Fix bug in static type inference for loops.

Review URL: http://codereview.chromium.org/140058


git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2236 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/ia32/virtual-frame-ia32.cc

@@ -220,7 +220,9 @@ void VirtualFrame::MakeMergable() {
       }
       // No need to set the copied flag---there are no copies of
       // copies or constants so the original was not copied.
-      elements_[i].set_static_type(element.static_type());
+
+      // Backwards jump targets can never know the type of a value.
+      elements_[i].set_static_type(StaticType::unknown());
     } else {
       // Clear the copy flag of non-constant, non-copy elements above
       // the high water mark.  They cannot be copied because copes are

test/mjsunit/regress/regress-1919169.js

+// Copyright 2008 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.
+
+
+function test() {
+ var s2 = "s2";
+ for (var i = 0; i < 2; i++) {
+   // Crashes in round i==1 with IllegalAccess in %StringAdd(x,y)
+   var res = 1 + s2;  
+   s2 = 2;
+ }
+}
+
+// Crash does not occur when code is run at the top level.
+test();
+