[all-commits] [llvm/llvm-project] 7a4a5d: [Linker] Support weak symbols in nodeduplicate COM...

[Petr Hosek via All-commits]

  Branch: refs/heads/release/13.x
  Home:   https://github.com/llvm/llvm-project
  Commit: 7a4a5d413624bd8bd54c79e2519ebd80a9ef9acb
      https://github.com/llvm/llvm-project/commit/7a4a5d413624bd8bd54c79e2519ebd80a9ef9acb
  Author: Petr Hosek <phosek at google.com>
  Date:   2021-09-02 (Thu, 02 Sep 2021)

  Changed paths:
    M llvm/lib/Linker/LinkModules.cpp
    M llvm/test/Linker/comdat4.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