From f23847604b2db5a88f0b0b88a2380407b3e7d03f Mon Sep 17 00:00:00 2001 From: Mehdi Amini Date: Sun, 27 Aug 2017 20:24:09 +0000 Subject: Emit static constexpr member as available_externally definition By exposing the constant initializer, the optimizer can fold many of these constructs. Differential Revision: https://reviews.llvm.org/D34992 llvm-svn: 311857 --- clang/lib/CodeGen/CodeGenModule.cpp | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) (limited to 'clang/lib/CodeGen/CodeGenModule.cpp') diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp index c726d90f2e3..5feb6b4d768 100644 --- a/clang/lib/CodeGen/CodeGenModule.cpp +++ b/clang/lib/CodeGen/CodeGenModule.cpp @@ -2437,6 +2437,28 @@ CodeGenModule::GetOrCreateLLVMGlobal(StringRef MangledName, D->getType().isConstant(Context) && isExternallyVisible(D->getLinkageAndVisibility().getLinkage())) GV->setSection(".cp.rodata"); + + // Check if we a have a const declaration with an initializer, we may be + // able to emit it as available_externally to expose it's value to the + // optimizer. + if (Context.getLangOpts().CPlusPlus && GV->hasExternalLinkage() && + D->getType().isConstQualified() && !GV->hasInitializer() && + !D->hasDefinition() && D->hasInit() && !D->hasAttr()) { + const auto *Record = + Context.getBaseElementType(D->getType())->getAsCXXRecordDecl(); + bool HasMutableFields = Record && Record->hasMutableFields(); + if (!HasMutableFields) { + const VarDecl *InitDecl; + const Expr *InitExpr = D->getAnyInitializer(InitDecl); + if (InitExpr) { + GV->setConstant(true); + GV->setLinkage(llvm::GlobalValue::AvailableExternallyLinkage); + ConstantEmitter emitter(*this); + GV->setInitializer(emitter.tryEmitForInitializer(*InitDecl)); + emitter.finalize(GV); + } + } + } } auto ExpectedAS = -- cgit v1.2.3