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Fix bug in the count operation where we statically know the input is a smi.

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Even if we know that the input to a count operation is a smi we still need to check if the result overflowed (and becomes a heap number).

Also fix the smi loop analysis to take two border cases correctly into account.

Review URL: http://codereview.chromium.org/1040002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4147 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
fschneider@chromium.org 2010-03-16 16:03:40 +00:00
parent 78f19f1ae9
commit 9202e05016
3 changed files with 95 additions and 29 deletions
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6
src/data-flow.cc
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@ -1117,6 +1117,12 @@ Variable* AssignedVariablesAnalyzer::FindSmiLoopVariable(ForStatement* stmt) {
if (init_value < term_value && update->op() != Token::INC) return NULL;
if (init_value > term_value && update->op() != Token::DEC) return NULL;
// Check that the update operation cannot overflow the smi range. This can
// occur in the two cases where the loop bound is equal to the largest or
// smallest smi.
if (update->op() == Token::INC && term_value == Smi::kMaxValue) return NULL;
if (update->op() == Token::DEC && term_value == Smi::kMinValue) return NULL;
// Found a smi loop variable.
return loop_var;
}

63
src/ia32/codegen-ia32.cc
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@ -6684,48 +6684,52 @@ void CodeGenerator::VisitCountOperation(CountOperation* node) {
// Ensure the new value is writable.
frame_->Spill(new_value.reg());
// In order to combine the overflow and the smi tag check, we need
// to be able to allocate a byte register. We attempt to do so
// without spilling. If we fail, we will generate separate overflow
// and smi tag checks.
//
// We allocate and clear the temporary byte register before
// performing the count operation since clearing the register using
// xor will clear the overflow flag.
Result tmp = allocator_->AllocateByteRegisterWithoutSpilling();
if (tmp.is_valid()) {
__ Set(tmp.reg(), Immediate(0));
Result tmp;
if (new_value.is_smi()) {
if (FLAG_debug_code) {
__ AbortIfNotSmi(new_value.reg(), "Operand not a smi");
}
} else {
// We don't know statically if the input is a smi.
// In order to combine the overflow and the smi tag check, we need
// to be able to allocate a byte register. We attempt to do so
// without spilling. If we fail, we will generate separate overflow
// and smi tag checks.
// We allocate and clear a temporary byte register before performing
// the count operation since clearing the register using xor will clear
// the overflow flag.
tmp = allocator_->AllocateByteRegisterWithoutSpilling();
if (tmp.is_valid()) {
__ Set(tmp.reg(), Immediate(0));
}
}
if (is_increment) {
__ add(Operand(new_value.reg()), Immediate(Smi::FromInt(1)));
} else {
__ sub(Operand(new_value.reg()), Immediate(Smi::FromInt(1)));
}
if (new_value.is_smi()) {
if (FLAG_debug_code) {
__ AbortIfNotSmi(new_value.reg(), "Argument not a smi");
}
if (tmp.is_valid()) tmp.Unuse();
DeferredCode* deferred = NULL;
if (is_postfix) {
deferred = new DeferredPostfixCountOperation(new_value.reg(),
old_value.reg(),
is_increment);
} else {
DeferredCode* deferred = NULL;
if (is_postfix) {
deferred = new DeferredPostfixCountOperation(new_value.reg(),
old_value.reg(),
is_increment);
} else {
deferred = new DeferredPrefixCountOperation(new_value.reg(),
is_increment);
}
deferred = new DeferredPrefixCountOperation(new_value.reg(),
is_increment);
}
if (new_value.is_smi()) {
// In case we have a smi as input just check for overflow.
deferred->Branch(overflow);
} else {
// If the count operation didn't overflow and the result is a valid
// smi, we're done. Otherwise, we jump to the deferred slow-case
// code.
// We combine the overflow and the smi tag check if we could
// successfully allocate a temporary byte register.
if (tmp.is_valid()) {
// We combine the overflow and the smi tag check if we could
// successfully allocate a temporary byte register.
__ setcc(overflow, tmp.reg());
__ or_(Operand(tmp.reg()), new_value.reg());
__ test(tmp.reg(), Immediate(kSmiTagMask));
@ -6737,8 +6741,9 @@ void CodeGenerator::VisitCountOperation(CountOperation* node) {
__ test(new_value.reg(), Immediate(kSmiTagMask));
deferred->Branch(not_zero);
}
deferred->BindExit();
}
deferred->BindExit();
// Postfix: store the old value in the allocated slot under the
// reference.

55
test/mjsunit/compiler/loopcount.js Normal file
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@ -0,0 +1,55 @@
// 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.
// Test postfix count operations with smis.
function f1() { var x = 0x3fffffff; x++; return x; }
assertEquals(0x40000000, f1());
function f2() { var x = -0x40000000; x--; return x; }
assertEquals(-0x40000001, f2());
function f3(x) { x = x & 0x3fffffff; x++; return x; }
assertEquals(0x40000000, f3(0x3fffffff));
function f4() {
var i;
for (i = 0x3ffffffe; i <= 0x3fffffff; i++) {}
return i;
}
assertEquals(0x40000000, f4());
function f5() {
var i;
for (i = -0x3fffffff; i >= -0x40000000; i--) {}
return i;
}
assertEquals(-0x40000001, f5());