[LLVMdev] Implementing an llvm.setreturnaddress intrinsic

[Mehrdad Niknami]

Hi,

I've been having some trouble implementing a new intrinsic for LLVM and I
was wondering if someone might know the answer.

LLVM has an llvm.returnaddress intrinsic, but for a specific project, I
need to be able to modify the return address of a function as well, so I'm
implementing a new intrinsic:
def int_setreturnaddress     : Intrinsic<[], [llvm_i32_ty, llvm_ptr_ty],
[]>;

And I'm using it as follows:
B.CreateCall2(
  Intrinsic::getDeclaration(M, Intrinsic::setreturnaddress),
  ConstantInt::get(Type::getInt32Ty(RI->getContext()), 0),
  B.CreateIntToPtr(ConstantInt::get(IntPtrTy, 0 /* testing */)),
RA->getReturnType()));

The problem I'm facing is that for some reason, my following line inside
X86TargetLowering::LowerOperation is never getting called:
case ISD::SETRETURNADDR:      return LowerSETRETURNADDR(Op, DAG);

This is despite the fact that I can confirm the following line inside
SelectionDAGBuilder::visitIntrinsicCall *is* getting called:
case Intrinsic::setreturnaddress:
    setValue(&I, DAG.getNode(ISD::SETRETURNADDR, sdl, TLI->getPointerTy(),
                             getValue(I.getArgOperand(0)),
                             getValue(I.getArgOperand(1))));
    return 0;

My best guess is that my code is being optimized out -- but I'm not sure
where or why.

Does anyone know why this might be happening?

Thank you!
Mehrdad
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