detection across all models. Additionally, this patch revisits all ARM features detected by the package, cross-referencing identifiers (and aliases) against both Apple's official sysctl documentation: https://developer.apple.com/documentation/kernel/1387446-sysctlbyname/determining_instruction_set_characteristics and the ARM architecture reference manual: https://developer.arm.com/documentation/ddi0487/latest Each ARM feature now maps to all known sysctl aliases, preventing false negatives and improving detection accuracy on Apple Silicon. * nit * fix typo
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2 files changed

Lines changed: 42 additions & 40 deletions

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‎cpuid.go‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -286,7 +286,7 @@ const (
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CRC32 // CRC32/CRC32C instructions
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DCPOP // Data cache clean to Point of Persistence (DC CVAP)
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EVTSTRM // Generic timer
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FCMA // Floatin point complex number addition and multiplication
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FCMA // Floating point complex number addition and multiplication
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FHM // FMLAL and FMLSL instructions
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FP // Single-precision and double-precision floating point
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FPHP // Half-precision floating point

‎os_darwin_arm64.go‎

Lines changed: 41 additions & 39 deletions
Original file line numberDiff line numberDiff line change
@@ -65,9 +65,16 @@ func sysctlGetInt64(unknown int, names ...string) int {
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return unknown
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}
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68-
func setFeature(c *CPUInfo, name string, feature FeatureID) {
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c.featureSet.setIf(sysctlGetBool(name), feature)
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func setFeature(c *CPUInfo, feature FeatureID, aliases ...string) {
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for _, alias := range aliases {
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set := sysctlGetBool(alias)
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c.featureSet.setIf(set, feature)
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if set {
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break
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}
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}
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}
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func tryToFillCPUInfoFomSysctl(c *CPUInfo) {
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c.BrandName = sysctlGetString("machdep.cpu.brand_string")
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@@ -87,41 +94,36 @@ func tryToFillCPUInfoFomSysctl(c *CPUInfo) {
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c.Cache.L2 = sysctlGetInt64(-1, "hw.l2cachesize")
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c.Cache.L3 = sysctlGetInt64(-1, "hw.l3cachesize")
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// from https://developer.arm.com/downloads/-/exploration-tools/feature-names-for-a-profile
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setFeature(c, "hw.optional.arm.FEAT_AES", AESARM)
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setFeature(c, "hw.optional.AdvSIMD", ASIMD)
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setFeature(c, "hw.optional.arm.FEAT_DotProd", ASIMDDP)
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setFeature(c, "hw.optional.arm.FEAT_RDM", ASIMDRDM)
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setFeature(c, "hw.optional.FEAT_CRC32", CRC32)
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setFeature(c, "hw.optional.arm.FEAT_DPB", DCPOP)
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// setFeature(c, "", EVTSTRM)
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setFeature(c, "hw.optional.arm.FEAT_FCMA", FCMA)
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setFeature(c, "hw.optional.arm.FEAT_FHM", FHM)
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setFeature(c, "hw.optional.arm.FEAT_FP", FP)
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setFeature(c, "hw.optional.arm.FEAT_FP16", FPHP)
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setFeature(c, "hw.optional.arm.FEAT_PAuth", GPA)
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setFeature(c, "hw.optional.arm.FEAT_RNG", RNDR)
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setFeature(c, "hw.optional.arm.FEAT_JSCVT", JSCVT)
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setFeature(c, "hw.optional.arm.FEAT_LRCPC", LRCPC)
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setFeature(c, "hw.optional.arm.FEAT_PMULL", PMULL)
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setFeature(c, "hw.optional.arm.FEAT_SHA1", SHA1)
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setFeature(c, "hw.optional.arm.FEAT_SHA256", SHA2)
