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Use comdats to avoid double initialization of weak data

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Initializers of global data that can appear multiple TUs (static data
members of class templates or __declspec(selectany) data) are now in a
comdat group keyed on the global variable being initialized.  On
non-Windows platforms, this is a code size and startup time
optimization.  On Windows, this is necessary for ABI compatibility with
MSVC.

Fixes PR16959.

Reviewers: rsmith

Differential Revision: http://reviews.llvm.org/D3811

llvm-svn: 209555
This commit is contained in:
Reid Kleckner
2014-05-23 21:13:45 +00:00
parent 2f75351c02
commit 563f0e852c
8 changed files with 78 additions and 51 deletions
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22
clang/lib/CodeGen/CodeGenModule.cpp
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@@ -511,16 +511,17 @@ llvm::GlobalValue *CodeGenModule::GetGlobalValue(StringRef Name) {
/// AddGlobalCtor - Add a function to the list that will be called before
/// main() runs.
void CodeGenModule::AddGlobalCtor(llvm::Function * Ctor, int Priority) {
void CodeGenModule::AddGlobalCtor(llvm::Function *Ctor, int Priority,
llvm::Constant *AssociatedData) {
// FIXME: Type coercion of void()* types.
GlobalCtors.push_back(std::make_pair(Ctor, Priority));
GlobalCtors.push_back(Structor(Priority, Ctor, AssociatedData));
}
/// AddGlobalDtor - Add a function to the list that will be called
/// when the module is unloaded.
void CodeGenModule::AddGlobalDtor(llvm::Function * Dtor, int Priority) {
void CodeGenModule::AddGlobalDtor(llvm::Function *Dtor, int Priority) {
// FIXME: Type coercion of void()* types.
GlobalDtors.push_back(std::make_pair(Dtor, Priority));
GlobalDtors.push_back(Structor(Priority, Dtor, 0));
}
void CodeGenModule::EmitCtorList(const CtorList &Fns, const char *GlobalName) {
@@ -528,16 +529,19 @@ void CodeGenModule::EmitCtorList(const CtorList &Fns, const char *GlobalName) {
llvm::FunctionType* CtorFTy = llvm::FunctionType::get(VoidTy, false);
llvm::Type *CtorPFTy = llvm::PointerType::getUnqual(CtorFTy);
// Get the type of a ctor entry, { i32, void ()* }.
llvm::StructType *CtorStructTy =
llvm::StructType::get(Int32Ty, llvm::PointerType::getUnqual(CtorFTy), NULL);
// Get the type of a ctor entry, { i32, void ()*, i8* }.
llvm::StructType *CtorStructTy = llvm::StructType::get(
Int32Ty, llvm::PointerType::getUnqual(CtorFTy), VoidPtrTy, NULL);
// Construct the constructor and destructor arrays.
SmallVector<llvm::Constant*, 8> Ctors;
for (CtorList::const_iterator I = Fns.begin(), E = Fns.end(); I != E; ++I) {
llvm::Constant *S[] = {
llvm::ConstantInt::get(Int32Ty, I->second, false),
llvm::ConstantExpr::getBitCast(I->first, CtorPFTy)
llvm::ConstantInt::get(Int32Ty, I->Priority, false),
llvm::ConstantExpr::getBitCast(I->Initializer, CtorPFTy),
(I->AssociatedData
? llvm::ConstantExpr::getBitCast(I->AssociatedData, VoidPtrTy)
: llvm::Constant::getNullValue(VoidPtrTy))
};
Ctors.push_back(llvm::ConstantStruct::get(CtorStructTy, S));
}