Revision: 5927
Author: [email protected]
Date: Tue Dec 7 04:07:40 2010
Log: Be more careful about exiting inlined functions in a test context.
When falling off the end of a function inlined in a test context, we cannot
constant fold the test of undefined away. The graph builder assumes that
control flow always reaches both branches of a test.
Instead, explicitly test and branch on "undefined". Introduce a pair of
empty blocks to hold the necessary LeaveInlined instructions.
Review URL: http://codereview.chromium.org/5566005
http://code.google.com/p/v8/source/detail?r=5927
Added:
/branches/bleeding_edge/test/mjsunit/compiler/regress-3260426.js
Modified:
/branches/bleeding_edge/src/hydrogen.cc
=======================================
--- /dev/null
+++ /branches/bleeding_edge/test/mjsunit/compiler/regress-3260426.js Tue
Dec 7 04:07:40 2010
@@ -0,0 +1,36 @@
+// Copyright 2010 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.
+
+// Falling off the end of a function returns the undefined value
+// (false in a test context). This should happen even when inlined
+// (e.g., if --always-opt) and when it is the only exit from the
+// function.
+function always_false() {}
+function test() { return always_false() ? 0 : 1; }
+
+assertEquals(1, test());
+
=======================================
--- /branches/bleeding_edge/src/hydrogen.cc Tue Dec 7 03:53:19 2010
+++ /branches/bleeding_edge/src/hydrogen.cc Tue Dec 7 04:07:40 2010
@@ -3977,17 +3977,27 @@
if (body->HasExit()) {
// Add a return of undefined if control can fall off the body. In a
// test context, undefined is false.
- HValue* return_value = NULL;
- HBasicBlock* target = NULL;
+ HValue* return_value = graph()->GetConstantUndefined();
if (test_context == NULL) {
ASSERT(function_return_ != NULL);
- return_value = graph()->GetConstantUndefined();
- target = function_return_;
+ body->exit_block()->AddLeaveInlined(return_value, function_return_);
} else {
- return_value = graph()->GetConstantFalse();
- target = test_context->if_false();
- }
- body->exit_block()->AddLeaveInlined(return_value, target);
+ // The graph builder assumes control can reach both branches of a
+ // test, so we materialize the undefined value and test it rather
than
+ // simply jumping to the false target.
+ //
+ // TODO(3168478): refactor to avoid this.
+ HBasicBlock* materialize_true = graph()->CreateBasicBlock();
+ HBasicBlock* materialize_false = graph()->CreateBasicBlock();
+ HBranch* branch =
+ new HBranch(materialize_true, materialize_false, return_value);
+ body->exit_block()->Finish(branch);
+
+ materialize_true->AddLeaveInlined(graph()->GetConstantTrue(),
+ test_context->if_true());
+ materialize_false->AddLeaveInlined(graph()->GetConstantFalse(),
+ test_context->if_false());
+ }
body->set_exit_block(NULL);
}
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