From 899ded9cdf53b3d84c8d0e771851cc256296bfd2 Mon Sep 17 00:00:00 2001 From: Hans Wennborg Date: Thu, 16 Oct 2014 20:52:46 +0000 Subject: MS Compat: mark globals emitted in read-only sections const They cannot be written to, so marking them const makes sense and may improve optimisation. As a side-effect, SectionInfos has to be moved from Sema to ASTContext. It also fixes this problem, that occurs when compiling ATL: warning LNK4254: section 'ATL' (C0000040) merged into '.rdata' (40000040) with different attributes The ATL headers are putting variables in a special section that's marked read-only. However, Clang currently can't model that read-onlyness in the IR. But, by making the variables const, the section does become read-only, and the linker warning is avoided. Differential Revision: http://reviews.llvm.org/D5812 llvm-svn: 219960 --- clang/lib/CodeGen/CodeGenModule.cpp | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'clang/lib/CodeGen/CodeGenModule.cpp') diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp index 7d8c34d19960..78a2631a3661 100644 --- a/clang/lib/CodeGen/CodeGenModule.cpp +++ b/clang/lib/CodeGen/CodeGenModule.cpp @@ -1931,6 +1931,13 @@ void CodeGenModule::EmitGlobalVarDefinition(const VarDecl *D) { GV->setConstant(!NeedsGlobalCtor && !NeedsGlobalDtor && isTypeConstant(D->getType(), true)); + // If it is in a read-only section, mark it 'constant'. + if (const SectionAttr *SA = D->getAttr()) { + const ASTContext::SectionInfo &SI = Context.SectionInfos[SA->getName()]; + if ((SI.SectionFlags & ASTContext::PSF_Write) == 0) + GV->setConstant(true); + } + GV->setAlignment(getContext().getDeclAlign(D).getQuantity()); // Set the llvm linkage type as appropriate. -- cgit v1.2.3