[PATCH] D95960: [llvm][IR] Do not place constants with static relocations in a mergeable section

[Leonard Chan via Phabricator via llvm-commits]

leonardchan created this revision.
leonardchan added reviewers: phosek, mcgrathr, pcc.
leonardchan added a project: LLVM.
Herald added subscribers: dexonsmith, pengfei, hiraditya.
leonardchan requested review of this revision.

This patch provides two major changes:

1. Add `needsStaticRelocation` to check if a constant will have dso_local relocations that can can be resolved by the static linker. (Also rename the original `needsRelocation` to `needsDynamicRelocation`.)
2. Only allow a constant with no relocations (static or dynamic) to be placed in a mergeable section.

This will allow unused symbols that contain static relocations and happen to fit in mergeable constant sections (`.rodata.cstN`) to instead be placed in unique-named sections if `-fdata-sections` is used and subsequently garbage collected by `--gc-sections`.

See https://lists.llvm.org/pipermail/llvm-dev/2021-February/148281.html.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D95960

Files:
  llvm/include/llvm/IR/Constant.h
  llvm/lib/IR/Constants.cpp
  llvm/lib/Target/TargetLoweringObjectFile.cpp
  llvm/test/CodeGen/X86/relptr-rodata.ll

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