From db5e0786900e53843f87c4169c404f8c7831eb8c Mon Sep 17 00:00:00 2001 From: Fangrui Song Date: Tue, 20 Jul 2021 13:22:00 -0700 Subject: [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 --- llvm/lib/Object/IRSymtab.cpp | 1 + 1 file changed, 1 insertion(+) (limited to 'llvm/lib/Object/IRSymtab.cpp') diff --git a/llvm/lib/Object/IRSymtab.cpp b/llvm/lib/Object/IRSymtab.cpp index bcada85..746b008 100644 --- a/llvm/lib/Object/IRSymtab.cpp +++ b/llvm/lib/Object/IRSymtab.cpp @@ -199,6 +199,7 @@ Expected Builder::getComdatIndex(const Comdat *C, const Module *M) { storage::Comdat Comdat; setStr(Comdat.Name, Saver.save(Name)); + Comdat.SelectionKind = C->getSelectionKind(); Comdats.push_back(Comdat); } -- cgit v1.1