Author: rnk Date: Tue May 7 16:06:21 2019 New Revision: 360207 URL: http://llvm.org/viewvc/llvm-project?rev=360207&view=rev Log: [COFF] Use COFF stubs for extern_weak functions
Summary: A COFF stub indirects the reference to a symbol through memory. A .refptr.$sym global variable pointer is created to refer to $sym. Typically mingw uses these for external global variable declarations, but we can use them for weak function declarations as well. Updates the dso_local classification to add a special case for extern_weak symbols on COFF in both clang and LLVM. Fixes PR37598 Reviewers: smeenai, mstorsjo Subscribers: hiraditya, cfe-commits, llvm-commits Tags: #clang, #llvm Differential Revision: https://reviews.llvm.org/D61615 Modified: cfe/trunk/lib/CodeGen/CodeGenModule.cpp cfe/trunk/test/CodeGen/dso-local-executable.c Modified: cfe/trunk/lib/CodeGen/CodeGenModule.cpp URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenModule.cpp?rev=360207&r1=360206&r2=360207&view=diff ============================================================================== --- cfe/trunk/lib/CodeGen/CodeGenModule.cpp (original) +++ cfe/trunk/lib/CodeGen/CodeGenModule.cpp Tue May 7 16:06:21 2019 @@ -763,6 +763,13 @@ static bool shouldAssumeDSOLocal(const C !GV->isThreadLocal()) return false; } + + // On COFF, don't mark 'extern_weak' symbols as DSO local. If these symbols + // remain unresolved in the link, they can be resolved to zero, which is + // outside the current DSO. + if (TT.isOSBinFormatCOFF() && GV->hasExternalWeakLinkage()) + return false; + // Every other GV is local on COFF. // Make an exception for windows OS in the triple: Some firmware builds use // *-win32-macho triples. This (accidentally?) produced windows relocations Modified: cfe/trunk/test/CodeGen/dso-local-executable.c URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/dso-local-executable.c?rev=360207&r1=360206&r2=360207&view=diff ============================================================================== --- cfe/trunk/test/CodeGen/dso-local-executable.c (original) +++ cfe/trunk/test/CodeGen/dso-local-executable.c Tue May 7 16:06:21 2019 @@ -1,6 +1,6 @@ // RUN: %clang_cc1 -triple x86_64-pc-win32 -emit-llvm %s -o - | FileCheck -allow-deprecated-dag-overlap --check-prefix=COFF %s // COFF-DAG: @bar = external dso_local global i32 -// COFF-DAG: @weak_bar = extern_weak dso_local global i32 +// COFF-DAG: @weak_bar = extern_weak global i32 // COFF-DAG: declare dso_local void @foo() // COFF-DAG: @baz = dso_local global i32 42 // COFF-DAG: define dso_local i32* @zed() _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
