cmd/compile: more use of IterXXX functions

This CL was mostly produced by a one-off automated rewrite tool
looking for statements like "for X := T.Type; X != nil; X = X.Down"
and a few minor variations.

Passes toolstash -cmp.

Change-Id: Ib22705e37d078ef97841ee2e08f60bdbcabb94ad
Reviewed-on: https://go-review.googlesource.com/20520
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

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

@@ -135,7 +135,7 @@ func algtype1(t *Type, bad **Type) int {
 		}
 
 		ret := AMEM
-		for f := t.Type; f != nil; f = f.Down {
+		for f, it := IterFields(t); f != nil; f = it.Next() {
 			// All fields must be comparable.
 			a := algtype1(f.Type, bad)
 			if a == ANOEQ {

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

@@ -19,7 +19,7 @@ func Rnd(o int64, r int64) int64 {
 
 func offmod(t *Type) {
 	o := int32(0)
-	for f := t.Type; f != nil; f = f.Down {
+	for f, it := IterFields(t); f != nil; f = it.Next() {
 		if f.Etype != TFIELD {
 			Fatalf("offmod: not TFIELD: %v", Tconv(f, obj.FmtLong))
 		}
@@ -40,7 +40,7 @@ func widstruct(errtype *Type, t *Type, o int64, flag int) int64 {
 	}
 	lastzero := int64(0)
 	var w int64
-	for f := t.Type; f != nil; f = f.Down {
+	for f, it := IterFields(t); f != nil; f = it.Next() {
 		if f.Etype != TFIELD {
 			Fatalf("widstruct: not TFIELD: %v", Tconv(f, obj.FmtLong))
 		}

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

@@ -465,7 +465,7 @@ func (p *exporter) typ(t *Type) {
 		// TODO(gri) Determine if they are already sorted
 		// in which case we can drop this step.
 		var methods []*Type
-		for m := t.Method; m != nil; m = m.Down {
+		for m, it := IterMethods(t); m != nil; m = it.Next() {
 			methods = append(methods, m)
 		}
 		sort.Sort(methodbyname(methods))
@@ -559,7 +559,7 @@ func (p *exporter) fieldList(t *Type) {
 	}
 
 	p.int(countfield(t))
-	for f := t.Type; f != nil; f = f.Down {
+	for f, it := IterFields(t); f != nil; f = it.Next() {
 		p.field(f)
 		if p.trace && f.Down != nil {
 			p.tracef("\n")
@@ -592,7 +592,7 @@ func (p *exporter) methodList(t *Type) {
 	}
 
 	p.int(countfield(t))
-	for m := t.Type; m != nil; m = m.Down {
+	for m, it := IterFields(t); m != nil; m = it.Next() {
 		p.method(m)
 		if p.trace && m.Down != nil {
 			p.tracef("\n")
@@ -657,7 +657,7 @@ func (p *exporter) paramList(params *Type) {
 		n = -n
 	}
 	p.int(n)
-	for q := params.Type; q != nil; q = q.Down {
+	for q, it := IterFields(params); q != nil; q = it.Next() {
 		p.param(q, n)
 	}
 }

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

@@ -834,7 +834,7 @@ func tostruct0(t *Type, l []*Node) {
 		tp = &f.Down
 	}
 
-	for f := t.Type; f != nil && !t.Broke; f = f.Down {
+	for f, it := IterFields(t); f != nil && !t.Broke; f = it.Next() {
 		if f.Broke {
 			t.Broke = true
 		}
@@ -868,7 +868,7 @@ func tofunargs(l []*Node) *Type {
 		tp = &f.Down
 	}
 
