[PATCH] D91579: [ELF] --gc-sections: collect unused .gcc_except_table in section groups and associated text sections

[Fangrui Song via Phabricator via llvm-commits]

MaskRay created this revision.
Herald added subscribers: llvm-commits, arichardson, emaste.
Herald added a reviewer: espindola.
Herald added a project: LLVM.
MaskRay requested review of this revision.

`try ... catch` in an inline function produces `.gcc_except_table.*` with GCC or
newer Clang (since D83655 <https://reviews.llvm.org/D83655>). For --gc-sections, currently we scan `.eh_frame`
pieces and mark liveness of such a `.gcc_except_table.*` and then the associated
`.text.*` (if a member in a section group is retained, the others should be
retained as well).

Essentially all `.text.*` and `.gcc_except_table.*` compiled from inline
functions with `try ... catch` cannot be discarded by the imprecise --gc-sections.

This patch teaches the .eh_frame piece scanning code to only mark
`.gcc_except_table` in a section group, thus allow unused `.text.*` and
`.gcc_except_table.*` to be discarded.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D91579

Files:
  lld/ELF/MarkLive.cpp
  lld/test/ELF/gc-sections-lsda.s

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