[all-commits] [llvm/llvm-project] 92f54e: [Linker] Support weak symbols in nodeduplicate COM...

[Petr Hosek via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 92f54e1c752253b5a17eb9ec7942f580d878f64d
      https://github.com/llvm/llvm-project/commit/92f54e1c752253b5a17eb9ec7942f580d878f64d
  Author: Petr Hosek <phosek at google.com>
  Date:   2021-08-31 (Tue, 31 Aug 2021)

  Changed paths:
    M llvm/lib/Linker/LinkModules.cpp
    M llvm/test/Linker/comdat-nodeduplicate.ll

  Log Message:
  -----------
  [Linker] Support weak symbols in nodeduplicate COMDAT group

When a nodeduplicate COMDAT group contains a weak symbol, choose
a non-weak symbol (or one of the weak ones) rather than reporting
an error. This should address issue PR51394.

With the current IR representation, a generic comdat nodeduplicate
semantics is not representable for LTO. In the linker, sections and
symbols are separate concepts. A dropped weak symbol does not force the
defining input section to be dropped as well (though it can be collected
by GC). In the IR, when a weak linkage symbol is dropped, its associate
section content is dropped as well.

For InstrProfiling, which is where ran into this issue in PR51394, the
deduplication semantic is a sufficient workaround.

Differential Revision: https://reviews.llvm.org/D108689