Fangrui Song 2174d3b961 [LTO] Add SelectionKind to IRSymtab and use it in ld.lld/LLVMgold ... In PGO, a C++ external linkage function `foo` has a private counter `__profc_foo` and a private `__profd_foo` in a `comdat nodeduplicate`. A `__attribute__((weak))` function `foo` has a weak hidden counter `__profc_foo` and a private `__profd_foo` in a `comdat nodeduplicate`. In `ld.lld a.o b.o`, say a.o defines an external linkage `foo` and b.o defines a weak `foo`. Currently we treat `comdat nodeduplicate` as `comdat any`, ld.lld will incorrectly consider `b.o:__profc_foo` non-prevailing. In the worst case when `b.o:__profd_foo` is retained and `b.o:__profc_foo` isn't, there will be dangling reference causing an `undefined hidden symbol` error. Add SelectionKind to `Comdat` in IRSymtab and let linkers ignore nodeduplicate comdat. Differential Revision: https://reviews.llvm.org/D106228		2021-07-20 13:22:00 -07:00
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CMakeLists.txt
llvm-lto2.cpp