AuroraMiddleware/v8
1
0
Fork 0
Code Issues 2 Pull Requests Releases Wiki Activity

X64: Added missing optimization of unary negate.

Browse Source 
Review URL: http://codereview.chromium.org/174214


git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2808 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
lrn@chromium.org 2009-09-02 07:49:53 +00:00
parent 23e84069c8
commit de33b1d03d
1 changed files with 35 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

40
src/x64/codegen-x64.cc
View File

@ -6386,7 +6386,7 @@ bool CodeGenerator::FoldConstantSmis(Token::Value op, int left, int right) {
if (answer >= Smi::kMinValue && answer <= Smi::kMaxValue) {
// If the product is zero and the non-zero factor is negative,
// the spec requires us to return floating point negative zero.
if (answer != 0 || (left >= 0 && right >= 0)) {
if (answer != 0 || (left + right) >= 0) {
answer_object = Smi::FromInt(static_cast<int>(answer));
}
}
@ -6454,24 +6454,54 @@ bool CodeGenerator::FoldConstantSmis(Token::Value op, int left, int right) {
void UnarySubStub::Generate(MacroAssembler* masm) {
Label slow;
Label done;
Label try_float;
Label special;
// Check whether the value is a smi.
__ testl(rax, Immediate(kSmiTagMask));
// TODO(X64): Add inline code that handles floats, as on ia32 platform.
__ j(not_zero, &slow);
__ j(not_zero, &try_float);
// Enter runtime system if the value of the smi is zero
// to make sure that we switch between 0 and -0.
// Also enter it if the value of the smi is Smi::kMinValue
__ testl(rax, Immediate(0x7FFFFFFE));
__ j(zero, &slow);
__ j(zero, &special);
__ neg(rax);
__ jmp(&done);
__ bind(&special);
// Either zero or -0x4000000, neither of which become a smi when negated.
__ testl(rax, rax);
__ j(not_zero, &slow);
__ Move(rax, Factory::minus_zero_value());
__ jmp(&done);
// Enter runtime system.
__ bind(&slow);
__ pop(rcx); // pop return address
__ push(rax);
__ push(rcx); // push return address
__ InvokeBuiltin(Builtins::UNARY_MINUS, JUMP_FUNCTION);
__ jmp(&done);
// Try floating point case.
__ bind(&try_float);
__ movq(rdx, FieldOperand(rax, HeapObject::kMapOffset));
__ Cmp(rdx, Factory::heap_number_map());
__ j(not_equal, &slow);
// Operand is a float, negate its value by flipping sign bit.
__ movq(rdx, FieldOperand(rax, HeapNumber::kValueOffset));
__ movq(kScratchRegister, Immediate(0x01));
__ shl(kScratchRegister, Immediate(63));
__ xor_(rdx, kScratchRegister); // Flip sign.
// rdx is value to store.
if (overwrite_) {
__ movq(FieldOperand(rax, HeapNumber::kValueOffset), rdx);
} else {
FloatingPointHelper::AllocateHeapNumber(masm, &slow, rbx, rcx);
// rcx: allocated 'empty' number
__ movq(FieldOperand(rcx, HeapNumber::kValueOffset), rdx);
__ movq(rax, rcx);
}
__ bind(&done);
__ StubReturn(1);