[PATCH] D24108: X86: Fold tail calls into conditional branches where possible (PR26302)

Maksim Panchenko via llvm-commits llvm-commits at lists.llvm.org
Thu Sep 1 14:05:09 PDT 2016

maksfb added a comment.

@hans: I think it is safe to do this optimization while optimizing for size. If you do it by default it could be a performance regression if you reverse direction of the conditional branch. That's what we found out while testing on a micro benchmark. I believe it's related to the way BTB works on Intel's CPUs. The problem is that unless you are doing LTO or work at the binary level, you don't always know the new direction of the branch.


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