Reviewers: William Hesse,
Description:
X64: Fix bug in DoBranch that miss detecting NaN as falsy.
Please review this at http://codereview.chromium.org/6369005/
SVN Base: https://v8.googlecode.com/svn/branches/bleeding_edge/build-x64
Affected files:
M src/x64/lithium-codegen-x64.cc
Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index
9938ff0fe0c09a5be482ad8d5e12962569e95ab5..842d68542da818890fc66682bc47ba854988462c
100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -990,12 +990,15 @@ void LCodeGen::DoBranch(LBranch* instr) {
// Test for double values. Plus/minus zero are false. NaN is handled
// in the stub.
NearLabel call_stub;
- __ Cmp(FieldOperand(reg, HeapObject::kMapOffset),
- Factory::heap_number_map());
+ __ CompareRoot(FieldOperand(reg, HeapObject::kMapOffset),
+ Heap::kHeapNumberMapRootIndex);
__ j(not_equal, &call_stub);
- __ movq(kScratchRegister, FieldOperand(reg,
HeapNumber::kValueOffset));
- __ shl(kScratchRegister, Immediate(1)); // Shift out the sign bit.
- __ j(zero, false_label); // Zero or negative zero.
+
+ // HeapNumber => false iff +0, -0, or NaN. These three cases set the
+ // zero flag when compared to zero using ucomisd.
+ __ xorpd(xmm0, xmm0);
+ __ ucomisd(xmm0, FieldOperand(reg, HeapNumber::kValueOffset));
+ __ j(zero, false_label);
__ jmp(true_label);
// The conversion stub doesn't cause garbage collections so it's
--
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