Author: Petr Hosek Date: 2021-09-02T14:15:28-07:00 New Revision: 7a4a5d413624bd8bd54c79e2519ebd80a9ef9acb
URL: https://github.com/llvm/llvm-project/commit/7a4a5d413624bd8bd54c79e2519ebd80a9ef9acb DIFF: https://github.com/llvm/llvm-project/commit/7a4a5d413624bd8bd54c79e2519ebd80a9ef9acb.diff LOG: [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 Added: Modified: llvm/lib/Linker/LinkModules.cpp llvm/test/Linker/comdat4.ll Removed: ################################################################################ diff --git a/llvm/lib/Linker/LinkModules.cpp b/llvm/lib/Linker/LinkModules.cpp index 97d6f8cd80755..efdbc49cdf47c 100644 --- a/llvm/lib/Linker/LinkModules.cpp +++ b/llvm/lib/Linker/LinkModules.cpp @@ -177,9 +177,25 @@ bool ModuleLinker::computeResultingSelectionKind(StringRef ComdatName, // Go with Dst. LinkFromSrc = false; break; - case Comdat::SelectionKind::NoDeduplicate: - return emitError("Linking COMDATs named '" + ComdatName + - "': nodeduplicate has been violated!"); + case Comdat::SelectionKind::NoDeduplicate: { + const GlobalVariable *DstGV; + const GlobalVariable *SrcGV; + if (getComdatLeader(DstM, ComdatName, DstGV) || + getComdatLeader(*SrcM, ComdatName, SrcGV)) + return true; + + if (SrcGV->isWeakForLinker()) { + // Go with Dst. + LinkFromSrc = false; + } else if (DstGV->isWeakForLinker()) { + // Go with Src. + LinkFromSrc = true; + } else { + return emitError("Linking COMDATs named '" + ComdatName + + "': nodeduplicate has been violated!"); + } + break; + } case Comdat::SelectionKind::ExactMatch: case Comdat::SelectionKind::Largest: case Comdat::SelectionKind::SameSize: { diff --git a/llvm/test/Linker/comdat4.ll b/llvm/test/Linker/comdat4.ll index c0af43a516b51..69e1d6efe751c 100644 --- a/llvm/test/Linker/comdat4.ll +++ b/llvm/test/Linker/comdat4.ll @@ -1,5 +1,14 @@ -; RUN: not llvm-link %s %p/Inputs/comdat3.ll -S -o - 2>&1 | FileCheck %s +; RUN: split-file %s %t.dir +; RUN: not llvm-link %t.dir/global.ll %t.dir/global.ll -S -o - 2>&1 | FileCheck %s +; RUN: llvm-link %t.dir/global.ll %t.dir/weak.ll -S -o - 2>&1 +; RUN: llvm-link %t.dir/weak.ll %t.dir/global.ll -S -o - 2>&1 +; RUN: llvm-link %t.dir/weak.ll %t.dir/weak.ll -S -o - 2>&1 +;--- global.ll $foo = comdat nodeduplicate @foo = global i64 43, comdat($foo) ; CHECK: Linking COMDATs named 'foo': nodeduplicate has been violated! + +;--- weak.ll +$foo = comdat nodeduplicate +@foo = weak global i64 43, comdat($foo) _______________________________________________ llvm-branch-commits mailing list llvm-branch-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
