[PATCH] D69334: [MathExtras] Add intrinsic for the PopulationCounter in Visual Studio

Mon Oct 28 23:35:27 PDT 2019

ekatz added a comment.

In D69334#1724435 <https://reviews.llvm.org/D69334#1724435>, @craig.topper wrote:

> Never does what optimization?

Sorry, I though you meant that MSVC will automatically convert the //popcnt bit twiddling pattern// to the `popcnt` intrinsic. This optimization is done in LLVM, but not in MSVC.

In any case, as I wrote:

In D69334#1724314 <https://reviews.llvm.org/D69334#1724314>, @ekatz wrote:

> Regarding the supported CPU issue; Nehalem is over a decade old. How far back do we want to support? I think it is reasonable to assume `popcnt` is always available.

Repository:
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https://reviews.llvm.org/D69334