-	for f := t.Type; f != nil && !t.Broke; f = f.Down {
+	for f, it := IterFields(t); f != nil && !t.Broke; f = it.Next() {
 		if f.Broke {
 			t.Broke = true
 		}
@@ -961,7 +961,7 @@ func tointerface0(t *Type, l []*Node) *Type {
 
 		if n.Left == nil && f.Type.Etype == TINTER {
 			// embedded interface, inline methods
-			for t1 := f.Type.Type; t1 != nil; t1 = t1.Down {
+			for t1, it := IterFields(f.Type); t1 != nil; t1 = it.Next() {
 				f = typ(TFIELD)
 				f.Type = t1.Type
 				f.Broke = t1.Broke
@@ -978,7 +978,7 @@ func tointerface0(t *Type, l []*Node) *Type {
 		}
 	}
 
-	for f := t.Type; f != nil && !t.Broke; f = f.Down {
+	for f, it := IterFields(t); f != nil && !t.Broke; f = it.Next() {
 		if f.Broke {
 			t.Broke = true
 		}
@@ -1357,7 +1357,7 @@ func addmethod(sf *Sym, t *Type, local bool, nointerface bool) {
 	}
 
 	if pa.Etype == TSTRUCT {
-		for f := pa.Type; f != nil; f = f.Down {
+		for f, it := IterFields(pa); f != nil; f = it.Next() {
 			if f.Sym == sf {
 				Yyerror("type %v has both field and method named %v", pa, sf)
 				return
@@ -1369,7 +1369,7 @@ func addmethod(sf *Sym, t *Type, local bool, nointerface bool) {
 	n.Type = t
 
 	var d *Type // last found
-	for f := pa.Method; f != nil; f = f.Down {
+	for f, it := IterMethods(pa); f != nil; f = it.Next() {
 		d = f
 		if f.Etype != TFIELD {
 			Fatalf("addmethod: not TFIELD: %v", Tconv(f, obj.FmtLong))

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

@@ -296,7 +296,7 @@ func dumpexporttype(t *Type) {
 	}
 
 	var m []*Type
-	for f := t.Method; f != nil; f = f.Down {
+	for f, it := IterMethods(t); f != nil; f = it.Next() {
 		dumpexporttype(f)
 		m = append(m, f)
 	}
@@ -584,7 +584,7 @@ func dumpasmhdr() {
 				break
 			}
 			fmt.Fprintf(b, "#define %s__size %d\n", t.Sym.Name, int(t.Width))
-			for t = t.Type; t != nil; t = t.Down {
+			for t, it := IterFields(t); t != nil; t = it.Next() {
 				if !isblanksym(t.Sym) {
 					fmt.Fprintf(b, "#define %s_%s %d\n", n.Sym.Name, t.Sym.Name, int(t.Width))
 				}

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

@@ -585,7 +585,7 @@ func typefmt(t *Type, flag int) string {
 	case TINTER:
 		var buf bytes.Buffer
 		buf.WriteString("interface {")
-		for t1 := t.Type; t1 != nil; t1 = t1.Down {
+		for t1, it := IterFields(t); t1 != nil; t1 = it.Next() {
 			buf.WriteString(" ")
 			switch {
 			case t1.Sym == nil:
@@ -663,14 +663,14 @@ func typefmt(t *Type, flag int) string {
 		if t.Funarg {
 			buf.WriteString("(")
 			if fmtmode == FTypeId || fmtmode == FErr { // no argument names on function signature, and no "noescape"/"nosplit" tags
-				for t1 := t.Type; t1 != nil; t1 = t1.Down {
+				for t1, it := IterFields(t); t1 != nil; t1 = it.Next() {
 					buf.WriteString(Tconv(t1, obj.FmtShort))
 					if t1.Down != nil {
 						buf.WriteString(", ")
 					}
 				}
 			} else {
-				for t1 := t.Type; t1 != nil; t1 = t1.Down {
+				for t1, it := IterFields(t); t1 != nil; t1 = it.Next() {
 					buf.WriteString(Tconv(t1, 0))
 					if t1.Down != nil {
 						buf.WriteString(", ")
@@ -680,7 +680,7 @@ func typefmt(t *Type, flag int) string {
 			buf.WriteString(")")
 		} else {
 			buf.WriteString("struct {")
-			for t1 := t.Type; t1 != nil; t1 = t1.Down {
+			for t1, it := IterFields(t); t1 != nil; t1 = it.Next() {
 				buf.WriteString(" ")
 				buf.WriteString(Tconv(t1, obj.FmtLong))
 				if t1.Down != nil {

