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Add comdat key field to llvm.global_ctors and llvm.global_dtors

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This allows us to put dynamic initializers for weak data into the same
comdat group as the data being initialized.  This is necessary for MSVC
ABI compatibility.  Once we have comdats for guard variables, we can use
the combination to help GlobalOpt fire more often for weak data with
guarded initialization on other platforms.

Reviewers: nlewycky

Differential Revision: http://reviews.llvm.org/D3499

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209015 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Reid Kleckner
2014-05-16 20:39:27 +00:00
parent dedd6203ad
commit 1ce3088669
16 changed files with 289 additions and 69 deletions
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29
lib/Transforms/Utils/ModuleUtils.cpp
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@ -24,16 +24,16 @@ static void appendToGlobalArray(const char *Array,
Module &M, Function *F, int Priority) {
IRBuilder<> IRB(M.getContext());
FunctionType *FnTy = FunctionType::get(IRB.getVoidTy(), false);
StructType *Ty = StructType::get(
IRB.getInt32Ty(), PointerType::getUnqual(FnTy), NULL);
Constant *RuntimeCtorInit = ConstantStruct::get(
Ty, IRB.getInt32(Priority), F, NULL);
// Get the current set of static global constructors and add the new ctor
// to the list.
SmallVector<Constant *, 16> CurrentCtors;
if (GlobalVariable * GVCtor = M.getNamedGlobal(Array)) {
StructType *EltTy;
if (GlobalVariable *GVCtor = M.getNamedGlobal(Array)) {
// If there is a global_ctors array, use the existing struct type, which can
// have 2 or 3 fields.
ArrayType *ATy = cast<ArrayType>(GVCtor->getType()->getElementType());
EltTy = cast<StructType>(ATy->getElementType());
if (Constant *Init = GVCtor->getInitializer()) {
unsigned n = Init->getNumOperands();
CurrentCtors.reserve(n + 1);
@ -41,13 +41,26 @@ static void appendToGlobalArray(const char *Array,
CurrentCtors.push_back(cast<Constant>(Init->getOperand(i)));
}
GVCtor->eraseFromParent();
} else {
// Use a simple two-field struct if there isn't one already.
EltTy = StructType::get(IRB.getInt32Ty(), PointerType::getUnqual(FnTy),
nullptr);
}
// Build a 2 or 3 field global_ctor entry. We don't take a comdat key.
Constant *CSVals[3];
CSVals[0] = IRB.getInt32(Priority);
CSVals[1] = F;
// FIXME: Drop support for the two element form in LLVM 4.0.
if (EltTy->getNumElements() >= 3)
CSVals[2] = llvm::Constant::getNullValue(IRB.getInt8PtrTy());
Constant *RuntimeCtorInit =
ConstantStruct::get(EltTy, makeArrayRef(CSVals, EltTy->getNumElements()));
CurrentCtors.push_back(RuntimeCtorInit);
// Create a new initializer.
ArrayType *AT = ArrayType::get(RuntimeCtorInit->getType(),
CurrentCtors.size());
ArrayType *AT = ArrayType::get(EltTy, CurrentCtors.size());
Constant *NewInit = ConstantArray::get(AT, CurrentCtors);
// Create the new global variable and replace all uses of