Fix pattern detection for replacing shifts by rotation.

BUG=2499
R=svenpanne@chromium.org

Review URL: https://chromiumcodereview.appspot.com/12047015
Patch from Hirofumi Mako <mkhrfm@gmail.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13464 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/hydrogen.cc

@@ -8464,6 +8464,7 @@ static bool ShiftAmountsAllowReplaceByRotate(HValue* sa,
                                              HValue* const32_minus_sa) {
   if (!const32_minus_sa->IsSub()) return false;
   HSub* sub = HSub::cast(const32_minus_sa);
+  if (sa != sub->right()) return false;
   HValue* const32 = sub->left();
   if (!const32->IsConstant() ||
       HConstant::cast(const32)->Integer32Value() != 32) {
@@ -8492,6 +8493,7 @@ bool HOptimizedGraphBuilder::MatchRotateRight(HValue* left,
   } else {
     return false;
   }
+  if (shl->left() != shr->left()) return false;
 
   if (!ShiftAmountsAllowReplaceByRotate(shl->right(), shr->right()) &&
       !ShiftAmountsAllowReplaceByRotate(shr->right(), shl->right())) {

test/mjsunit/regress/regress-2499.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
+
+function foo(word, nBits) {
+  return (word[1] >>> nBits) | (word[0] << (32 - nBits));
+}
+
+word = [0x1001, 0];
+
+var expected = foo(word, 1);
+foo(word, 1);
+%OptimizeFunctionOnNextCall(foo);
+var optimized = foo(word, 1);
+assertEquals(expected, optimized)