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

@@ -1242,7 +1242,7 @@ func visitComponents(t *Type, startOffset int64, f func(elem *Type, elemOffset i
 			Fatalf("struct not at offset 0")
 		}
 
-		for field := t.Type; field != nil; field = field.Down {
+		for field, it := IterFields(t); field != nil; field = it.Next() {
 			if field.Etype != TFIELD {
 				Fatalf("bad struct")
 			}

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

@@ -951,7 +951,7 @@ func onebitwalktype1(t *Type, xoffset *int64, bv Bvec) {
 	case TSTRUCT:
 		o := int64(0)
 		var fieldoffset int64
-		for t1 := t.Type; t1 != nil; t1 = t1.Down {
+		for t1, it := IterFields(t); t1 != nil; t1 = it.Next() {
 			fieldoffset = t1.Width
 			*xoffset += fieldoffset - o
 			onebitwalktype1(t1.Type, xoffset, bv)

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

@@ -299,7 +299,7 @@ func methods(t *Type) []*Sig {
 	// make list of methods for t,
 	// generating code if necessary.
 	var ms []*Sig
-	for f := mt.Xmethod; f != nil; f = f.Down {
+	for f, it2 := IterAllMethods(mt); f != nil; f = it2.Next() {
 		if f.Etype != TFIELD {
 			Fatalf("methods: not field %v", f)
 		}

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

@@ -2634,7 +2634,7 @@ func canSSAType(t *Type) bool {
 		if countfield(t) > ssa.MaxStruct {
 			return false
 		}
-		for t1 := t.Type; t1 != nil; t1 = t1.Down {
+		for t1, it := IterFields(t); t1 != nil; t1 = it.Next() {
 			if !canSSAType(t1.Type) {
 				return false
 			}
@@ -5138,7 +5138,7 @@ func fieldIdx(n *Node) int64 {
 	}
 
 	var i int64
-	for t1 := t.Type; t1 != nil; t1 = t1.Down {
+	for t1, it := IterFields(t); t1 != nil; t1 = it.Next() {
 		if t1.Etype != TFIELD {
 			panic("non-TFIELD in TSTRUCT")
 		}

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

@@ -1136,7 +1136,7 @@ func substAny(tp **Type, types *[]*Type) {
 			substAny(t.ResultsP(), types)
 
 		case TSTRUCT:
-			for t = t.Type; t != nil; t = t.Down {
+			for t, it := IterFields(t); t != nil; t = it.Next() {
 				substAny(&t.Type, types)
 			}
 		}
@@ -1219,7 +1219,7 @@ func deep(t *Type) *Type {
 		nt.Type = t.Type.Copy()
 		xt := nt.Type
 
-		for t = t.Type; t != nil; t = t.Down {
+		for t, it := IterFields(t); t != nil; t = it.Next() {
 			xt.Type = deep(t.Type)
 			xt.Down = t.Down.Copy()
 			xt = xt.Down
@@ -1588,7 +1588,7 @@ func lookdot0(s *Sym, t *Type, save **Type, ignorecase bool) int {
 
 	c := 0
 	if u.Etype == TSTRUCT || u.Etype == TINTER {
-		for f := u.Type; f != nil; f = f.Down {
+		for f, it := IterFields(u); f != nil; f = it.Next() {
 			if f.Sym == s || (ignorecase && f.Type.Etype == TFUNC && f.Type.Thistuple > 0 && strings.EqualFold(f.Sym.Name, s.Name)) {
 				if save != nil {
 					*save = f
@@ -1600,7 +1600,7 @@ func lookdot0(s *Sym, t *Type, save **Type, ignorecase bool) int {
 
