cmd/compile/internal/ssa: remove redundant "type:" prefix check

Remove redundant "type:" prefix check on symbol names in isFixedLoad,
also refactor some duplicate code into methods.

Change-Id: I8358422596eea8c39d1a30a554bd0aae8b570038
Reviewed-on: https://go-review.googlesource.com/c/go/+/701275
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
Auto-Submit: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>

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

@@ -2059,12 +2059,12 @@ func isFixedLoad(v *Value, sym Sym, off int64) bool {
 		return false
 	}
 
-	if strings.HasPrefix(lsym.Name, "type:") {
+	if ti := lsym.TypeInfo(); ti != nil {
 		// Type symbols do not contain information about their fields, unlike the cases above.
 		// Hand-implement field accesses.
 		// TODO: can this be replaced with reflectdata.writeType and just use the code above?
 
-		t := (*lsym.Extra).(*obj.TypeInfo).Type.(*types.Type)
+		t := ti.Type.(*types.Type)
 
 		for _, f := range rttype.Type.Fields() {
 			if f.Offset == off && copyCompatibleType(v.Type, f.Type) {
@@ -2118,12 +2118,12 @@ func rewriteFixedLoad(v *Value, sym Sym, sb *Value, off int64) *Value {
 		base.Fatalf("fixedLoad data not known for %s:%d", sym, off)
 	}
 
-	if strings.HasPrefix(lsym.Name, "type:") {
+	if ti := lsym.TypeInfo(); ti != nil {
 		// Type symbols do not contain information about their fields, unlike the cases above.
 		// Hand-implement field accesses.
 		// TODO: can this be replaced with reflectdata.writeType and just use the code above?
 
-		t := (*lsym.Extra).(*obj.TypeInfo).Type.(*types.Type)
+		t := ti.Type.(*types.Type)
 
 		ptrSizedOpConst := OpConst64
 		if f.Config.PtrSize == 4 {
@@ -2613,10 +2613,7 @@ func isDirectType1(v *Value) bool {
 		return isDirectType2(v.Args[0])
 	case OpAddr:
 		lsym := v.Aux.(*obj.LSym)
-		if lsym.Extra == nil {
+		if ti := lsym.TypeInfo(); ti != nil {
-			return false
-		}
-		if ti, ok := (*lsym.Extra).(*obj.TypeInfo); ok {
 			return types.IsDirectIface(ti.Type.(*types.Type))
 		}
 	}
@@ -2649,10 +2646,7 @@ func isDirectIface1(v *Value, depth int) bool {
 		return isDirectIface2(v.Args[0], depth-1)
 	case OpAddr:
 		lsym := v.Aux.(*obj.LSym)
-		if lsym.Extra == nil {
+		if ii := lsym.ItabInfo(); ii != nil {
-			return false
-		}
-		if ii, ok := (*lsym.Extra).(*obj.ItabInfo); ok {
 			return types.IsDirectIface(ii.Type.(*types.Type))
 		}
 	case OpConstNil:

src/cmd/internal/obj/link.go

@@ -464,7 +464,7 @@ type LSym struct {
 	P      []byte
 	R      []Reloc
 
-	Extra *interface{} // *FuncInfo, *VarInfo, *FileInfo, or *TypeInfo, if present
+	Extra *interface{} // *FuncInfo, *VarInfo, *FileInfo, *TypeInfo, or *ItabInfo, if present
 
 	Pkg    string
 	PkgIdx int32
@@ -604,6 +604,15 @@ func (s *LSym) NewTypeInfo() *TypeInfo {
 	return t
 }
 
+// TypeInfo returns the *TypeInfo associated with s, or else nil.
+func (s *LSym) TypeInfo() *TypeInfo {
+	if s.Extra == nil {
+		return nil
+	}
+	t, _ := (*s.Extra).(*TypeInfo)
+	return t
+}
+
 // An ItabInfo contains information for a symbol
 // that contains a runtime.itab.
 type ItabInfo struct {
@@ -620,6 +629,15 @@ func (s *LSym) NewItabInfo() *ItabInfo {
 	return t
 }
 
+// ItabInfo returns the *ItabInfo associated with s, or else nil.
+func (s *LSym) ItabInfo() *ItabInfo {
+	if s.Extra == nil {
+		return nil
+	}
+	i, _ := (*s.Extra).(*ItabInfo)
+	return i
+}
+
 // WasmImport represents a WebAssembly (WASM) imported function with
 // parameters and results translated into WASM types based on the Go function
 // declaration.