[all-commits] [llvm/llvm-project] 833d4d: [profile] Make {__start_, __stop_}__llvm_prf_* symb...

[Fangrui Song via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 833d4d8e89e93636e904c3aa52a6c9c8d2ca098f
      https://github.com/llvm/llvm-project/commit/833d4d8e89e93636e904c3aa52a6c9c8d2ca098f
  Author: Fangrui Song <i at maskray.me>
  Date:   2021-02-17 (Wed, 17 Feb 2021)

  Changed paths:
    M compiler-rt/lib/profile/InstrProfilingPlatformLinux.c

  Log Message:
  -----------
  [profile] Make {__start_,__stop_}__llvm_prf_* symbols undefined weak

To make a kind of metadata section usage work, we want to drop the
`__start_/__stop_ references retain C identifier name sections` rule from LLD (see D96914).

If an application has no `__llvm_prf_data` input section surviving --gc-sections,
LLD will error for undefined hidden `{__start_,__stop_}__llvm_prf_*` from `libclang_rt.profile-*`.
Other `__llvm_prf_*` sections have similar issues.

Making the references weak can address the problem.
This probably enables the opportunity to drop zero size dummy sections in `InstrProfilingPlatformLinux.c`.

Reviewed By: davidxl

Differential Revision: https://reviews.llvm.org/D96936