Don't eliminate loads with incompatible types or representations.

BUG=346343
LOG=y
R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/179553002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@19536 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/hydrogen-load-elimination.cc

@@ -76,7 +76,9 @@ class HLoadEliminationTable : public ZoneObject {
                FieldOf(l->access()),
                l->object()->ActualValue()->id()));
         HValue* result = load(l);
-        if (result != instr) {
+        if (result != instr &&
+            result->type().Equals(instr->type()) &&
+            result->representation().Equals(instr->representation())) {
           // The load can be replaced with a previous load or a value.
           TRACE(("  replace L%d -> v%d\n", instr->id(), result->id()));
           instr->DeleteAndReplaceWith(result);

test/mjsunit/regress/regress-346343.js

+// Copyright 2014 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
+
+function f(o) {
+  for (var i = 1; i < 2; ++i) {
+    var y = o.y;
+  }
+}
+f({y:1.1});
+f({y:1.1});
+
+function g(x) { f({z:x}); }
+g(1);
+g(2);
+%OptimizeFunctionOnNextCall(g);
+g(1);