[PATCH] D84766: Revert D68041 "[PGO] Don't group COMDAT variables for compiler generated profile variables in ELF"

[Fangrui Song via Phabricator via llvm-commits]

MaskRay created this revision.
MaskRay added reviewers: davidxl, xur, yamauchi.
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This reverts commit 367405008755640eac6114b18ec8c98be0cf5392, which only affected ELF
platforms.

The state before this patch was inferior because the section group signature
(comdat name in LLVM IR) `__profv_` consumes one entry in .symtab and a
(potentially long) entry in .strtab . The patch avoided the cost but introduced new
issues:

- One or two additional section headers (64 or 128 bytes on ELF64).
- If the prevailing group does not include `__profvp_` (value profiling not used) but a non-prevailing group from another translation unit has `__profvp_` (the function is inlined into another and triggers value profiling), there will be a stray `__profvp_`.

We are currently investigating a mysterious PGO timeout. When things get
stabalized, we can do D84723 <https://reviews.llvm.org/D84723>.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D84766

Files:
  llvm/include/llvm/ProfileData/InstrProf.h
  llvm/lib/Transforms/Instrumentation/InstrProfiling.cpp
  llvm/test/Instrumentation/InstrProfiling/PR23499.ll
  llvm/test/Instrumentation/InstrProfiling/comdat.ll
  llvm/test/Instrumentation/InstrProfiling/linkage.ll
  llvm/test/Transforms/PGOProfile/comdat_internal.ll

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