[all-commits] [llvm/llvm-project] 865ad6: [libc++] Use __libcpp_clz for a tighter __log2i fu...

[Hans via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 865ad6bd21656aef5fabd2f4603ad4f759df6e62
      https://github.com/llvm/llvm-project/commit/865ad6bd21656aef5fabd2f4603ad4f759df6e62
  Author: Hans Wennborg <hans at chromium.org>
  Date:   2022-05-27 (Fri, 27 May 2022)

  Changed paths:
    M libcxx/include/__algorithm/sort.h

  Log Message:
  -----------
  [libc++] Use __libcpp_clz for a tighter __log2i function

While looking at D113413 I noticed that __log2i could perhaps be
improved to be both slightly smaller and faster.

projects/libcxx/benchmarks/sort.libcxx.out --benchmark_filter=BM_Sort_uint32_QuickSortAdversary*
suggests this is performance neutral, but it shaves a few bytes off the
benchmark binary, and even more off a Chromium build.

Differential revision: https://reviews.llvm.org/D125958