Make HCapturedObjects non-deletable for DCE.

R=jkummerow@chromium.org
BUG=v8:2987
TEST=mjsunit/regress/regress-2987

Review URL: https://codereview.chromium.org/64433002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@17569 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/hydrogen-instructions.h

@@ -3259,9 +3259,6 @@ class HDematerializedObject : public HInstruction {
 
   // List of values tracked by this marker.
   ZoneList<HValue*> values_;
-
- private:
-  virtual bool IsDeletable() const V8_FINAL V8_OVERRIDE { return true; }
 };
 
 
@@ -3289,6 +3286,8 @@ class HArgumentsObject V8_FINAL : public HDematerializedObject {
     set_representation(Representation::Tagged());
     SetFlag(kIsArguments);
   }
+
+  virtual bool IsDeletable() const V8_FINAL V8_OVERRIDE { return true; }
 };
 
 
@@ -3325,6 +3324,11 @@ class HCapturedObject V8_FINAL : public HDematerializedObject {
 
  private:
   int capture_id_;
+
+  // Note that we cannot DCE captured objects as they are used to replay
+  // the environment. This method is here as an explicit reminder.
+  // TODO(mstarzinger): Turn HSimulates into full snapshots maybe?
+  virtual bool IsDeletable() const V8_FINAL V8_OVERRIDE { return false; }
 };
 
 

test/mjsunit/regress/regress-2987.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 --dead-code-elimination
+
+// This tests that stores on captured objects are correctly tracked even
+// when DCE is enabled. We cannot delete simulations of captured objects
+// that are still needed to replay the environment correctly.
+
+function constructor() {
+  this.x = 0;
+}
+
+var deopt = { deopt:false };
+function boogeyman(mode, value) {
+  var object = new constructor();
+  if (mode) {
+    object.x = 1;
+  } else {
+    object.x = 2;
+  }
+  deopt.deopt;
+  assertEquals(value, object.x);
+}
+
+boogeyman(true, 1);
+boogeyman(true, 1);
+boogeyman(false, 2);
+boogeyman(false, 2);
+%OptimizeFunctionOnNextCall(boogeyman);
+boogeyman(false, 2);
+delete deopt.deopt;
+boogeyman(false, 2);