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This code: float floatingPointComparison(float x, float y) { double product = (double)x * y; if (product == 0.0) return product; return product - 1.0; } produces this: _floatingPointComparison: 0000000000000000 cvtss2sd %xmm1,%xmm1 0000000000000004 cvtss2sd %xmm0,%xmm0 0000000000000008 mulsd %xmm1,%xmm0 000000000000000c pxor %xmm1,%xmm1 0000000000000010 ucomisd %xmm1,%xmm0 0000000000000014 jne 0x00000004 0000000000000016 jp 0x00000002 0000000000000018 jmp 0x00000008 000000000000001a addsd 0x00000006(%rip),%xmm0 0000000000000022 cvtsd2ss %xmm0,%xmm0 0000000000000026 ret The "jne/jp/jmp" sequence can be reduced to this instead: _floatingPointComparison: 0000000000000000 cvtss2sd %xmm1,%xmm1 0000000000000004 cvtss2sd %xmm0,%xmm0 0000000000000008 mulsd %xmm1,%xmm0 000000000000000c pxor %xmm1,%xmm1 0000000000000010 ucomisd %xmm1,%xmm0 0000000000000014 jp 0x00000002 0000000000000016 je 0x00000008 0000000000000018 addsd 0x00000006(%rip),%xmm0 0000000000000020 cvtsd2ss %xmm0,%xmm0 0000000000000024 ret for a savings of 2 bytes. This xform can happen when we recognize that jne and jp jump to the same "true" MBB, the unconditional jump would jump to the "false" MBB, and the "true" branch is the fall-through MBB. llvm-svn: 97766 |
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