internal/abi: use arch family instead of arch string

No point in using string comparison when we can use integer comparison instead.

Unify the constants in cmd/internal/sys and internal/goarch while
we are at it.

Change-Id: I5681a601030307b7b286f958a8965559cb43506d
Reviewed-on: https://go-review.googlesource.com/c/go/+/652175
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Stapelberg <stapelberg@google.com>
Reviewed-by: Keith Randall <khr@google.com>

src/cmd/compile/internal/ssagen/ssa.go

@@ -2033,7 +2033,7 @@ func (s *state) stmt(n ir.Node) {
 
 		// Check the cache first.
 		var merge *ssa.Block
-		if base.Flag.N == 0 && rtabi.UseInterfaceSwitchCache(Arch.LinkArch.Name) {
+		if base.Flag.N == 0 && rtabi.UseInterfaceSwitchCache(Arch.LinkArch.Family) {
 			// Note: we can only use the cache if we have the right atomic load instruction.
 			// Double-check that here.
 			if intrinsics.lookup(Arch.LinkArch.Arch, "internal/runtime/atomic", "Loadp") == nil {
@@ -5768,7 +5768,7 @@ func (s *state) dottype1(pos src.XPos, src, dst *types.Type, iface, source, targ
 		var d *ssa.Value
 		if descriptor != nil {
 			d = s.newValue1A(ssa.OpAddr, byteptr, descriptor, s.sb)
-			if base.Flag.N == 0 && rtabi.UseInterfaceSwitchCache(Arch.LinkArch.Name) {
+			if base.Flag.N == 0 && rtabi.UseInterfaceSwitchCache(Arch.LinkArch.Family) {
 				// Note: we can only use the cache if we have the right atomic load instruction.
 				// Double-check that here.
 				if intrinsics.lookup(Arch.LinkArch.Arch, "internal/runtime/atomic", "Loadp") == nil {

src/cmd/internal/sys/arch.go

@@ -4,25 +4,26 @@
 
 package sys
 
-import "encoding/binary"
+import (
+	"encoding/binary"
+	"internal/goarch"
+)
 
-// ArchFamily represents a family of one or more related architectures.
+// TODO: just use goarch.ArchFamilyType directly
-// For example, ppc64 and ppc64le are both members of the PPC64 family.
+type ArchFamily = goarch.ArchFamilyType
-type ArchFamily byte
 
 const (
-	NoArch ArchFamily = iota
+	AMD64   = goarch.AMD64
-	AMD64
+	ARM     = goarch.ARM
-	ARM
+	ARM64   = goarch.ARM64
-	ARM64
+	I386    = goarch.I386
-	I386
+	Loong64 = goarch.LOONG64
-	Loong64
+	MIPS    = goarch.MIPS
-	MIPS
+	MIPS64  = goarch.MIPS64
-	MIPS64
+	PPC64   = goarch.PPC64
-	PPC64
+	RISCV64 = goarch.RISCV64
-	RISCV64
+	S390X   = goarch.S390X
-	S390X
+	Wasm    = goarch.WASM
-	Wasm
 )
 
 // Arch represents an individual architecture.

src/internal/abi/switch.go

@@ -4,6 +4,8 @@
 
 package abi
 
+import "internal/goarch"
+
 type InterfaceSwitch struct {
 	Cache  *InterfaceSwitchCache
 	NCases int
@@ -27,11 +29,11 @@ type InterfaceSwitchCacheEntry struct {
 	Itab uintptr
 }
 
-func UseInterfaceSwitchCache(goarch string) bool {
+func UseInterfaceSwitchCache(arch goarch.ArchFamilyType) bool {
 	// We need an atomic load instruction to make the cache multithreaded-safe.
 	// (AtomicLoadPtr needs to be implemented in cmd/compile/internal/ssa/_gen/ARCH.rules.)
-	switch goarch {
+	switch arch {
-	case "amd64", "arm64", "loong64", "mips", "mipsle", "mips64", "mips64le", "ppc64", "ppc64le", "riscv64", "s390x":
+	case goarch.AMD64, goarch.ARM64, goarch.LOONG64, goarch.MIPS, goarch.MIPS64, goarch.PPC64, goarch.RISCV64, goarch.S390X:
 		return true
 	default:
 		return false

src/internal/goarch/goarch.go

@@ -12,6 +12,8 @@ package goarch
 //
 //go:generate go run gengoarch.go
 
+// ArchFamilyType represents a family of one or more related architectures.
+// For example, ppc64 and ppc64le are both members of the PPC64 family.
 type ArchFamilyType int
 
 const (

src/runtime/iface.go

@@ -474,7 +474,7 @@ func typeAssert(s *abi.TypeAssert, t *_type) *itab {
 		tab = getitab(s.Inter, t, s.CanFail)
 	}
 
-	if !abi.UseInterfaceSwitchCache(GOARCH) {
+	if !abi.UseInterfaceSwitchCache(goarch.ArchFamily) {
 		return tab
 	}
 
@@ -574,7 +574,7 @@ func interfaceSwitch(s *abi.InterfaceSwitch, t *_type) (int, *itab) {
 		}
 	}
 
-	if !abi.UseInterfaceSwitchCache(GOARCH) {
+	if !abi.UseInterfaceSwitchCache(goarch.ArchFamily) {
 		return case_, tab
 	}