[PATCH] D36454: [X86] Changes to extract Horizontal addition operation for AVX-512.

[Craig Topper via Phabricator via llvm-commits]

craig.topper added a comment.

Thinking about this some more. Do we really want to use a horizontal add instruction for a register with itself? Horizontal add is suboptimally implemented in microcode. It's 3 uops while the pshufd and the add are only 2 uops. The 3 uops also mean its limited to the complex decoder on Intel hardware.


https://reviews.llvm.org/D36454