[PATCH] D131247: [WIP][ELF] Parallelize writes of different OutputSections

[Fangrui Song via Phabricator via llvm-commits]

MaskRay created this revision.
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We currently process one OutputSection at a time and for each OutputSection
write contained input sections in parallel. This strategy does not leverage
threads well. Instead, parallelize writes of different OutputSections.

- Move llvm::parallel::detail::TaskGroup to llvm::parallel::TaskGroup
- Add llvm::asyncParallelFor. We also make TaskSize a paramemter. The default often leads to inferior sharding.
- Change writeSections to declare TaskGroup and pass it to writeTo.

Linking clang and chrome is 1.15x as fast.

WIP as some tests need investigation:

  Failed Tests (5):
    lld :: ELF/arm-thumb-interwork-notfunc.s
    lld :: ELF/common-archive-lookup.s
    lld :: ELF/hexagon-jump-error.s
    lld :: ELF/linkerscript/overlapping-sections.s
    lld :: ELF/ppc64-toc-relax-ifunc.s


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D131247

Files:
  lld/ELF/OutputSections.cpp
  lld/ELF/OutputSections.h
  lld/ELF/Writer.cpp
  lld/test/ELF/arm-thumb-interwork-notfunc.s
  lld/test/ELF/hexagon-jump-error.s
  llvm/include/llvm/Support/Parallel.h
  llvm/lib/Support/Parallel.cpp

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