cmd/compile/internal/ir: remove AsNode

Except for a single call site in escape analysis, every use of
ir.AsNode involves a types.Object that's known to contain
an *ir.Name. Asserting directly to that type makes the code simpler
and more efficient.

The one use in escape analysis is extended to handle nil correctly
without it.

Change-Id: I694ae516903e541341d82c2f65a9155e4b0a9809
Reviewed-on: https://go-review.googlesource.com/c/go/+/520775
TryBot-Bypass: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Auto-Submit: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>

src/cmd/compile/internal/escape/call.go

@@ -321,7 +321,10 @@ func (e *escape) tagHole(ks []hole, fn *ir.Name, param *types.Field) hole {
 	}
 
 	if e.inMutualBatch(fn) {
-		return e.addr(ir.AsNode(param.Nname))
+		if param.Nname == nil {
+			return e.discardHole()
+		}
+		return e.addr(param.Nname.(*ir.Name))
 	}
 
 	// Call to previously tagged function.

src/cmd/compile/internal/ir/expr.go

@@ -1110,7 +1110,7 @@ func IsReflectHeaderDataField(l Node) bool {
 func ParamNames(ft *types.Type) []Node {
 	args := make([]Node, ft.NumParams())
 	for i, f := range ft.Params().FieldSlice() {
-		args[i] = AsNode(f.Nname)
+		args[i] = f.Nname.(*Name)
 	}
 	return args
 }

src/cmd/compile/internal/ir/node.go

@@ -462,13 +462,6 @@ const (
 
 )
 
-func AsNode(n types.Object) Node {
-	if n == nil {
-		return nil
-	}
-	return n.(Node)
-}
-
 var BlankNode *Name
 
 func IsConst(n Node, ct constant.Kind) bool {

src/cmd/compile/internal/reflectdata/alg.go

@@ -153,8 +153,8 @@ func hashFunc(t *types.Type) *ir.Func {
 	sym.Def = fn.Nname
 	fn.Pragma |= ir.Noinline // TODO(mdempsky): We need to emit this during the unified frontend instead, to allow inlining.
 
-	np := ir.AsNode(fn.Type().Params().Field(0).Nname)
+	np := fn.Type().Params().Field(0).Nname.(*ir.Name)
-	nh := ir.AsNode(fn.Type().Params().Field(1).Nname)
+	nh := fn.Type().Params().Field(1).Nname.(*ir.Name)
 
 	switch t.Kind() {
 	case types.TARRAY:
@@ -375,9 +375,9 @@ func eqFunc(t *types.Type) *ir.Func {
 	sym.Def = fn.Nname
 	fn.Pragma |= ir.Noinline // TODO(mdempsky): We need to emit this during the unified frontend instead, to allow inlining.
 
-	np := ir.AsNode(fn.Type().Params().Field(0).Nname)
+	np := fn.Type().Params().Field(0).Nname.(*ir.Name)
-	nq := ir.AsNode(fn.Type().Params().Field(1).Nname)
+	nq := fn.Type().Params().Field(1).Nname.(*ir.Name)
-	nr := ir.AsNode(fn.Type().Results().Field(0).Nname)
+	nr := fn.Type().Results().Field(0).Nname.(*ir.Name)
 
 	// Label to jump to if an equality test fails.
 	neq := typecheck.AutoLabel(".neq")

src/cmd/compile/internal/test/abiutilsaux_test.go

@@ -76,7 +76,7 @@ func tokenize(src string) []string {
 }
 
 func verifyParamResultOffset(t *testing.T, f *types.Field, r abi.ABIParamAssignment, which string, idx int) int {
-	n := ir.AsNode(f.Nname).(*ir.Name)
+	n := f.Nname.(*ir.Name)
 	if n.FrameOffset() != int64(r.Offset()) {
 		t.Errorf("%s %d: got offset %d wanted %d t=%v",
 			which, idx, r.Offset(), n.Offset_, f.Type)

src/cmd/compile/internal/typecheck/syms.go

@@ -16,7 +16,7 @@ func LookupRuntime(name string) *ir.Name {
 	if s == nil || s.Def == nil {
 		base.Fatalf("LookupRuntime: can't find runtime.%s", name)
 	}
-	return ir.AsNode(s.Def).(*ir.Name)
+	return s.Def.(*ir.Name)
 }
 
 // SubstArgTypes substitutes the given list of types for
@@ -126,5 +126,5 @@ func LookupCoverage(name string) *ir.Name {
 	if sym == nil {
 		base.Fatalf("LookupCoverage: can't find runtime/coverage.%s", name)
 	}
-	return ir.AsNode(sym.Def).(*ir.Name)
+	return sym.Def.(*ir.Name)
 }