[all-commits] [llvm/llvm-project] 22f127: [ThinLTO][ELF] Add --thinlto-emit-index-files option

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  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 22f1273357cfe1d7d6e395c447d1be10360cffaa
      https://github.com/llvm/llvm-project/commit/22f1273357cfe1d7d6e395c447d1be10360cffaa
  Author: Jin Xin Ng <njx at google.com>
  Date:   2022-06-23 (Thu, 23 Jun 2022)

  Changed paths:
    M lld/ELF/Config.h
    M lld/ELF/Driver.cpp
    M lld/ELF/LTO.cpp
    M lld/ELF/Options.td
    A lld/test/ELF/lto/thinlto-emit-index.ll
    M llvm/include/llvm/LTO/LTO.h
    M llvm/lib/LTO/LTO.cpp

  Log Message:
  -----------
  [ThinLTO][ELF] Add --thinlto-emit-index-files option

Allows ThinLTO indices to be written to disk on-the-fly/as-part-of “normal” linker execution. Previously ThinLTO indices could be written via --thinlto-index-only but that would cause the linker to exit early. For MLGO specifically, this enables saving the ThinLTO index files without having to restart the linker to collect data only available at later stages (i.e. output of --save-temps) of the linker's execution.

Note, this option does not currently work with:
--thinlto-object-suffix-replace, as this is intended to be used to consume minimized IR bitcode files while --thinlto-emit-index-files is intended to be run together with InProcessThinLTO (which cannot parse minimized IR).
--thinlto-prefix-replace  support is left unimplemented but can be implemented if needed

Differential Revision: https://reviews.llvm.org/D127777