[PATCH] D42981: [COST] Fix cost model of load instructions on X86

[Sanjay Patel via Phabricator via llvm-commits]

spatel added a comment.

The patch is doing what I hoped for on PR36280, but I don't understand the reasoning.

A folded load is not actually free on any x86 CPU AFAIK. It always has an extra uop, and that uop is handled on a different port / execution unit than the math op. The cost model that we're using here is based on throughput rates (let me know if I'm wrong), so I don't see how any load could be free.


Repository:
  rL LLVM

https://reviews.llvm.org/D42981