[dev.regabi] cmd/compile: separate range stmt Vars to Key, Value nodes

Passes buildall w/ toolstash -cmp.

Change-Id: I9738fcabc8ebf3afa34d102afadf1b474b50db35
Reviewed-on: https://go-review.googlesource.com/c/go/+/279435
Trust: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>

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

@@ -347,21 +347,19 @@ func (e *escape) stmt(n ir.Node) {
 		e.loopDepth--
 
 	case ir.ORANGE:
-		// for List = range Right { Nbody }
+		// for Key, Value = range X { Body }
 		n := n.(*ir.RangeStmt)
 		e.loopDepth++
-		ks := e.addrs(n.Vars)
+		e.addr(n.Key)
+		k := e.addr(n.Value)
 		e.block(n.Body)
 		e.loopDepth--
 
-		// Right is evaluated outside the loop.
-		k := e.discardHole()
-		if len(ks) >= 2 {
+		// X is evaluated outside the loop.
 		if n.X.Type().IsArray() {
-				k = ks[1].note(n, "range")
+			k = k.note(n, "range")
 		} else {
-				k = ks[1].deref(n, "range-deref")
-			}
+			k = k.deref(n, "range-deref")
 		}
 		e.expr(e.later(k), n.X)
 

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

@@ -444,12 +444,15 @@ func stmtFmt(n Node, s fmt.State) {
 			break
 		}
 
-		if len(n.Vars) == 0 {
-			fmt.Fprintf(s, "for range %v { %v }", n.X, n.Body)
-			break
+		fmt.Fprint(s, "for")
+		if n.Key != nil {
+			fmt.Fprintf(s, " %v", n.Key)
+			if n.Value != nil {
+				fmt.Fprintf(s, ", %v", n.Value)
 			}
-
-		fmt.Fprintf(s, "for %.v = range %v { %v }", n.Vars, n.X, n.Body)
+			fmt.Fprint(s, " =")
+		}
+		fmt.Fprintf(s, " range %v { %v }", n.X, n.Body)
 
 	case OSELECT:
 		n := n.(*SelectStmt)

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

@@ -724,22 +724,23 @@ func (n *RangeStmt) Format(s fmt.State, verb rune) { FmtNode(n, s, verb) }
 func (n *RangeStmt) copy() Node {
 	c := *n
 	c.init = c.init.Copy()
-	c.Vars = c.Vars.Copy()
 	c.Body = c.Body.Copy()
 	return &c
 }
 func (n *RangeStmt) doChildren(do func(Node) error) error {
 	var err error
 	err = maybeDoList(n.init, err, do)
-	err = maybeDoList(n.Vars, err, do)
 	err = maybeDo(n.X, err, do)
+	err = maybeDo(n.Key, err, do)
+	err = maybeDo(n.Value, err, do)
 	err = maybeDoList(n.Body, err, do)
 	return err
 }
 func (n *RangeStmt) editChildren(edit func(Node) Node) {
 	editList(n.init, edit)
-	editList(n.Vars, edit)
 	n.X = maybeEdit(n.X, edit)
+	n.Key = maybeEdit(n.Key, edit)
+	n.Value = maybeEdit(n.Value, edit)
 	editList(n.Body, edit)
 }
 

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

@@ -290,25 +290,24 @@ func NewLabelStmt(pos src.XPos, label *types.Sym) *LabelStmt {
 
 func (n *LabelStmt) Sym() *types.Sym { return n.Label }
 
-// A RangeStmt is a range loop: for Vars = range X { Stmts }
-// Op can be OFOR or OFORUNTIL (!Cond).
+// A RangeStmt is a range loop: for Key, Value = range X { Body }
 type RangeStmt struct {
 	miniStmt
 	Label    *types.Sym
-	Vars     Nodes // TODO(rsc): Replace with Key, Value Node
 	Def      bool
 	X        Node
+	Key      Node
+	Value    Node
 	Body     Nodes
 	HasBreak bool
 	typ      *types.Type // TODO(rsc): Remove - use X.Type() instead
 	Prealloc *Name
 }
 
-func NewRangeStmt(pos src.XPos, vars []Node, x Node, body []Node) *RangeStmt {
-	n := &RangeStmt{X: x}
+func NewRangeStmt(pos src.XPos, key, value, x Node, body []Node) *RangeStmt {
+	n := &RangeStmt{X: x, Key: key, Value: value}
 	n.pos = pos
 	n.op = ORANGE
-	n.Vars.Set(vars)
 	n.Body.Set(body)
 	return n
 }

src/cmd/compile/internal/noder/noder.go

@@ -1172,10 +1172,14 @@ func (p *noder) forStmt(stmt *syntax.ForStmt) ir.Node {
 			panic("unexpected RangeClause")
 		}
 
