[PATCH] D84723: [PGO] Move __profc_ and __profvp_ from their own comdat groups to __profd_'s comdat group

[Fangrui Song via Phabricator via llvm-commits]

MaskRay created this revision.
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`__profc_` and `__profvp_` are referenced by `__profd_`. The 3 symbols can and
should be retained or discarded as a whole. We can use one comdat instead of 2
(value profiling not used) or 3 (value profiling used).

If the prevailing group is a translation unit without `__profvp_`, previously we
may add a stray `__profvp_` from a non-prevailing group. This change fixes this
behavior.

For each function which should be placed in a comdat, this saves at most two
section headers (2*sizeof(Elf64_Shdr) = 128 bytes) on an ELF64 platform.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D84723

Files:
  llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
  llvm/test/Instrumentation/InstrProfiling/PR23499.ll
  llvm/test/Instrumentation/InstrProfiling/comdat.ll
  llvm/test/Instrumentation/InstrProfiling/icall.ll
  llvm/test/Instrumentation/InstrProfiling/linkage.ll
  llvm/test/Transforms/PGOProfile/comdat_internal.ll

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