-/// FindScalarElement - Given a vector and an element number, see if the scalar
-/// value is already around as a register, for example if it were inserted then
-/// extracted from the vector.
-static Value *FindScalarElement(Value *V, unsigned EltNo) {
- assert(V->getType()->isVectorTy() && "Not looking at a vector?");
- VectorType *VTy = cast<VectorType>(V->getType());
- unsigned Width = VTy->getNumElements();
- if (EltNo >= Width) // Out of range access.
- return UndefValue::get(VTy->getElementType());
-
- if (Constant *C = dyn_cast<Constant>(V))
- return C->getAggregateElement(EltNo);
-
- if (InsertElementInst *III = dyn_cast<InsertElementInst>(V)) {
- // If this is an insert to a variable element, we don't know what it is.
- if (!isa<ConstantInt>(III->getOperand(2)))
- return nullptr;
- unsigned IIElt = cast<ConstantInt>(III->getOperand(2))->getZExtValue();
-
- // If this is an insert to the element we are looking for, return the
- // inserted value.
- if (EltNo == IIElt)
- return III->getOperand(1);
-
- // Otherwise, the insertelement doesn't modify the value, recurse on its
- // vector input.
- return FindScalarElement(III->getOperand(0), EltNo);
- }
-
- if (ShuffleVectorInst *SVI = dyn_cast<ShuffleVectorInst>(V)) {
- unsigned LHSWidth = SVI->getOperand(0)->getType()->getVectorNumElements();
- int InEl = SVI->getMaskValue(EltNo);
- if (InEl < 0)
- return UndefValue::get(VTy->getElementType());
- if (InEl < (int)LHSWidth)
- return FindScalarElement(SVI->getOperand(0), InEl);
- return FindScalarElement(SVI->getOperand(1), InEl - LHSWidth);
- }
-
- // Extract a value from a vector add operation with a constant zero.
- Value *Val = nullptr; Constant *Con = nullptr;
- if (match(V, m_Add(m_Value(Val), m_Constant(Con)))) {
- if (Con->getAggregateElement(EltNo)->isNullValue())
- return FindScalarElement(Val, EltNo);
- }
-
- // Otherwise, we don't know.
- return nullptr;
-}
-