 	u = methtype(t, 0)
 	if u != nil {
-		for f := u.Method; f != nil; f = f.Down {
+		for f, it := IterMethods(u); f != nil; f = it.Next() {
 			if f.Embedded == 0 && (f.Sym == s || (ignorecase && strings.EqualFold(f.Sym.Name, s.Name))) {
 				if save != nil {
 					*save = f
@@ -1645,7 +1645,7 @@ func adddot1(s *Sym, t *Type, d int, save **Type, ignorecase bool) (c int, more
 		goto out
 	}
 
-	for f := u.Type; f != nil; f = f.Down {
+	for f, it := IterFields(u); f != nil; f = it.Next() {
 		if f.Embedded == 0 || f.Sym == nil {
 			continue
 		}
@@ -1759,7 +1759,7 @@ func expand0(t *Type, followptr bool) {
 
 	if u.Etype == TINTER {
 		var sl *Symlink
-		for f := u.Type; f != nil; f = f.Down {
+		for f, it := IterFields(u); f != nil; f = it.Next() {
 			if f.Sym.Flags&SymUniq != 0 {
 				continue
 			}
@@ -1777,7 +1777,7 @@ func expand0(t *Type, followptr bool) {
 	u = methtype(t, 0)
 	if u != nil {
 		var sl *Symlink
-		for f := u.Method; f != nil; f = f.Down {
+		for f, it := IterMethods(u); f != nil; f = it.Next() {
 			if f.Sym.Flags&SymUniq != 0 {
 				continue
 			}
@@ -1811,7 +1811,7 @@ func expand1(t *Type, top, followptr bool) {
 		goto out
 	}
 
-	for f := u.Type; f != nil; f = f.Down {
+	for f, it := IterFields(u); f != nil; f = it.Next() {
 		if f.Embedded == 0 {
 			continue
 		}
@@ -1833,7 +1833,7 @@ func expandmeth(t *Type) {
 	// mark top-level method symbols
 	// so that expand1 doesn't consider them.
 	var f *Type
-	for f = t.Method; f != nil; f = f.Down {
+	for f, it := IterMethods(t); f != nil; f = it.Next() {
 		f.Sym.Flags |= SymUniq
 	}
 
@@ -1855,7 +1855,7 @@ func expandmeth(t *Type) {
 		}
 	}
 
-	for f = t.Method; f != nil; f = f.Down {
+	for f, it := IterMethods(t); f != nil; f = it.Next() {
 		f.Sym.Flags &^= SymUniq
 	}
 
@@ -2114,9 +2114,8 @@ func implements(t *Type, iface *Type, m **Type, samename **Type, ptr *int) bool
 	// and then do one loop.
 
 	if t.Etype == TINTER {
-		var tm *Type
-		for im := iface.Type; im != nil; im = im.Down {
-			for tm = t.Type; tm != nil; tm = tm.Down {
+		for im, it := IterFields(iface); im != nil; im = it.Next() {
+			for tm, it2 := IterFields(t); tm != nil; tm = it2.Next() {
 				if tm.Sym == im.Sym {
 					if Eqtype(tm.Type, im.Type) {
 						goto found
@@ -2146,7 +2145,7 @@ func implements(t *Type, iface *Type, m **Type, samename **Type, ptr *int) bool
 	var imtype *Type
 	var followptr bool
 	var rcvr *Type
-	for im := iface.Type; im != nil; im = im.Down {
+	for im, it := IterFields(iface); im != nil; im = it.Next() {
 		if im.Broke {
 			continue
 		}

