For the non-packed variant of this instruction, a MOVSD instruction was
generated to copy only the lower 64 bits of XMM1 to the destination
register. This was done in order to keep the destination register's
upper half intact.
However, when register c and the destination register are the same,
there is no need for this copy. Because the registers match and due to
the way the mask is generated, BLENDVPD will end up taking the upper
half from the destination register, as intended.
Additionally, the MOVAPS to copy Rc into XMM1 can also be skipped.
Before:
66 0F 57 C0 xorpd xmm0,xmm0
F2 41 0F C2 C6 06 cmpnlesd xmm0,xmm14
41 0F 28 CE movaps xmm1,xmm14
66 41 0F 38 15 CA blendvpd xmm1,xmm10,xmm0
F2 44 0F 10 F1 movsd xmm14,xmm1
After:
66 0F 57 C0 xorpd xmm0,xmm0
F2 41 0F C2 C6 06 cmpnlesd xmm0,xmm14
66 45 0F 38 15 F2 blendvpd xmm14,xmm10,xmm0
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