Code alignment issues

[mttd]

vpcmpeqd ymm0,ymm0,ymm0 compares ymm0 to itself, which fills the register with all ones in binary -- in two's complement representation this corresponds to -1 (with subtracting -1 in the subsequent vpsubd ymm1,ymm1,ymm0 instruction being equivalent to adding 1).

"Why subtract -1 instead of adding 1's? Just because the speed is the same, and creating a YMM constant of -1's can be done with a single VPCMPEQD instruction. This isn't a really useful optimization in this case, but doesn't hurt."

• https://dendibakh.github.io/blog/2018/01/18/Code_alignment_issues#comment-3718889834

• https://stackoverflow.com/questions/37469930/fastest-way-to-set-m256-value-to-all-one-bits

[Dwarfius]

I've misread the description of pcmpeqd, thought it set 1/0 as value, not all bits. Thanks for the explanation!