-		n := ir.NewRangeStmt(p.pos(r), nil, p.expr(r.X), nil)
+		n := ir.NewRangeStmt(p.pos(r), nil, nil, p.expr(r.X), nil)
 		if r.Lhs != nil {
 			n.Def = r.Def
-			n.Vars.Set(p.assignList(r.Lhs, n, n.Def))
+			lhs := p.assignList(r.Lhs, n, n.Def)
+			n.Key = lhs[0]
+			if len(lhs) > 1 {
+				n.Value = lhs[1]
+			}
 		}
 		n.Body.Set(p.blockStmt(stmt.Body))
 		p.closeAnotherScope()

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

@@ -1143,7 +1143,7 @@ func (w *exportWriter) stmt(n ir.Node) {
 		n := n.(*ir.RangeStmt)
 		w.op(ir.ORANGE)
 		w.pos(n.Pos())
-		w.stmtList(n.Vars)
+		w.exprsOrNil(n.Key, n.Value)
 		w.expr(n.X)
 		w.stmtList(n.Body)
 

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

@@ -1028,7 +1028,9 @@ func (r *importReader) node() ir.Node {
 		return ir.NewForStmt(pos, init, cond, post, r.stmtList())
 
 	case ir.ORANGE:
-		return ir.NewRangeStmt(r.pos(), r.stmtList(), r.expr(), r.stmtList())
+		pos := r.pos()
+		k, v := r.exprsOrNil()
+		return ir.NewRangeStmt(pos, k, v, r.expr(), r.stmtList())
 
 	case ir.OSELECT:
 		pos := r.pos()

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

@@ -19,19 +19,18 @@ func typecheckrangeExpr(n *ir.RangeStmt) {
 		return
 	}
 	// delicate little dance.  see typecheckas2
-	ls := n.Vars
-	for i1, n1 := range ls {
-		if !ir.DeclaredBy(n1, n) {
-			ls[i1] = AssignExpr(ls[i1])
+	if n.Key != nil && !ir.DeclaredBy(n.Key, n) {
+		n.Key = AssignExpr(n.Key)
 	}
+	if n.Value != nil && !ir.DeclaredBy(n.Value, n) {
+		n.Value = AssignExpr(n.Value)
 	}
-
 	if t.IsPtr() && t.Elem().IsArray() {
 		t = t.Elem()
 	}
 	n.SetType(t)
 
-	var t1, t2 *types.Type
+	var tk, tv *types.Type
 	toomany := false
 	switch t.Kind() {
 	default:
@@ -39,12 +38,12 @@ func typecheckrangeExpr(n *ir.RangeStmt) {
 		return
 
 	case types.TARRAY, types.TSLICE:
-		t1 = types.Types[types.TINT]
-		t2 = t.Elem()
+		tk = types.Types[types.TINT]
+		tv = t.Elem()
 
 	case types.TMAP:
-		t1 = t.Key()
-		t2 = t.Elem()
+		tk = t.Key()
+		tv = t.Elem()
 
 	case types.TCHAN:
 		if !t.ChanDir().CanRecv() {
@@ -52,61 +51,35 @@ func typecheckrangeExpr(n *ir.RangeStmt) {
 			return
 		}
 
-		t1 = t.Elem()
-		t2 = nil
-		if len(n.Vars) == 2 {
+		tk = t.Elem()
+		tv = nil
+		if n.Value != nil {
 			toomany = true
 		}
 
 	case types.TSTRING:
-		t1 = types.Types[types.TINT]
-		t2 = types.RuneType
+		tk = types.Types[types.TINT]
+		tv = types.RuneType
 	}
 
-	if len(n.Vars) > 2 || toomany {
+	if toomany {
 		base.ErrorfAt(n.Pos(), "too many variables in range")
 	}
 
