Also delete force representations that have no uses.

BUG=
R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/187773002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@19683 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/hydrogen-representation-changes.cc

@@ -78,7 +78,10 @@ void HRepresentationChangesPhase::InsertRepresentationChangesForValue(
     HValue* value) {
   Representation r = value->representation();
   if (r.IsNone()) return;
-  if (value->HasNoUses()) return;
+  if (value->HasNoUses()) {
+    if (value->IsForceRepresentation()) value->DeleteAndReplaceWith(NULL);
+    return;
+  }
 
   for (HUseIterator it(value->uses()); !it.Done(); it.Advance()) {
     HValue* use_value = it.value();

test/mjsunit/regress/regress-force-representation.js

+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --allow-natives-syntax
+
+function optimize(crankshaft_test) {
+  crankshaft_test();
+  crankshaft_test();
+  %OptimizeFunctionOnNextCall(crankshaft_test);
+  crankshaft_test();
+}
+
+function f() {
+  var v1 = 0;
+  var v2 = -0;
+  var t = v2++;
+  v2++;
+  return Math.max(v2++, v1++);
+}
+
+optimize(f);