Revision: 6035
Author: [email protected]
Date: Wed Dec 15 08:14:29 2010
Log: Fix issue 974.
When entering a finally block in unoptimized code, we unconditionally
save the accumulator register in the stack in case it holds a return
value or an exception. In the case of a break, continue, or falling
off the end of the try or catch block, this value is unpredictable and
not necessarily safe for GC.
Review URL: http://codereview.chromium.org/5883003
http://code.google.com/p/v8/source/detail?r=6035
Added:
/branches/bleeding_edge/test/mjsunit/regress/regress-974.js
Modified:
/branches/bleeding_edge/src/arm/full-codegen-arm.cc
/branches/bleeding_edge/src/full-codegen.cc
/branches/bleeding_edge/src/full-codegen.h
/branches/bleeding_edge/src/ia32/full-codegen-ia32.cc
/branches/bleeding_edge/src/x64/full-codegen-x64.cc
=======================================
--- /dev/null
+++ /branches/bleeding_edge/test/mjsunit/regress/regress-974.js Wed Dec 15
08:14:29 2010
@@ -0,0 +1,32 @@
+// 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.
+
+// Flags: --expose-gc
+
+// Verify that GC is safe in a finally block entered by falling off the try
+// block.
+eval("(function(){try { } catch(x) { } finally { gc() }})")();
=======================================
--- /branches/bleeding_edge/src/arm/full-codegen-arm.cc Tue Dec 14 01:47:28
2010
+++ /branches/bleeding_edge/src/arm/full-codegen-arm.cc Wed Dec 15 08:14:29
2010
@@ -204,6 +204,11 @@
// of the stack check table.
masm()->CheckConstPool(true, false);
}
+
+
+void FullCodeGenerator::ClearAccumulator() {
+ __ mov(r0, Operand(Smi::FromInt(0)));
+}
void FullCodeGenerator::EmitStackCheck(IterationStatement* stmt) {
=======================================
--- /branches/bleeding_edge/src/full-codegen.cc Tue Dec 7 03:31:57 2010
+++ /branches/bleeding_edge/src/full-codegen.cc Wed Dec 15 08:14:29 2010
@@ -946,6 +946,11 @@
SetStatementPosition(stmt);
NestedStatement* current = nesting_stack_;
int stack_depth = 0;
+ // When continuing, we clobber the unpredictable value in the accumulator
+ // with one that's safe for GC. If we hit an exit from the try block of
+ // try...finally on our way out, we will unconditionally preserve the
+ // accumulator on the stack.
+ ClearAccumulator();
while (!current->IsContinueTarget(stmt->target())) {
stack_depth = current->Exit(stack_depth);
current = current->outer();
@@ -962,6 +967,11 @@
SetStatementPosition(stmt);
NestedStatement* current = nesting_stack_;
int stack_depth = 0;
+ // When breaking, we clobber the unpredictable value in the accumulator
+ // with one that's safe for GC. If we hit an exit from the try block of
+ // try...finally on our way out, we will unconditionally preserve the
+ // accumulator on the stack.
+ ClearAccumulator();
while (!current->IsBreakTarget(stmt->target())) {
stack_depth = current->Exit(stack_depth);
current = current->outer();
@@ -1235,7 +1245,10 @@
Visit(stmt->try_block());
__ PopTryHandler();
}
- // Execute the finally block on the way out.
+ // Execute the finally block on the way out. Clobber the unpredictable
+ // value in the accumulator with one that's safe for GC. The finally
+ // block will unconditionally preserve the accumulator on the stack.
+ ClearAccumulator();
__ Call(&finally_entry);
}
=======================================
--- /branches/bleeding_edge/src/full-codegen.h Wed Dec 15 05:56:41 2010
+++ /branches/bleeding_edge/src/full-codegen.h Wed Dec 15 08:14:29 2010
@@ -286,6 +286,10 @@
static const InlineFunctionGenerator kInlineFunctionGenerators[];
+ // A platform-specific utility to overwrite the accumulator register
+ // with a GC-safe value.
+ void ClearAccumulator();
+
// Compute the frame pointer relative offset for a given local or
// parameter slot.
int SlotOffset(Slot* slot);
=======================================
--- /branches/bleeding_edge/src/ia32/full-codegen-ia32.cc Wed Dec 15
05:56:41 2010
+++ /branches/bleeding_edge/src/ia32/full-codegen-ia32.cc Wed Dec 15
08:14:29 2010
@@ -249,6 +249,11 @@
EmitReturnSequence();
}
}
+
+
+void FullCodeGenerator::ClearAccumulator() {
+ __ Set(eax, Immediate(Smi::FromInt(0)));
+}
void FullCodeGenerator::EmitStackCheck(IterationStatement* stmt) {
=======================================
--- /branches/bleeding_edge/src/x64/full-codegen-x64.cc Tue Dec 14 01:47:28
2010
+++ /branches/bleeding_edge/src/x64/full-codegen-x64.cc Wed Dec 15 08:14:29
2010
@@ -196,6 +196,11 @@
EmitReturnSequence();
}
}
+
+
+void FullCodeGenerator::ClearAccumulator() {
+ __ xor(rax, rax);
+}
void FullCodeGenerator::EmitStackCheck(IterationStatement* stmt) {
--
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