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Fix optimized code for Math.round on ia32 platform.

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Review URL: http://codereview.chromium.org/6838012

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7600 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
whesse@chromium.org 2011-04-13 10:32:05 +00:00
parent caee8a3ccf
commit 5a6ec1a46e
1 changed files with 24 additions and 12 deletions
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36
src/ia32/lithium-codegen-ia32.cc
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@ -2707,25 +2707,16 @@ void LCodeGen::DoMathRound(LUnaryMathOperation* instr) {
Register output_reg = ToRegister(instr->result());
XMMRegister input_reg = ToDoubleRegister(instr->InputAt(0));
Label below_half, done;
// xmm_scratch = 0.5
ExternalReference one_half = ExternalReference::address_of_one_half();
__ movdbl(xmm_scratch, Operand::StaticVariable(one_half));
__ ucomisd(xmm_scratch, input_reg);
__ j(above, &below_half);
// input = input + 0.5
__ addsd(input_reg, xmm_scratch);
// We need to return -0 for the input range [-0.5, 0[, otherwise
// compute Math.floor(value + 0.5).
if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
__ ucomisd(input_reg, xmm_scratch);
DeoptimizeIf(below_equal, instr->environment());
} else {
// If we don't need to bailout on -0, we check only bailout
// on negative inputs.
__ xorpd(xmm_scratch, xmm_scratch); // Zero the register.
__ ucomisd(input_reg, xmm_scratch);
DeoptimizeIf(below, instr->environment());
}
// Compute Math.floor(value + 0.5).
// Use truncating instruction (OK because input is positive).
@ -2734,6 +2725,27 @@ void LCodeGen::DoMathRound(LUnaryMathOperation* instr) {
// Overflow is signalled with minint.
__ cmp(output_reg, 0x80000000u);
DeoptimizeIf(equal, instr->environment());
__ jmp(&done);
__ bind(&below_half);
// We return 0 for the input range [+0, 0.5[, or [-0.5, 0.5[ if
// we can ignore the difference between a result of -0 and +0.
if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
// If the sign is positive, we return +0.
__ movmskpd(output_reg, input_reg);
__ test(output_reg, Immediate(1));
DeoptimizeIf(not_zero, instr->environment());
} else {
// If the input is >= -0.5, we return +0.
__ mov(output_reg, Immediate(0xBF000000));
__ movd(xmm_scratch, Operand(output_reg));
__ cvtss2sd(xmm_scratch, xmm_scratch);
__ ucomisd(input_reg, xmm_scratch);
DeoptimizeIf(below, instr->environment());
}
__ Set(output_reg, Immediate(0));
__ bind(&done);
}