cmd/compile/internal/walk: merge operations

Change-Id: I018872da519dfb4aa6c252ea28fc09289c2d9711
GitHub-Last-Rev: 5969776197
GitHub-Pull-Request: golang/go#45795
Reviewed-on: https://go-review.googlesource.com/c/go/+/313550
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Keith Randall <khr@golang.org>

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

@@ -118,9 +118,7 @@ func walkRange(nrange *ir.RangeStmt) ir.Node {
 			tmp.SetBounded(true)
 			// Use OAS2 to correctly handle assignments
 			// of the form "v1, a[v1] := range".
-			a := ir.NewAssignListStmt(base.Pos, ir.OAS2, nil, nil)
+			a := ir.NewAssignListStmt(base.Pos, ir.OAS2, []ir.Node{v1, v2}, []ir.Node{hv1, tmp})
-			a.Lhs = []ir.Node{v1, v2}
-			a.Rhs = []ir.Node{hv1, tmp}
 			body = []ir.Node{a}
 			break
 		}
@@ -148,9 +146,7 @@ func walkRange(nrange *ir.RangeStmt) ir.Node {
 
 		// Use OAS2 to correctly handle assignments
 		// of the form "v1, a[v1] := range".
-		a := ir.NewAssignListStmt(base.Pos, ir.OAS2, nil, nil)
+		a := ir.NewAssignListStmt(base.Pos, ir.OAS2, []ir.Node{v1, v2}, []ir.Node{hv1, ir.NewStarExpr(base.Pos, hp)})
-		a.Lhs = []ir.Node{v1, v2}
-		a.Rhs = []ir.Node{hv1, ir.NewStarExpr(base.Pos, hp)}
 		body = append(body, a)
 
 		// Advance pointer as part of the late increment.
@@ -190,9 +186,7 @@ func walkRange(nrange *ir.RangeStmt) ir.Node {
 			body = []ir.Node{ir.NewAssignStmt(base.Pos, v1, key)}
 		} else {
 			elem := ir.NewStarExpr(base.Pos, ir.NewSelectorExpr(base.Pos, ir.ODOT, hit, elemsym))
-			a := ir.NewAssignListStmt(base.Pos, ir.OAS2, nil, nil)
+			a := ir.NewAssignListStmt(base.Pos, ir.OAS2, []ir.Node{v1, v2}, []ir.Node{key, elem})
-			a.Lhs = []ir.Node{v1, v2}
-			a.Rhs = []ir.Node{key, elem}
 			body = []ir.Node{a}
 		}
 
@@ -208,10 +202,10 @@ func walkRange(nrange *ir.RangeStmt) ir.Node {
 		hb := typecheck.Temp(types.Types[types.TBOOL])
 
 		nfor.Cond = ir.NewBinaryExpr(base.Pos, ir.ONE, hb, ir.NewBool(false))
-		a := ir.NewAssignListStmt(base.Pos, ir.OAS2RECV, nil, nil)
+		lhs := []ir.Node{hv1, hb}
+		rhs := []ir.Node{ir.NewUnaryExpr(base.Pos, ir.ORECV, ha)}
+		a := ir.NewAssignListStmt(base.Pos, ir.OAS2RECV, lhs, rhs)
 		a.SetTypecheck(1)
-		a.Lhs = []ir.Node{hv1, hb}
-		a.Rhs = []ir.Node{ir.NewUnaryExpr(base.Pos, ir.ORECV, ha)}
 		nfor.Cond = ir.InitExpr([]ir.Node{a}, nfor.Cond)
 		if v1 == nil {
 			body = nil
@@ -270,24 +264,18 @@ func walkRange(nrange *ir.RangeStmt) ir.Node {
 		nif.Body = []ir.Node{ir.NewAssignStmt(base.Pos, hv1, ir.NewBinaryExpr(base.Pos, ir.OADD, hv1, ir.NewInt(1)))}
 
 		// } else {
-		eif := ir.NewAssignListStmt(base.Pos, ir.OAS2, nil, nil)
-
 		// hv2, hv1 = decoderune(ha, hv1)
-		eif.Lhs = []ir.Node{hv2, hv1}
 		fn := typecheck.LookupRuntime("decoderune")
-		var fnInit ir.Nodes
+		call := mkcall1(fn, fn.Type().Results(), &nif.Else, ha, hv1)
-		eif.Rhs = []ir.Node{mkcall1(fn, fn.Type().Results(), &fnInit, ha, hv1)}
+		a := ir.NewAssignListStmt(base.Pos, ir.OAS2, []ir.Node{hv2, hv1}, []ir.Node{call})
-		fnInit.Append(eif)
+		nif.Else.Append(a)
-		nif.Else = fnInit
 
 		body = append(body, nif)
 
 		if v1 != nil {
 			if v2 != nil {
 				// v1, v2 = hv1t, hv2
-				a := ir.NewAssignListStmt(base.Pos, ir.OAS2, nil, nil)
+				a := ir.NewAssignListStmt(base.Pos, ir.OAS2, []ir.Node{v1, v2}, []ir.Node{hv1t, hv2})
-				a.Lhs = []ir.Node{v1, v2}
-				a.Rhs = []ir.Node{hv1t, hv2}
 				body = append(body, a)
 			} else {
 				// v1 = hv1t