Fix rewriter to not treat throw as an expression.

Now we can correctly optimize top level code that contains a throw (or
return) as it's last statement.

R=ulan@chromium.org
BUG=v8:2054
TEST=mjsunit/regress/regress-2054

Review URL: https://chromiumcodereview.appspot.com/9969146

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11224 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/rewriter.cc

@@ -111,7 +111,7 @@ void Processor::VisitBlock(Block* node) {
 
 void Processor::VisitExpressionStatement(ExpressionStatement* node) {
   // Rewrite : <x>; -> .result = <x>;
-  if (!is_set_) {
+  if (!is_set_ && !node->expression()->IsThrow()) {
     node->set_expression(SetResult(node->expression()));
     if (!in_try_) is_set_ = true;
   }

test/mjsunit/regress/regress-2054.js

+// Copyright 2012 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.
+
+// Test that we can correctly optimize top level code that contains a
+// throw (or return) as it's last statement.
+
+var N = 1e5;  // Number of iterations that trigger optimization.
+for (var i = 0; i < N; i++) {
+  if (i > N) throw new Error;
+}