cpu: support darwin/arm64 CPU feature detection

cpu/cpu_arm64.go

@@ -44,7 +44,7 @@ func archInit() {
 	switch runtime.GOOS {
 	case "freebsd":
 		readARM64Registers()
-	case "linux", "netbsd", "openbsd":
+	case "linux", "netbsd", "openbsd", "darwin":
 		doinit()
 	default:
 		// Many platforms don't seem to allow reading these registers.

cpu/cpu_darwin_arm64.go

@@ -0,0 +1,55 @@
+// Copyright 2021 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.
+
+//go:build darwin && arm64 && !ios
+// +build darwin,arm64,!ios
+
+package cpu
+
+const (
+	commpageHasNeonFP16      = 0x00000008         // ARM v8.2 NEON FP16 supported
+	commpageHasNeon          = 0x00000100         // Advanced SIMD is supported
+	commpageHasNeonHPFP      = 0x00000200         // Advanced SIMD half-precision
+	commpageHasVfp           = 0x00000400         // VFP is supported
+	commpageHasEvent         = 0x00001000         // WFE/SVE and period event wakeup
+	commpageHasARMv82FHM     = 0x00004000         // Optional ARMv8.2 FMLAL/FMLSL instructions (required in ARMv8.4)
+	commpageHasARMv8Crypto   = 0x01000000         // Optional ARMv8 Crypto extensions
+	commpageHasARMv81Atomics = 0x02000000         // ARMv8.1 Atomic instructions supported
+	commpageHasARMv8Crc32    = 0x04000000         // Optional ARMv8 crc32 instructions (required in ARMv8.1)
+	commpageHasARMv82SHA512  = 0x80000000         // Optional ARMv8.2 SHA512 instructions
+	commpageHasARMv82SHA3    = 0x0000000100000000 // Optional ARMv8.2 SHA3 instructions
+)
+
+func doinit() {
+	ARM64.HasFP = darwinCheckFeatureEnabled(commpageHasVfp)
+	ARM64.HasASIMD = darwinCheckFeatureEnabled(commpageHasNeon)
+	ARM64.HasCRC32 = darwinCheckFeatureEnabled(commpageHasARMv8Crc32)
+	ARM64.HasATOMICS = darwinCheckFeatureEnabled(commpageHasARMv81Atomics)
+	ARM64.HasFPHP = darwinCheckFeatureEnabled(commpageHasNeonFP16)
+	ARM64.HasASIMDHP = darwinCheckFeatureEnabled(commpageHasNeonHPFP)
+	ARM64.HasSHA3 = darwinCheckFeatureEnabled(commpageHasARMv82SHA3)
+	ARM64.HasSHA512 = darwinCheckFeatureEnabled(commpageHasARMv82SHA512)
+	ARM64.HasASIMDFHM = darwinCheckFeatureEnabled(commpageHasARMv82FHM)
+	ARM64.HasSVE = darwinCheckFeatureEnabled(commpageHasEvent)
+
+	// There are no hw.optional sysctl values for the below features on Mac OS 11.0
+	// to detect their supported state dynamically. Assume the CPU features that
+	// Apple Silicon M1 supports to be available as a minimal set of features
+	// to all Go programs running on darwin/arm64.
+	ARM64.HasEVTSTRM = true
+	ARM64.HasAES = true
+	ARM64.HasPMULL = true
+	ARM64.HasSHA1 = true
+	ARM64.HasSHA2 = true
+	ARM64.HasCPUID = true
+	ARM64.HasASIMDRDM = true
+	ARM64.HasJSCVT = true
+	ARM64.HasLRCPC = true
+	ARM64.HasDCPOP = true
+	ARM64.HasSM3 = true
+	ARM64.HasSM4 = true
+	ARM64.HasASIMDDP = true
+}
+
+func darwinCheckFeatureEnabled(feature_vec uint64) bool

cpu/cpu_darwin_arm64.s

@@ -0,0 +1,29 @@
+//go:build arm64 && gc
+// +build arm64
+// +build gc
+
+#include "textflag.h"
+
+// func darwinCheckFeatureEnabled(feature_vec uint64) bool
+TEXT ·darwinCheckFeatureEnabled(SB), NOSPLIT, $0-8
+    MOVD    feature_vec+0(FP), R0
+    MOVD    $0, ret+0(FP) // default to false
+    MOVD    $1, R2        // set R2 as true boolean constan
+
+#ifdef GOOS_darwin   // return if not darwin
+#ifdef GOARCH_arm64  // return if not arm64
+// These values from:
+// https://github.com/apple/darwin-xnu/blob/main/osfmk/arm/cpu_capabilities.h
+#define arm_commpage64_base_address         0x0000000fffffc000
+#define arm_commpage64_cpu_capabilities64   (arm_commpage64_base_address+0x010)
+    MOVD    $0xffffc000, R1
+    MOVK    $(0xf<<32), R1
+    MOVD    (R1), R1
+    AND   R1, R0
+    CBZ      R0, no_feature
+    MOVD    R2, ret+8(FP)
+
+no_feature:
+#endif
+#endif
+    RET

cpu/cpu_other_arm64.go

@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build !linux && !netbsd && !openbsd && arm64
-// +build !linux,!netbsd,!openbsd,arm64
+//go:build !linux && !netbsd && !openbsd && arm64 && !darwin
+// +build !linux,!netbsd,!openbsd,arm64,!darwin
 
 package cpu