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Improve code generated for left shifts where the left side

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is a constant by avoiding a few checks.
Review URL: http://codereview.chromium.org/504057

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3495 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
kasperl@chromium.org 2009-12-18 13:07:02 +00:00
parent 56a6b0cdff
commit 0b4e755047
1 changed files with 36 additions and 3 deletions
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37
src/ia32/codegen-ia32.cc
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@ -1731,9 +1731,42 @@ void CodeGenerator::ConstantSmiBinaryOperation(Token::Value op,
case Token::SHL:
if (reversed) {
Result constant_operand(value);
LikelySmiBinaryOperation(op, &constant_operand, operand,
Result right;
Result right_copy_in_ecx;
// Make sure to get a copy of the right operand into ecx. This
// allows us to modify it without having to restore it in the
// deferred code.
operand->ToRegister();
if (operand->reg().is(ecx)) {
right = allocator()->Allocate();
__ mov(right.reg(), ecx);
frame_->Spill(ecx);
right_copy_in_ecx = *operand;
} else {
right_copy_in_ecx = allocator()->Allocate(ecx);
__ mov(ecx, operand->reg());
right = *operand;
}
operand->Unuse();
Result answer = allocator()->Allocate();
DeferredInlineSmiOperation* deferred =
new DeferredInlineSmiOperation(op,
answer.reg(),
right.reg(),
smi_value,
overwrite_mode);
__ mov(answer.reg(), Immediate(int_value));
__ sar(ecx, kSmiTagSize);
deferred->Branch(carry);
__ shl_cl(answer.reg());
__ cmp(answer.reg(), 0xc0000000);
deferred->Branch(sign);
__ SmiTag(answer.reg());
deferred->BindExit();
frame_->Push(&answer);
} else {
// Only the least significant 5 bits of the shift value are used.
// In the slow case, this masking is done inside the runtime call.