if (MadeChange) return &GEP;
}
- // Check to see if the inputs to the PHI node are getelementptr instructions.
- if (PHINode *PN = dyn_cast<PHINode>(PtrOp)) {
- GetElementPtrInst *Op1 = dyn_cast<GetElementPtrInst>(PN->getOperand(0));
- if (!Op1)
- return nullptr;
-
- signed DI = -1;
-
- for (auto I = PN->op_begin()+1, E = PN->op_end(); I !=E; ++I) {
- GetElementPtrInst *Op2 = dyn_cast<GetElementPtrInst>(*I);
- if (!Op2 || Op1->getNumOperands() != Op2->getNumOperands())
- return nullptr;
-
- for (unsigned J = 0, F = Op1->getNumOperands(); J != F; ++J) {
- if (Op1->getOperand(J)->getType() != Op2->getOperand(J)->getType())
- return nullptr;
-
- if (Op1->getOperand(J) != Op2->getOperand(J)) {
- if (DI == -1) {
- // We have not seen any differences yet in the GEPs feeding the
- // PHI yet, so we record this one if it is allowed to be a
- // variable.
-
- // The first two arguments can vary for any GEP, the rest have to be
- // static for struct slots
- if (J > 1) {
- SmallVector<Value*, 8> Idxs(GEP.idx_begin(), GEP.idx_begin()+J);
- Type *Ty =
- GetElementPtrInst::getIndexedType(Op1->getOperand(0)->getType(),
- Idxs);
- if (Ty->isStructTy())
- return nullptr;
- }
-
- DI = J;
- } else {
- // The GEP is different by more than one input. While this could be
- // extended to support GEPs that vary by more than one variable it
- // doesn't make sense since it greatly increases the complexity and
- // would result in an R+R+R addressing mode which no backend
- // directly supports and would need to be broken into several
- // simpler instructions anyway.
- return nullptr;
- }
- }
- }
- }
-
- GetElementPtrInst *NewGEP = cast<GetElementPtrInst>(Op1->clone());
-
- if (DI == -1) {
- // All the GEPs feeding the PHI are identical. Clone one down into our
- // BB so that it can be merged with the current GEP.
- GEP.getParent()->getInstList().insert(GEP.getParent()->getFirstNonPHI(),
- NewGEP);
- } else {
- // All the GEPs feeding the PHI differ at a single offset. Clone a GEP
- // into the current block so it can be merged, and create a new PHI to
- // set that index.
- Instruction *InsertPt = Builder->GetInsertPoint();
- Builder->SetInsertPoint(PN);
- PHINode *NewPN = Builder->CreatePHI(Op1->getOperand(DI)->getType(),
- PN->getNumOperands());
- Builder->SetInsertPoint(InsertPt);
-
- for (auto &I : PN->operands())
- NewPN->addIncoming(cast<GEPOperator>(I)->getOperand(DI),
- PN->getIncomingBlock(I));
-
- NewGEP->setOperand(DI, NewPN);
- GEP.getParent()->getInstList().insert(GEP.getParent()->getFirstNonPHI(),
- NewGEP);
- NewGEP->setOperand(DI, NewPN);
- }
-
- GEP.setOperand(0, NewGEP);
- PtrOp = NewGEP;
- }
-
// Combine Indices - If the source pointer to this getelementptr instruction
// is a getelementptr instruction, combine the indices of the two
// getelementptr instructions into a single instruction.