[PATCH] D55427: [libcxx] Call __count_bool_true for bitset count
Marshall Clow via Phabricator
reviews at reviews.llvm.org
Thu Dec 13 07:38:57 PST 2018
mclow.lists added a comment.
In D55427#1325285 <https://reviews.llvm.org/D55427#1325285>, @zatrazz wrote:
> This patch aims to help clang with better information so it can inline
> __bit_reference count function usage for both std::biset. Current clang
> inliner can not infer that the passed typed will be used only to select
> the optimized variant, it evaluates the type argument and type check as
> a load plus compare (although later optimization phases correctly
> optimized this out).
I'm unclear on the magnitude of the improvement here.
Are we talking a single load + compare instruction in the call to `std::count` ?
Or something inside the loop?
[ I'm pretty sure that the patch is correct now - but I don't understand how important it is ]
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