-	var v1, v2 ir.Node
-	if len(n.Vars) != 0 {
-		v1 = n.Vars[0]
-	}
-	if len(n.Vars) > 1 {
-		v2 = n.Vars[1]
-	}
-
-	// this is not only an optimization but also a requirement in the spec.
-	// "if the second iteration variable is the blank identifier, the range
-	// clause is equivalent to the same clause with only the first variable
-	// present."
-	if ir.IsBlank(v2) {
-		if v1 != nil {
-			n.Vars = []ir.Node{v1}
-		}
-		v2 = nil
-	}
-
-	if v1 != nil {
-		if ir.DeclaredBy(v1, n) {
-			v1.SetType(t1)
-		} else if v1.Type() != nil {
-			if op, why := assignop(t1, v1.Type()); op == ir.OXXX {
-				base.ErrorfAt(n.Pos(), "cannot assign type %v to %L in range%s", t1, v1, why)
+	do := func(nn ir.Node, t *types.Type) {
+		if nn != nil {
+			if ir.DeclaredBy(nn, n) {
+				nn.SetType(t)
+			} else if nn.Type() != nil {
+				if op, why := assignop(t, nn.Type()); op == ir.OXXX {
+					base.ErrorfAt(n.Pos(), "cannot assign type %v to %L in range%s", t, nn, why)
 				}
 			}
-		checkassign(n, v1)
-	}
-
-	if v2 != nil {
-		if ir.DeclaredBy(v2, n) {
-			v2.SetType(t2)
-		} else if v2.Type() != nil {
-			if op, why := assignop(t2, v2.Type()); op == ir.OXXX {
-				base.ErrorfAt(n.Pos(), "cannot assign type %v to %L in range%s", t2, v2, why)
+			checkassign(n, nn)
 		}
 	}
-		checkassign(n, v2)
-	}
+	do(n.Key, tk)
+	do(n.Value, tv)
 }
 
 // type check assignment.
@@ -399,11 +372,11 @@ func tcRange(n *ir.RangeStmt) {
 
 	// second half of dance, the first half being typecheckrangeExpr
 	n.SetTypecheck(1)
-	ls := n.Vars
-	for i1, n1 := range ls {
-		if n1.Typecheck() == 0 {
-			ls[i1] = AssignExpr(ls[i1])
+	if n.Key != nil && n.Key.Typecheck() == 0 {
+		n.Key = AssignExpr(n.Key)
 	}
+	if n.Value != nil && n.Value.Typecheck() == 0 {
+		n.Value = AssignExpr(n.Value)
 	}
 
 	decldepth++

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

@@ -848,7 +848,7 @@ func (o *orderState) stmt(n ir.Node) {
 			base.Fatalf("order.stmt range %v", n.Type())
 
 		case types.TARRAY, types.TSLICE:
-			if len(n.Vars) < 2 || ir.IsBlank(n.Vars[1]) {
+			if n.Value == nil || ir.IsBlank(n.Value) {
 				// for i := range x will only use x once, to compute len(x).
 				// No need to copy it.
 				break
@@ -887,7 +887,8 @@ func (o *orderState) stmt(n ir.Node) {
 			// hiter contains pointers and needs to be zeroed.
 			n.Prealloc = o.newTemp(reflectdata.MapIterType(n.Type()), true)
 		}
-		o.exprListInPlace(n.Vars)
+		n.Key = o.exprInPlace(n.Key)
+		n.Value = o.exprInPlace(n.Value)
 		if orderBody {
 			orderBlock(&n.Body, o.free)
 		}

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

@@ -61,15 +61,7 @@ func walkRange(nrange *ir.RangeStmt) ir.Node {
 	a := nrange.X
 	lno := ir.SetPos(a)
 
-	var v1, v2 ir.Node
-	l := len(nrange.Vars)
-	if l > 0 {
-		v1 = nrange.Vars[0]
-	}
-
-	if l > 1 {
-		v2 = nrange.Vars[1]
-	}
+	v1, v2 := nrange.Key, nrange.Value
 
 	if ir.IsBlank(v2) {
 		v2 = nil
@@ -343,15 +335,11 @@ func isMapClear(n *ir.RangeStmt) bool {
 		return false
 	}
 
-	if n.Op() != ir.ORANGE || n.Type().Kind() != types.TMAP || len(n.Vars) != 1 {
-		return false
-	}
-
-	k := n.Vars[0]
-	if k == nil || ir.IsBlank(k) {
+	if n.Op() != ir.ORANGE || n.Type().Kind() != types.TMAP || n.Key == nil || n.Value != nil {
 		return false
 	}
 
+	k := n.Key
 	// Require k to be a new variable name.
 	if !ir.DeclaredBy(k, n) {
 		return false