Get a `CGM.getIntrinsic`-like for `LLVMIntrinsicCallOp`

[bcardosolopes]

Not for this PR, but something to note here: in OG CGM.getIntrinsic seems to be able to figure out the type of the intrinsic, we should do the same in CIR to make writing these easier:

  case X86::BI__builtin_ia32_rdtscp: {
    Value *Call = Builder.CreateCall(CGM.getIntrinsic(Intrinsic::x86_rdtscp));
    Builder.CreateDefaultAlignedStore(Builder.CreateExtractValue(Call, 1),
                                      Ops[0]);
    return Builder.CreateExtractValue(Call, 0);
  }

Originally posted by @bcardosolopes in #1686 (comment)

[RiverDave]

@bcardosolopes I'll take on this. Few things though: Since CGM.getIntrinsic wraps Intrinsic::getOrInsertDeclaration() and helpers rely on Codegen Specifics (like llvm::Module), I guess the way forward would be to replicate what's done in llvm/include/llvm/IR/Intrinsics.h? This class seems a bit bulky, so I wanted to double check first. Let me know if there's any other advice for me to carry on forward.

[RiverDave]

Something else @bcardosolopes , I've opened a draft: #1710. I've highlighted the major roadblocks and limitations I've found so far, would appreciate any feedback :)

[bcardosolopes]

@RiverDave I was out on extended holiday on the US, will take a look soon. It's possible you could use tablegen to generate the boilerplate necessary (instead of replicating things)

[RiverDave]

@RiverDave I was out on extended holiday on the US, will take a look soon. It's possible you could use tablegen to generate the boilerplate necessary (instead of replicating things)

No worries at all, enjoy your vacation 😄