cmd/compile: don't copy all type nodes for builtin functions

Only copy the ones that actually change.  Also combine deep and substAny
functions into one.  The Type.Copyany field is now unused, so remove it.

Passes toolstash -cmp.

Change-Id: Id28a9bf144ecf3e522aad00496f8a21ae2b74680
Reviewed-on: https://go-review.googlesource.com/20600
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>

src/cmd/compile/internal/gc/subr.go

@@ -1078,51 +1078,91 @@ func substArgTypes(np **Node, types ...*Type) {
 	for _, t := range types {
 		dowidth(t)
 	}
-	n.Type = deep(n.Type)
-	substAny(&n.Type, &types)
+	n.Type = substAny(n.Type, &types)
 	if len(types) > 0 {
 		Fatalf("substArgTypes: too many argument types")
 	}
 }
 
-// substAny walks *tp, replacing instances of "any" with successive
-// elements removed from types.
-func substAny(tp **Type, types *[]*Type) {
-	for {
-		t := *tp
-		if t == nil {
-			return
-		}
-		if t.Etype == TANY && t.Copyany {
-			if len(*types) == 0 {
-				Fatalf("substArgTypes: not enough argument types")
-			}
-			*tp = (*types)[0]
-			*types = (*types)[1:]
-		}
-
-		switch t.Etype {
-		case TPTR32, TPTR64, TCHAN, TARRAY:
-			tp = &t.Type
-			continue
-
-		case TMAP:
-			substAny(&t.Down, types)
-			tp = &t.Type
-			continue
-
-		case TFUNC:
-			substAny(t.RecvsP(), types)
-			substAny(t.ParamsP(), types)
-			substAny(t.ResultsP(), types)
-
-		case TSTRUCT:
-			for t, it := IterFields(t); t != nil; t = it.Next() {
-				substAny(&t.Type, types)
-			}
-		}
-		return
+// substAny walks t, replacing instances of "any" with successive
+// elements removed from types.  It returns the substituted type.
+func substAny(t *Type, types *[]*Type) *Type {
+	if t == nil {
+		return nil
 	}
+
+	switch t.Etype {
+	default:
+		// Leave the type unchanged.
+
+	case TANY:
+		if len(*types) == 0 {
+			Fatalf("substArgTypes: not enough argument types")
+		}
+		t = (*types)[0]
+		*types = (*types)[1:]
+
+	case TPTR32, TPTR64, TCHAN, TARRAY, TFIELD:
+		elem := substAny(t.Type, types)
+		if elem != t.Type {
+			t = t.Copy()
+			t.Type = elem
+		}
+
+	case TMAP:
+		key := substAny(t.Down, types)
+		val := substAny(t.Type, types)
+		if key != t.Down || val != t.Type {
+			t = t.Copy()
+			t.Down = key
+			t.Type = val
+		}
+
+	case TFUNC:
+		recvs := substAny(t.Recvs(), types)
+		params := substAny(t.Params(), types)
+		results := substAny(t.Results(), types)
+		if recvs != t.Recvs() || params != t.Params() || results != t.Results() {
+			// Note that this code has to be aware of the
+			// representation underlying Recvs/Results/Params.
+			if recvs == t.Recvs() {
+				recvs = recvs.Copy()
+			}
+			if results == t.Results() {
+				results = results.Copy()
+			}
+			t = t.Copy()
+			*t.RecvsP() = recvs
+			*t.ResultsP() = results
+			*t.ParamsP() = params
+		}
+
+	case TSTRUCT:
+		// nfs only has to be big enough for the builtin functions.
+		var nfs [8]*Type
+		fields := t.FieldSlice()
+		changed := false
+		for i, f := range fields {
+			nf := substAny(f, types)
+			if nf != f {
+				if !changed {
+					for j := 0; j < i; j++ {
+						nfs[j] = fields[j].Copy()
+					}
+				}
+				changed = true
+			} else if changed {
+				nf = f.Copy()
+			}
+			nfs[i] = nf
+		}
+		if changed {
+			t = t.Copy()
+			t.SetFields(nfs[:len(fields)])
+		}
+	}
+
+	return t
 }
 
 // Is this a 64-bit type?
@@ -1166,50 +1206,6 @@ func Noconv(t1 *Type, t2 *Type) bool {
 	return false
 }
 
-func deep(t *Type) *Type {
-	if t == nil {
-		return nil
-	}
-
-	var nt *Type
-	switch t.Etype {
-	default:
-		nt = t // share from here down
-
-	case TANY:
-		nt = t.Copy()
-		nt.Copyany = true
-
-	case TPTR32, TPTR64, TCHAN, TARRAY:
-		nt = t.Copy()
-		nt.Type = deep(t.Type)
-
-	case TMAP:
-		nt = t.Copy()
-		nt.Down = deep(t.Down)
-		nt.Type = deep(t.Type)
-
-	case TFUNC:
-		nt = t.Copy()
-		*nt.RecvsP() = deep(t.Recvs())
-		*nt.ResultsP() = deep(t.Results())
-		*nt.ParamsP() = deep(t.Params())
-
-	case TSTRUCT:
-		nt = t.Copy()
-		nt.Type = t.Type.Copy()
-		xt := nt.Type
-
-		for t, it := IterFields(t); t != nil; t = it.Next() {
-			xt.Type = deep(t.Type)
-			xt.Down = t.Down.Copy()
-			xt = xt.Down
-		}
-	}
-
-	return nt
-}
-
 func syslook(name string) *Node {
 	s := Pkglookup(name, Runtimepkg)
 	if s == nil || s.Def == nil {

src/cmd/compile/internal/gc/type.go

@@ -110,8 +110,7 @@ type Type struct {
 	Printed     bool
 	Embedded    uint8 // TFIELD embedded type
 	Funarg      bool  // on TSTRUCT and TFIELD
-	Copyany     bool
-	Local       bool // created in this file
+	Local       bool  // created in this file
 	Deferwidth  bool
 	Broke       bool // broken type definition.
 	Isddd       bool // TFIELD is ... argument