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

@@ -200,7 +200,29 @@ func IterFields(t *Type) (*Type, Iter) {
 	if t.Etype != TSTRUCT && t.Etype != TINTER {
 		Fatalf("IterFields: type %v does not have fields", t)
 	}
-	i := Iter{x: t.Type}
+	return RawIter(t.Type)
+}
+
+// IterMethods returns the first method in type t's method set
+// and an Iter value to continue iterating across the rest.
+// IterMethods does not include promoted methods.
+func IterMethods(t *Type) (*Type, Iter) {
+	// TODO(mdempsky): Validate t?
+	return RawIter(t.Method)
+}
+
+// IterAllMethods returns the first (possibly promoted) method in type t's
+// method set and an Iter value to continue iterating across the rest.
+func IterAllMethods(t *Type) (*Type, Iter) {
+	// TODO(mdempsky): Validate t?
+	return RawIter(t.Xmethod)
+}
+
+// RawIter returns field t and an Iter value to continue iterating across
+// its successor fields. Most code should instead use one of the IterXXX
+// functions above.
+func RawIter(t *Type) (*Type, Iter) {
+	i := Iter{x: t}
 	f := i.Next()
 	return f, i
 }

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

@@ -2372,7 +2372,7 @@ func twoarg(n *Node) bool {
 
 func lookdot1(errnode *Node, s *Sym, t *Type, f *Type, dostrcmp int) *Type {
 	var r *Type
-	for ; f != nil; f = f.Down {
+	for f, it := RawIter(f); f != nil; f = it.Next() {
 		if dostrcmp != 0 && f.Sym.Name == s.Name {
 			return f
 		}
@@ -2577,7 +2577,7 @@ func nokeys(l Nodes) bool {
 }
 
 func hasddd(t *Type) bool {
-	for tl := t.Type; tl != nil; tl = tl.Down {
+	for tl, it := IterFields(t); tl != nil; tl = it.Next() {
 		if tl.Isddd {
 			return true
 		}
@@ -2590,7 +2590,7 @@ func hasddd(t *Type) bool {
 // TODO decide if we want both (for semantic reasons)
 func downcount(t *Type) int {
 	n := 0
-	for tl := t.Type; tl != nil; tl = tl.Down {
+	for tl, it := IterFields(t); tl != nil; tl = it.Next() {
 		n++
 	}
 
@@ -2629,7 +2629,7 @@ func typecheckaste(op Op, call *Node, isddd bool, tstruct *Type, nl Nodes, desc
 
 				tn := n.Type.Type
 				var why string
-				for tl := tstruct.Type; tl != nil; tl = tl.Down {
+				for tl, it2 := IterFields(tstruct); tl != nil; tl = it2.Next() {
 					if tl.Isddd {
 						for ; tn != nil; tn = tn.Down {
 							if assignop(tn.Type, tl.Type.Type, &why) == 0 {
@@ -2691,7 +2691,7 @@ func typecheckaste(op Op, call *Node, isddd bool, tstruct *Type, nl Nodes, desc
 	}
 
 	i = 0
-	for tl := tstruct.Type; tl != nil; tl = tl.Down {
+	for tl, it := IterFields(tstruct); tl != nil; tl = it.Next() {
 		t = tl.Type
 		if tl.Isddd {
 			if isddd {

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

@@ -3083,7 +3083,7 @@ func eqfor(t *Type, needsize *int) *Node {
 
 func countfield(t *Type) int {
 	n := 0
-	for t1 := t.Type; t1 != nil; t1 = t1.Down {
+	for t1, it := IterFields(t); t1 != nil; t1 = it.Next() {
 		n++
 	}
 	return n
@@ -3234,7 +3234,7 @@ func walkcompare(np **Node, init *Nodes) {
 		// Inline comparisons.
 		var li *Node
 		var ri *Node
-		for t1 := t.Type; t1 != nil; t1 = t1.Down {
+		for t1, it := IterFields(t); t1 != nil; t1 = it.Next() {
 			if isblanksym(t1.Sym) {
 				continue
 			}