//
// Method: visitAllocaInst()
//
// Description:
// This method instruments an alloca instruction so that it is zero'ed out
// before any data is loaded from it.
//
void
InitAllocas::visitAllocaInst (AllocaInst & AI) {
//
// Scan for a place to insert the instruction to initialize the
// allocated memory.
//
Instruction * InsertPt = getInsertionPoint (AI);
//
// Zero the alloca with a memset. If this is done more efficiently with stores
// SelectionDAG will lower it appropriately based on target information.
//
const DataLayout & TD = AI.getModule()->getDataLayout();
//
// Get various types that we'll need.
//
Type * Int1Type = IntegerType::getInt1Ty(AI.getContext());
Type * Int8Type = IntegerType::getInt8Ty(AI.getContext());
Type * Int32Type = IntegerType::getInt32Ty(AI.getContext());
Type * VoidPtrType = getVoidPtrType (AI.getContext());
Type * AllocType = AI.getAllocatedType();
//
// Create a call to memset.
//
Module * M = AI.getParent()->getParent()->getParent();
Function * Memset = cast<Function>(M->getFunction ("llvm.memset.p0i8.i32"));
std::vector<Value *> args;
args.push_back (castTo (&AI, VoidPtrType, AI.getName().str(), InsertPt));
args.push_back (ConstantInt::get(Int8Type, 0));
args.push_back (ConstantInt::get(Int32Type,TD.getTypeAllocSize(AllocType)));
args.push_back (ConstantInt::get(Int32Type,
TD.getABITypeAlignment(AllocType)));
args.push_back (ConstantInt::get(Int1Type, 0));
CallInst::Create (Memset, args, "", InsertPt);
//
// Update statistics.
//
++InitedAllocas;
return;
}
