Do not remove HAdd with zero if the other operand is a double.

The other operand might be minus zero, and -0 + 0 = +0

R=svenpanne@chromium.org
BUG=

Review URL: https://codereview.chromium.org/52173003

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@17432 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/hydrogen-instructions.cc

@@ -1255,8 +1255,15 @@ static bool IsIdentityOperation(HValue* arg1, HValue* arg2, int32_t identity) {
 
 
 HValue* HAdd::Canonicalize() {
-  if (IsIdentityOperation(left(), right(), 0)) return left();
-  if (IsIdentityOperation(right(), left(), 0)) return right();
+  // Adding 0 is an identity operation except in case of -0: -0 + 0 = +0
+  if (IsIdentityOperation(left(), right(), 0) &&
+      !left()->representation().IsDouble()) {  // Left could be -0.
+    return left();
+  }
+  if (IsIdentityOperation(right(), left(), 0) &&
+      !left()->representation().IsDouble()) {  // Right could be -0.
+    return right();
+  }
   return this;
 }
 

test/mjsunit/regress/regress-add-minus-zero.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
+
+var o = { a: 0 };
+
+function f(x) { return -o.a + 0; };
+
+assertEquals("Infinity", String(1/f()));
+assertEquals("Infinity", String(1/f()));
+%OptimizeFunctionOnNextCall(f);
+assertEquals("Infinity", String(1/f()));
+