compiler: require ARMv8.1

Signed-off-by: Nuno Cruces <ncruces@users.noreply.github.com>

config_supported.go

@@ -9,6 +9,11 @@
 
 package wazero
 
+import "github.com/tetratelabs/wazero/internal/platform"
+
 func newRuntimeConfig() RuntimeConfig {
-	return NewRuntimeConfigCompiler()
+	if platform.CompilerSupported() {
+		return NewRuntimeConfigCompiler()
+	}
+	return NewRuntimeConfigInterpreter()
 }

internal/platform/cpuid.go

@@ -28,3 +28,8 @@ const (
 	CpuExtraFeatureAmd64ABM CpuFeature = 1 << 5
 	// Note: when adding new features, ensure that the feature is included in CpuFeatureFlags.Raw.
 )
+
+const (
+	// CpuFeatureArm64Atomic is the flag to query CpuFeatureFlags.Has for Large System Extensions capabilities on arm64
+	CpuFeatureArm64Atomic CpuFeature = 1 << 21
+)

internal/platform/cpuid_amd64.go

@@ -1,4 +1,4 @@
-//go:build amd64 && !tinygo
+//go:build gc
 
 package platform
 
@@ -12,7 +12,7 @@ type cpuFeatureFlags struct {
 }
 
 // cpuid exposes the CPUID instruction to the Go layer (https://www.amd.com/system/files/TechDocs/25481.pdf)
-// implemented in impl_amd64.s
+// implemented in cpuid_amd64.s
 func cpuid(arg1, arg2 uint32) (eax, ebx, ecx, edx uint32)
 
 // cpuidAsBitmap combines the result of invoking cpuid to uint64 bitmap.

internal/platform/cpuid_amd64.s

@@ -1,6 +1,9 @@
+//go:build gc
+
 #include "textflag.h"
 
 // lifted from github.com/intel-go/cpuid and src/internal/cpu/cpu_x86.s
+
 // func cpuid(arg1, arg2 uint32) (eax, ebx, ecx, edx uint32)
 TEXT ·cpuid(SB), NOSPLIT, $0-24
 	MOVL arg1+0(FP), AX
@@ -11,4 +14,3 @@ TEXT ·cpuid(SB), NOSPLIT, $0-24
 	MOVL CX, ecx+16(FP)
 	MOVL DX, edx+20(FP)
 	RET
-

internal/platform/cpuid_arm64.go

@@ -0,0 +1,76 @@
+//go:build gc
+
+package platform
+
+import "runtime"
+
+// CpuFeatures exposes the capabilities for this CPU, queried via the Has, HasExtra methods.
+var CpuFeatures = loadCpuFeatureFlags()
+
+// cpuFeatureFlags implements CpuFeatureFlags interface.
+type cpuFeatureFlags struct {
+	isar0 uint64
+	isar1 uint64
+}
+
+// implemented in cpuid_arm64.s
+func getisar0() uint64
+
+// implemented in cpuid_arm64.s
+func getisar1() uint64
+
+func loadCpuFeatureFlags() CpuFeatureFlags {
+	switch runtime.GOOS {
+	case "darwin", "windows":
+		// These OSes require ARMv8.1, which includes atomic instructions.
+		return &cpuFeatureFlags{
+			isar0: uint64(CpuFeatureArm64Atomic),
+			isar1: 0,
+		}
+	case "linux", "freebsd":
+		// These OSes allow reading the instruction set attribute registers.
+		return &cpuFeatureFlags{
+			isar0: getisar0(),
+			isar1: getisar1(),
+		}
+	default:
+		return &cpuFeatureFlags{}
+	}
+}
+
+// Has implements the same method on the CpuFeatureFlags interface.
+func (f *cpuFeatureFlags) Has(cpuFeature CpuFeature) bool {
+	return (f.isar0 & uint64(cpuFeature)) != 0
+}
+
+// HasExtra implements the same method on the CpuFeatureFlags interface.
+func (f *cpuFeatureFlags) HasExtra(cpuFeature CpuFeature) bool {
+	return (f.isar1 & uint64(cpuFeature)) != 0
+}
+
+// Raw implements the same method on the CpuFeatureFlags interface.
+func (f *cpuFeatureFlags) Raw() uint64 {
+	// Below, we only set the first 4 bits for the features we care about,
+	// instead of setting all the unnecessary bits obtained from the CPUID instruction.
+	var ret uint64
+	switch runtime.GOARCH {
+	case "arm64":
+		if f.Has(CpuFeatureArm64Atomic) {
+			ret = 1 << 0
+		}
+	case "amd64":
+		if f.Has(CpuFeatureAmd64SSE3) {
+			ret = 1 << 0
+		}
+		if f.Has(CpuFeatureAmd64SSE4_1) {
+			ret |= 1 << 1
+		}
+		if f.Has(CpuFeatureAmd64SSE4_2) {
+			ret |= 1 << 2
+		}
+		if f.HasExtra(CpuExtraFeatureAmd64ABM) {
+			ret |= 1 << 3
+		}
+	}
+	return ret
+}

internal/platform/cpuid_arm64.s

@@ -0,0 +1,21 @@
+//go:build gc
+
+#include "textflag.h"
+
+// lifted from github.com/golang/sys and cpu/cpu_arm64.s
+
+// func getisar0() uint64
+TEXT ·getisar0(SB), NOSPLIT, $0-8
+	// get Instruction Set Attributes 0 into x0
+	// mrs x0, ID_AA64ISAR0_EL1 = d5380600
+	WORD $0xd5380600
+	MOVD R0, ret+0(FP)
+	RET
+
+// func getisar1() uint64
+TEXT ·getisar1(SB), NOSPLIT, $0-8
+	// get Instruction Set Attributes 1 into x0
+	// mrs x0, ID_AA64ISAR1_EL1 = d5380620
+	WORD $0xd5380620
+	MOVD R0, ret+0(FP)
+	RET

internal/platform/cpuid_unsupported.go

@@ -1,4 +1,4 @@
-//go:build !amd64 || tinygo
+//go:build !(amd64 || arm64) || !gc
 
 package platform
 

internal/platform/platform.go

@@ -11,7 +11,7 @@ import (
 // archRequirementsVerified is set by platform-specific init to true if the platform is supported
 var archRequirementsVerified bool
 
-// CompilerSupported is exported for tests and includes constraints here and also the assembler.
+// CompilerSupported includes constraints here and also the assembler.
 func CompilerSupported() bool {
 	switch runtime.GOOS {
 	case "linux", "darwin", "freebsd", "netbsd", "dragonfly", "windows":

internal/platform/platform_arm64.go

@@ -2,6 +2,6 @@ package platform
 
 // init verifies that the current CPU supports the required ARM64 features
 func init() {
-	// No further checks currently needed.
-	archRequirementsVerified = true
+	// Ensure atomic instructions are supported.
+	archRequirementsVerified = CpuFeatures.Has(CpuFeatureArm64Atomic)
 }