- // Aggregate types can't be cast, but are legal argument types, so we have
- // to handle them differently. We use an extract/insert pair as a
- // lightweight method to achieve the same goal.
- if (isa<StructType>(Ty) || isa<ArrayType>(Ty) || isa<VectorType>(Ty)) {
- Instruction *EI = ExtractValueInst::Create(AI, 0, "", AfterAllocaInsPt);
- Instruction *NI = InsertValueInst::Create(AI, EI, 0);
- NI->insertAfter(EI);
- AI->replaceAllUsesWith(NI);
-
- // Set the operand of the instructions back to the AllocaInst.
- EI->setOperand(0, AI);
- NI->setOperand(0, AI);
- } else {
- // This is always a no-op cast because we're casting AI to AI->getType()
- // so src and destination types are identical. BitCast is the only
- // possibility.
- CastInst *NC =
- new BitCastInst(AI, AI->getType(), AI->getName() + ".tmp",
- AfterAllocaInsPt);
- AI->replaceAllUsesWith(NC);
-
- // Set the operand of the cast instruction back to the AllocaInst.
- // Normally it's forbidden to replace a CastInst's operand because it
- // could cause the opcode to reflect an illegal conversion. However, we're
- // replacing it here with the same value it was constructed with. We do
- // this because the above replaceAllUsesWith() clobbered the operand, but
- // we want this one to remain.
- NC->setOperand(0, AI);
- }
+ // Use 'select i8 true, %arg, undef' to simulate a 'no-op' instruction.
+ Value *TrueValue = ConstantInt::getTrue(F.getContext());
+ Value *UndefValue = UndefValue::get(Ty);
+ Instruction *SI = SelectInst::Create(TrueValue, AI, UndefValue,
+ AI->getName() + ".tmp",
+ AfterAllocaInsPt);
+ AI->replaceAllUsesWith(SI);
+
+ // Reset the operand, because it was clobbered by the RAUW above.
+ SI->setOperand(1, AI);