Improve load elimination handling of transitioning stores.

test/mjsunit/compiler/load-elimination.js

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 17 matching lines @@
 // Flags: --allow-natives-syntax --load-elimination
 
 // Test local load elimination of redundant loads and stores.
 
 function B(x, y) {
   this.x = x;
   this.y = y;
   return this;
 }
 
+function C() {
+}
+
 function test_load() {
   var a = new B(1, 2);
   return a.x + a.x + a.x + a.x;
 }
 
 function test_store_load() {
   var a = new B(1, 2);
   a.x = 4;
   var f = a.x;
   a.x = 5;
   var g = a.x;
   a.x = 6;
   var h = a.x;
   a.x = 7;
   return f + g + h + a.x;
 }
 
 function test_nonaliasing_store1() {
   var a = new B(2, 3), b = new B(3, 4);
   b.x = 4;
   var f = a.x;
   b.x = 5;
   var g = a.x;
   b.x = 6;
   var h = a.x;
   b.x = 7;
   return f + g + h + a.x;
 }
 
+function test_transitioning_store1() {
+  var a = new B(2, 3);
+  var f = a.x, g = a.y;
+  var b = new B(3, 4);
+  return a.x + a.y;
+}
+
+function test_transitioning_store2() {
+  var b = new C();
+  var a = new B(-1, 5);
+  var f = a.x, g = a.y;
+  b.x = 9;
+  b.y = 11;
+  return a.x + a.y;
+}
+
 function killall() {
   try { } catch(e) { }
 }
 
 %NeverOptimizeFunction(killall);
 
 function test_store_load_kill() {
   var a = new B(1, 2);
   a.x = 4;
   var f = a.x;
@@ skipping 18 matching lines @@
 function test(x, f) {
   assertEquals(x, f());
   assertEquals(x, f());
   %OptimizeFunctionOnNextCall(f);
   assertEquals(x, f());
 }
 
 test(4, test_load);
 test(22, test_store_load);
 test(8, test_nonaliasing_store1);
+test(5, test_transitioning_store1);
+test(4, test_transitioning_store2);
 test(22, test_store_load_kill);
 test(7, test_store_store);