[PATCH] D16837: Disable the vzeroupper insertion pass on PS4
Paul Robinson via llvm-commits
llvm-commits at lists.llvm.org
Wed Feb 3 07:19:06 PST 2016
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probinson added a comment.
As long as the consequence of running such code on a non-btver2 CPU is merely performance, not correctness.
I seem to remember that being a concern in the first attempt at turning off vzeroupper, years ago. Something about the consistency of behavior of code in a library, IIRC, when caller and callee were compiled for different CPUs and did not have the same concept of whether the upper parts had been zeroed. Sorry I don't remember the specifics better than that, and I certainly don't know enough about the microarchitectural details to say one way or the other.
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