Check for phi-uses of arguments object before eliminating dead phi's.

test/mjsunit/regress/regress-1582.js

Index: test/mjsunit/regress/regress-1582.js
===================================================================
--- test/mjsunit/regress/regress-1582.js	(revision 0)
+++ test/mjsunit/regress/regress-1582.js	(revision 0)
@@ -0,0 +1,47 @@
+// Copyright 2011 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(restIsArray, rest) {
+  var arr;
+  if (typeof rest === "object" && (rest instanceof Array)) {
+    arr = rest;
+  } else {
+    arr = arguments;
+  }
+  var i = arr.length;
+  while (--i >= 0) arr[i];
+  var arrIsArguments = (arr[1] !== rest);
+  assertEquals(restIsArray, arrIsArguments);
+}
+
+f(false, 'b', 'c');
+f(false, 'b', 'c');
+f(false, 'b', 'c');
+%OptimizeFunctionOnNextCall(f);
+f(true, ['b', 'c']);