Reviewers: William Hesse, Message: Smallish review.
Description: X64: Added missing optimization of unary negate. Please review this at http://codereview.chromium.org/174214 Affected files: M src/x64/codegen-x64.cc Index: src/x64/codegen-x64.cc diff --git a/src/x64/codegen-x64.cc b/src/x64/codegen-x64.cc index 462b9600eed66b337b6f388d051ab98ebbe50974..f271860961a42be68ef471bed3b8d9874bd9e140 100644 --- a/src/x64/codegen-x64.cc +++ b/src/x64/codegen-x64.cc @@ -6217,7 +6217,7 @@ 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)); } } @@ -6285,24 +6285,54 @@ 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); --~--~---------~--~----~------------~-------~--~----~ v8-dev mailing list [email protected] http://groups.google.com/group/v8-dev -~----------~----~----~----~------~----~------~--~---
