Fix load elimination: can only .Equals() GVN-able instructions.

BUG=
R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/95193002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@18133 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/hydrogen-load-elimination.cc

@@ -349,7 +349,9 @@ class HLoadEliminationTable : public ZoneObject {
 
   bool Equal(HValue* a, HValue* b) {
     if (a == b) return true;
-    if (a != NULL && b != NULL) return a->Equals(b);
+    if (a != NULL && b != NULL && a->CheckFlag(HValue::kUseGVN)) {
+      return a->Equals(b);
+    }
     return false;
   }
 

test/mjsunit/compiler/load-elimination-params.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
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// 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 test_params1(a, b) {
+  var i = a.x;
+  var j = a.x;
+  var k = b.x;
+  var l = b.x;
+  return i + j + k + l;
+}
+
+assertEquals(14, test_params1(new B(3, 4), new B(4, 5)));
+assertEquals(110, test_params1(new B(11, 7), new B(44, 8)));
+
+%OptimizeFunctionOnNextCall(test_params1);
+
+assertEquals(6, test_params1(new B(1, 7), new B(2, 8)));
+
+function test_params2(a, b) {
+  var o = new B(a + 1, b);
+  o.x = a;
+  var i = o.x;
+  o.x = a;
+  var j = o.x;
+  o.x = b;
+  var k = o.x;
+  o.x = b;
+  var l = o.x;
+  return i + j + k + l;
+}
+
+assertEquals(14, test_params2(3, 4));
+assertEquals(110, test_params2(11, 44));
+
+%OptimizeFunctionOnNextCall(test_params2);
+
+assertEquals(6, test_params2(1, 2));