[all-commits] [llvm/llvm-project] 39917b: [lld-macho] Don't sort map file entries by name

[Jez Ng via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 39917b5e0174e0e4206df31da0e32b984c96c404
      https://github.com/llvm/llvm-project/commit/39917b5e0174e0e4206df31da0e32b984c96c404
  Author: Jez Ng <jezng at fb.com>
  Date:   2022-10-25 (Tue, 25 Oct 2022)

  Changed paths:
    M lld/MachO/MapFile.cpp
    M lld/test/MachO/dead-strip.s

  Log Message:
  -----------
  [lld-macho] Don't sort map file entries by name

ld64 emits them in address order but not in alphabetical order. This
sorting is particularly expensive for dead-stripped symbols (which don't
need to be sorted at all, unlike live symbols that need to be sorted by
address).

Timings for chromium_framework_less_dwarf (with the `-map` flag added to
the response file) on my 16-core Mac Pro:

             base           diff           difference (95% CI)
  sys_time   1.997 ± 0.038  2.004 ± 0.028  [  -0.6% ..   +1.3%]
  user_time  8.698 ± 0.085  8.167 ± 0.070  [  -6.6% ..   -5.6%]
  wall_time  7.965 ± 0.114  7.715 ± 0.347  [  -5.1% ..   -1.2%]
  samples    25             23

Reviewed By: #lld-macho, thakis

Differential Revision: https://reviews.llvm.org/D136536