cpu: use IsProcessorFeaturePresent to calculate ARM64 on windows

This CL started as revert of CL 757482.

Fixes golang/go#76791

Change-Id: Iaa78c73a6dde8d735e74e2c57c86375ccd5902c7
Reviewed-on: https://go-review.googlesource.com/c/sys/+/758960
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Quim Muntal <quimmuntal@gmail.com>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

cpu/cpu_other_arm64.go

diff --git a/cpu/cpu_other_arm64.go b/cpu/cpu_other_arm64.go
index 53f814d..6c7c5bf 100644
--- a/cpu/cpu_other_arm64.go
+++ b/cpu/cpu_other_arm64.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build !darwin && !linux && !netbsd && !openbsd && arm64
+//go:build !darwin && !linux && !netbsd && !openbsd && !windows && arm64
 
 package cpu
 

cpu/cpu_windows.go

diff --git a/cpu/cpu_windows.go b/cpu/cpu_windows.go
new file mode 100644
index 0000000..99ec8fd
--- /dev/null
+++ b/cpu/cpu_windows.go
@@ -0,0 +1,26 @@
+// Copyright 2026 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
+
+//go:generate go run golang.org/x/sys/windows/mkwinsyscall -systemdll=false -output zcpu_windows.go cpu_windows.go
+
+//sys	isProcessorFeaturePresent(ProcessorFeature uint32) (ret bool) = kernel32.IsProcessorFeaturePresent
+
+// The processor features to be tested for IsProcessorFeaturePresent, see
+// https://learn.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-isprocessorfeaturepresent
+const (
+	_PF_ARM_V8_CRYPTO_INSTRUCTIONS_AVAILABLE  = 30
+	_PF_ARM_V8_CRC32_INSTRUCTIONS_AVAILABLE   = 31
+	_PF_ARM_V81_ATOMIC_INSTRUCTIONS_AVAILABLE = 34
+	_PF_ARM_V82_DP_INSTRUCTIONS_AVAILABLE     = 43
+
+	_PF_ARM_V83_JSCVT_INSTRUCTIONS_AVAILABLE = 44
+	_PF_ARM_V83_LRCPC_INSTRUCTIONS_AVAILABLE = 45
+	_PF_ARM_SVE_INSTRUCTIONS_AVAILABLE       = 46
+	_PF_ARM_SVE2_INSTRUCTIONS_AVAILABLE      = 47
+
+	_PF_ARM_SHA3_INSTRUCTIONS_AVAILABLE   = 64
+	_PF_ARM_SHA512_INSTRUCTIONS_AVAILABLE = 65
+)

cpu/cpu_windows_arm64.go

diff --git a/cpu/cpu_windows_arm64.go b/cpu/cpu_windows_arm64.go
new file mode 100644
index 0000000..034732e
--- /dev/null
+++ b/cpu/cpu_windows_arm64.go
@@ -0,0 +1,38 @@
+// Copyright 2026 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
+
+func doinit() {
+	// set HasASIMD and HasFP to true as per
+	// https://learn.microsoft.com/en-us/cpp/build/arm64-windows-abi-conventions?view=msvc-170#base-requirements
+	//
+	// The ARM64 version of Windows always presupposes that it's running on an ARMv8 or later architecture.
+	// Both floating-point and NEON support are presumed to be present in hardware.
+	//
+	ARM64.HasASIMD = true
+	ARM64.HasFP = true
+
+	if isProcessorFeaturePresent(_PF_ARM_V8_CRYPTO_INSTRUCTIONS_AVAILABLE) {
+		ARM64.HasAES = true
+		ARM64.HasPMULL = true
+		ARM64.HasSHA1 = true
+		ARM64.HasSHA2 = true
+	}
+	ARM64.HasSHA3 = isProcessorFeaturePresent(_PF_ARM_SHA3_INSTRUCTIONS_AVAILABLE)
+	ARM64.HasCRC32 = isProcessorFeaturePresent(_PF_ARM_V8_CRC32_INSTRUCTIONS_AVAILABLE)
+	ARM64.HasSHA512 = isProcessorFeaturePresent(_PF_ARM_SHA512_INSTRUCTIONS_AVAILABLE)
+	ARM64.HasATOMICS = isProcessorFeaturePresent(_PF_ARM_V81_ATOMIC_INSTRUCTIONS_AVAILABLE)
+	if isProcessorFeaturePresent(_PF_ARM_V82_DP_INSTRUCTIONS_AVAILABLE) {
+		ARM64.HasASIMDDP = true
+		ARM64.HasASIMDRDM = true
+	}
+	if isProcessorFeaturePresent(_PF_ARM_V83_LRCPC_INSTRUCTIONS_AVAILABLE) {
+		ARM64.HasLRCPC = true
+		ARM64.HasSM3 = true
+	}
+	ARM64.HasSVE = isProcessorFeaturePresent(_PF_ARM_SVE_INSTRUCTIONS_AVAILABLE)
+	ARM64.HasSVE2 = isProcessorFeaturePresent(_PF_ARM_SVE2_INSTRUCTIONS_AVAILABLE)
+	ARM64.HasJSCVT = isProcessorFeaturePresent(_PF_ARM_V83_JSCVT_INSTRUCTIONS_AVAILABLE)
+}

cpu/zcpu_windows.go

diff --git a/cpu/zcpu_windows.go b/cpu/zcpu_windows.go
new file mode 100644
index 0000000..6411a7a
--- /dev/null
+++ b/cpu/zcpu_windows.go
@@ -0,0 +1,48 @@
+// Code generated by 'go generate'; DO NOT EDIT.
+
+package cpu
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+var _ unsafe.Pointer
+
+// Do the interface allocations only once for common
+// Errno values.
+const (
+	errnoERROR_IO_PENDING = 997
+)
+
+var (
+	errERROR_IO_PENDING error = syscall.Errno(errnoERROR_IO_PENDING)
+	errERROR_EINVAL     error = syscall.EINVAL
+)
+
+// errnoErr returns common boxed Errno values, to prevent
+// allocations at runtime.
+func errnoErr(e syscall.Errno) error {
+	switch e {
+	case 0:
+		return errERROR_EINVAL
+	case errnoERROR_IO_PENDING:
+		return errERROR_IO_PENDING
+	}
+	// TODO: add more here, after collecting data on the common
+	// error values see on Windows. (perhaps when running
+	// all.bat?)
+	return e
+}
+
+var (
+	modkernel32 = syscall.NewLazyDLL("kernel32.dll")
+
+	procIsProcessorFeaturePresent = modkernel32.NewProc("IsProcessorFeaturePresent")
+)
+
+func isProcessorFeaturePresent(ProcessorFeature uint32) (ret bool) {
+	r0, _, _ := syscall.SyscallN(procIsProcessorFeaturePresent.Addr(), uintptr(ProcessorFeature))
+	ret = r0 != 0
+	return
+}