Reviewers: Erik Corry,
Description:
Use SSE2 registers when comparing identical heap numbers on X64.
Please review this at http://codereview.chromium.org/2850018/show
SVN Base: http://v8.googlecode.com/svn/branches/bleeding_edge/
Affected files:
M src/x64/codegen-x64.cc
Index: src/x64/codegen-x64.cc
===================================================================
--- src/x64/codegen-x64.cc (revision 4906)
+++ src/x64/codegen-x64.cc (working copy)
@@ -8966,33 +8966,20 @@
__ ret(0);
__ bind(&heap_number);
- // It is a heap number, so return non-equal if it's NaN and equal if
- // it's not NaN.
- // The representation of NaN values has all exponent bits (52..62)
set,
- // and not all mantissa bits (0..51) clear.
- // We only allow QNaNs, which have bit 51 set (which also rules out
- // the value being Infinity).
+ // It is a heap number, so return equal if it's not NaN.
+ // For NaN, return 1 for every condition except greater and
+ // greater-equal. Return -1 for them, so the comparison yields
+ // false for all conditions except not-equal.
- // Value is a QNaN if value & kQuietNaNMask == kQuietNaNMask, i.e.,
- // all bits in the mask are set. We only need to check the word
- // that contains the exponent and high bit of the mantissa.
- ASSERT_NE(0, (kQuietNaNHighBitsMask << 1) & 0x80000000u);
- __ movl(rdx, FieldOperand(rdx, HeapNumber::kExponentOffset));
- __ xorl(rax, rax);
- __ addl(rdx, rdx); // Shift value and mask so mask applies to top
bits.
- __ cmpl(rdx, Immediate(kQuietNaNHighBitsMask << 1));
- if (cc_ == equal) {
- __ setcc(above_equal, rax);
- __ ret(0);
- } else {
- Label nan;
- __ j(above_equal, &nan);
- __ Set(rax, EQUAL);
- __ ret(0);
- __ bind(&nan);
- __ Set(rax, NegativeComparisonResult(cc_));
- __ ret(0);
+ __ movsd(xmm0, FieldOperand(rdx, HeapNumber::kValueOffset));
+ __ xorl(rax, rax); // Clear rax because setcc only modifies al.
+ __ ucomisd(xmm0, xmm0);
+ __ setcc(parity_even, rax);
+ // rax is 0 for equal non-NaN heapnumbers, 1 for NaNs.
+ if (cc_ == greater_equal || cc_ == greater) {
+ __ neg(rax);
}
+ __ ret(0);
}
__ bind(¬_identical);
--
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