[all-commits] [llvm/llvm-project] 2638aa: [LLD][ThinLTO] Add --thinlto-single-module to allo...

[Hongtao Yu via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 2638aafe1203f64983017f8998fb09ce986a1b28
      https://github.com/llvm/llvm-project/commit/2638aafe1203f64983017f8998fb09ce986a1b28
  Author: Hongtao Yu <hoy at fb.com>
  Date:   2020-06-10 (Wed, 10 Jun 2020)

  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-single-module.ll
    M llvm/include/llvm/LTO/Config.h
    M llvm/include/llvm/LTO/LTO.h
    M llvm/lib/LTO/LTO.cpp

  Log Message:
  -----------
  [LLD][ThinLTO] Add --thinlto-single-module to allow compiling partial modules.

This change introduces an LLD switch --thinlto-single-module to allow compiling only a part of the input modules. This is specifically enables:

  1. Fast investigating/debugging modules of interest without spending time on compiling unrelated modules.
  2. Compiler debug dump with -mllvm -debug-only= for specific modules.

It will be useful for large applications which has 1K+ input modules for thinLTO.

The switch can be combined with `--lto-obj-path=` or `--lto-emit-asm` to obtain intermediate object files or assembly files. So far the module name matching is implemented as a fuzzy name lookup where the modules with name containing the switch value are compiled.

E.g,
Command:
     ld.lld main.o thin.a --thinlto-single-module=thin.a --lto-obj-path=single.o
log:
     [ThinLTO] Selecting thin.a(thin1.o at 168) to compile
     [ThinLTO] Selecting thin.a(thin2.o at 228) to compile
Command:
     ld.lld main.o thin.a --thinlto-single-module=thin1.o --lto-obj-path=single.o
log:
     [ThinLTO] Selecting thin.a(thin1.o at 168) to compile

Differential Revision: https://reviews.llvm.org/D80406