[all-commits] [llvm/llvm-project] f50aef: Revert "[InstrProfiling] Don't generate __llvm_pro...

[Hans via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: f50aef745c3ba981f3d0bf118b809d0c3880a490
      https://github.com/llvm/llvm-project/commit/f50aef745c3ba981f3d0bf118b809d0c3880a490
  Author: Hans Wennborg <hans at chromium.org>
  Date:   2021-03-12 (Fri, 12 Mar 2021)

  Changed paths:
    M clang/docs/UsersManual.rst
    M clang/lib/Driver/ToolChains/Fuchsia.cpp
    M clang/lib/Driver/ToolChains/Fuchsia.h
    M clang/lib/Driver/ToolChains/Linux.cpp
    M clang/lib/Driver/ToolChains/Linux.h
    M clang/test/Driver/coverage-ld.c
    M clang/test/Driver/fuchsia.c
    M llvm/include/llvm/ProfileData/InstrProf.h
    M llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
    M llvm/test/Instrumentation/InstrProfiling/linkage.ll
    M llvm/test/Instrumentation/InstrProfiling/profiling.ll

  Log Message:
  -----------
  Revert "[InstrProfiling] Don't generate __llvm_profile_runtime_user"

This broke the check-profile tests on Mac, see comment on the code
review.

> This is no longer needed, we can add __llvm_profile_runtime directly
> to llvm.compiler.used or llvm.used to achieve the same effect.
>
> Differential Revision: https://reviews.llvm.org/D98325

This reverts commit c7712087cbb505d324e1149fa224f607c91a8c6a.

Also reverting the dependent follow-up commit:

Revert "[InstrProfiling] Generate runtime hook for ELF platforms"

> When using -fprofile-list to selectively apply instrumentation only
> to certain files or functions, we may end up with a binary that doesn't
> have any counters in the case where no files were selected. However,
> because on Linux and Fuchsia, we pass -u__llvm_profile_runtime, the
> runtime would still be pulled in and incur some non-trivial overhead,
> especially in the case when the continuous or runtime counter relocation
> mode is being used. A better way would be to pull in the profile runtime
> only when needed by declaring the __llvm_profile_runtime symbol in the
> translation unit only when needed.
>
> This approach was already used prior to 9a041a75221ca, but we changed it
> to always generate the __llvm_profile_runtime due to a TAPI limitation.
> Since TAPI is only used on Mach-O platforms, we could use the early
> emission of __llvm_profile_runtime there, and on other platforms we
> could change back to the earlier approach where the symbol is generated
> later only when needed. We can stop passing -u__llvm_profile_runtime to
> the linker on Linux and Fuchsia since the generated undefined symbol in
> each translation unit that needed it serves the same purpose.
>
> Differential Revision: https://reviews.llvm.org/D98061

This reverts commit 87fd09b25f8892e07b7ba11525baa9c3ec3e5d3f.