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setFeature(c, "hw.optional.arm.FEAT_SHA3", SHA3)
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setFeature(c, "hw.optional.arm.FEAT_SHA512", SHA512)
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setFeature(c, "hw.optional.arm.FEAT_TLBIOS", TLB)
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setFeature(c, "hw.optional.arm.FEAT_TLBIRANGE", TLB)
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setFeature(c, "hw.optional.arm.FEAT_FlagM", TS)
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setFeature(c, "hw.optional.arm.FEAT_FlagM2", TS)
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// setFeature(c, "", SM3)
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// setFeature(c, "", SM4)
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setFeature(c, "hw.optional.arm.FEAT_SVE", SVE)
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// from empirical observation
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setFeature(c, "hw.optional.AdvSIMD_HPFPCvt", ASIMDHP)
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setFeature(c, "hw.optional.armv8_1_atomics", ATOMICS)
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setFeature(c, "hw.optional.floatingpoint", FP)
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setFeature(c, "hw.optional.armv8_2_sha3", SHA3)
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setFeature(c, "hw.optional.armv8_2_sha512", SHA512)
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setFeature(c, "hw.optional.armv8_3_compnum", FCMA)
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setFeature(c, "hw.optional.armv8_crc32", CRC32)
97+
// ARM features:
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//
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// Note: On some Apple Silicon system, some feats have aliases. See:
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// https://developer.apple.com/documentation/kernel/1387446-sysctlbyname/determining_instruction_set_characteristics
101+
// When so, we look at all aliases and consider a feature available when at least one identifier matches.
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setFeature(c, AESARM, "hw.optional.arm.FEAT_AES") // AES instructions
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setFeature(c, ASIMD, "hw.optional.arm.AdvSIMD", "hw.optional.neon") // Advanced SIMD
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setFeature(c, ASIMDDP, "hw.optional.arm.FEAT_DotProd") // SIMD Dot Product
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setFeature(c, ASIMDHP, "hw.optional.arm.AdvSIMD_HPFPCvt", "hw.optional.neon_hpfp") // Advanced SIMD half-precision floating point
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setFeature(c, ASIMDRDM, "hw.optional.arm.FEAT_RDM") // Rounding Double Multiply Accumulate/Subtract
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setFeature(c, ATOMICS, "hw.optional.arm.FEAT_LSE", "hw.optional.armv8_1_atomics") // Large System Extensions (LSE)
108+
setFeature(c, CRC32, "hw.optional.arm.FEAT_CRC32", "hw.optional.armv8_crc32") // CRC32/CRC32C instructions
109+
setFeature(c, DCPOP, "hw.optional.arm.FEAT_DPB") // Data cache clean to Point of Persistence (DC CVAP)
110+
setFeature(c, EVTSTRM, "hw.optional.arm.FEAT_ECV") // Generic timer
111+
setFeature(c, FCMA, "hw.optional.arm.FEAT_FCMA", "hw.optional.armv8_3_compnum") // Floating point complex number addition and multiplication
112+
setFeature(c, FHM, "hw.optional.armv8_2_fhm", "hw.optional.arm.FEAT_FHM") // FMLAL and FMLSL instructions
113+
setFeature(c, FP, "hw.optional.floatingpoint") // Single-precision and double-precision floating point
114+
setFeature(c, FPHP, "hw.optional.arm.FEAT_FP16", "hw.optional.neon_fp16") // Half-precision floating point
115+
setFeature(c, GPA, "hw.optional.arm.FEAT_PAuth") // Generic Pointer Authentication
116+
setFeature(c, JSCVT, "hw.optional.arm.FEAT_JSCVT") // Javascript-style double->int convert (FJCVTZS)
117+
setFeature(c, LRCPC, "hw.optional.arm.FEAT_LRCPC") // Weaker release consistency (LDAPR, etc)
118+
setFeature(c, PMULL, "hw.optional.arm.FEAT_PMULL") // Polynomial Multiply instructions (PMULL/PMULL2)
119+
setFeature(c, RNDR, "hw.optional.arm.FEAT_RNG") // Random Number instructions
120+
setFeature(c, TLB, "hw.optional.arm.FEAT_TLBIOS", "hw.optional.arm.FEAT_TLBIRANGE") // Outer Shareable and TLB range maintenance instructions
121+
setFeature(c, TS, "hw.optional.arm.FEAT_FlagM", "hw.optional.arm.FEAT_FlagM2") // Flag manipulation instructions
122+
setFeature(c, SHA1, "hw.optional.arm.FEAT_SHA1") // SHA-1 instructions (SHA1C, etc)
123+
setFeature(c, SHA2, "hw.optional.arm.FEAT_SHA256") // SHA-2 instructions (SHA256H, etc)
124+
setFeature(c, SHA3, "hw.optional.arm.FEAT_SHA3") // SHA-3 instructions (EOR3, RAXI, XAR, BCAX)
125+
setFeature(c, SHA512, "hw.optional.arm.FEAT_SHA512") // SHA512 instructions
126+
setFeature(c, SM3, "hw.optional.arm.FEAT_SM3") // SM3 instructions
127+
setFeature(c, SM4, "hw.optional.arm.FEAT_SM4") // SM4 instructions
128+
setFeature(c, SVE, "hw.optional.arm.FEAT_SVE") // Scalable Vector Extension
127129
}

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