cmd/compile: add convnop helper function

Like the conv helper function but for creating OCONVNOP nodes
instead of OCONV nodes.

passes toolstash -cmp

Change-Id: Ib93ffe66590ebaa2b4fa552c81f1a2902e789d8e
Reviewed-on: https://go-review.googlesource.com/112597
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

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

@@ -382,10 +382,7 @@ func walkclosure(clo *Node, init *Nodes) *Node {
 	clos.List.Set(append([]*Node{nod(OCFUNC, xfunc.Func.Nname, nil)}, clo.Func.Enter.Slice()...))
 
 	// Force type conversion from *struct to the func type.
-	clos = nod(OCONVNOP, clos, nil)
-	clos.Type = clo.Type
-
-	clos = typecheck(clos, Erv)
+	clos = convnop(clos, clo.Type)
 
 	// typecheck will insert a PTRLIT node under CONVNOP,
 	// tag it with escape analysis result.
@@ -511,10 +508,7 @@ func walkpartialcall(n *Node, init *Nodes) *Node {
 	clos.List.Append(n.Left)
 
 	// Force type conversion from *struct to the func type.
-	clos = nod(OCONVNOP, clos, nil)
-	clos.Type = n.Type
-
-	clos = typecheck(clos, Erv)
+	clos = convnop(clos, n.Type)
 
 	// typecheck will insert a PTRLIT node under CONVNOP,
 	// tag it with escape analysis result.

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

@@ -580,8 +580,7 @@ func arrayClear(n, v1, v2, a *Node) bool {
 	tmp := nod(OINDEX, a, nodintconst(0))
 	tmp.SetBounded(true)
 	tmp = nod(OADDR, tmp, nil)
-	tmp = nod(OCONVNOP, tmp, nil)
-	tmp.Type = types.Types[TUNSAFEPTR]
+	tmp = convnop(tmp, types.Types[TUNSAFEPTR])
 	n.Nbody.Append(nod(OAS, hp, tmp))
 
 	// hn = len(a) * sizeof(elem(a))

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

@@ -316,13 +316,11 @@ func walkselectcases(cases *Nodes) []*Node {
 
 		setField("kind", nodintconst(kind))
 		if c != nil {
-			c = nod(OCONVNOP, c, nil)
-			c.Type = types.Types[TUNSAFEPTR]
+			c = convnop(c, types.Types[TUNSAFEPTR])
 			setField("c", c)
 		}
 		if elem != nil {
-			elem = nod(OCONVNOP, elem, nil)
-			elem.Type = types.Types[TUNSAFEPTR]
+			elem = convnop(elem, types.Types[TUNSAFEPTR])
 			setField("elem", elem)
 		}
 
@@ -375,10 +373,9 @@ func walkselectcases(cases *Nodes) []*Node {
 
 // bytePtrToIndex returns a Node representing "(*byte)(&n[i])".
 func bytePtrToIndex(n *Node, i int64) *Node {
-	s := nod(OCONVNOP, nod(OADDR, nod(OINDEX, n, nodintconst(i)), nil), nil)
-	s.Type = types.NewPtr(types.Types[TUINT8])
-	s = typecheck(s, Erv)
-	return s
+	s := nod(OADDR, nod(OINDEX, n, nodintconst(i)), nil)
+	t := types.NewPtr(types.Types[TUINT8])
+	return convnop(s, t)
 }
 
 var scase *types.Type

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

@@ -1674,8 +1674,7 @@ func genwrapper(rcvr *types.Type, method *types.Field, newnam *types.Sym) {
 		if !dotlist[0].field.Type.IsPtr() {
 			dot = nod(OADDR, dot, nil)
 		}
-		as := nod(OAS, nthis, nod(OCONVNOP, dot, nil))
-		as.Right.Type = rcvr
+		as := nod(OAS, nthis, convnop(dot, rcvr))
 		fn.Nbody.Append(as)
 		fn.Nbody.Append(nodSym(ORETJMP, nil, methodSym(methodrcvr, method.Sym)))
 	} else {

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

@@ -1506,9 +1506,7 @@ opswitch:
 				a = typecheck(a, Etop)
 				a = walkexpr(a, init)
 				init.Append(a)
-				n = nod(OCONVNOP, h, nil)
-				n.Type = t
-				n = typecheck(n, Erv)
+				n = convnop(h, t)
 			} else {
 				// Call runtime.makehmap to allocate an
 				// hmap on the heap and initialize hmap's hash0 field.
@@ -2029,8 +2027,7 @@ func ascompatte(call *Node, isddd bool, lhs *types.Type, rhs []*Node, fp int, in
 		// optimization - can do block copy
 		if eqtypenoname(rhs[0].Type, lhs) {
 			nl := nodarg(lhs, fp)
-			nr := nod(OCONVNOP, rhs[0], nil)
-			nr.Type = nl.Type
+			nr := convnop(rhs[0], nl.Type)
 			n := convas(nod(OAS, nl, nr), init)
 			n.SetTypecheck(1)
 			return []*Node{n}
@@ -2748,6 +2745,15 @@ func conv(n *Node, t *types.Type) *Node {
 	return n
 }
 
+// convnop converts node n to type t using the OCONVNOP op
+// and typechecks the result with Erv.
+func convnop(n *Node, t *types.Type) *Node {
+	n = nod(OCONVNOP, n, nil)
+	n.Type = t
+	n = typecheck(n, Erv)
+	return n
+}
+
 // byteindex converts n, which is byte-sized, to a uint8.
 // We cannot use conv, because we allow converting bool to uint8 here,
 // which is forbidden in user code.
@@ -3157,8 +3163,7 @@ func extendslice(n *Node, init *Nodes) *Node {
 	hp := nod(OINDEX, s, nod(OLEN, l1, nil))
 	hp.SetBounded(true)
 	hp = nod(OADDR, hp, nil)
-	hp = nod(OCONVNOP, hp, nil)
-	hp.Type = types.Types[TUNSAFEPTR]
+	hp = convnop(hp, types.Types[TUNSAFEPTR])
 
 	// hn := l2 * sizeof(elem(s))
 	hn := nod(OMUL, l2, nodintconst(elemtype.Width))