[PATCH] D117451: [MCA] Proposing the InstrPostProcess:modifyInstrDesc() method.

[Min-Yih Hsu via Phabricator via llvm-commits]

myhsu added inline comments.


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Comment at: llvm/lib/MCA/InstrBuilder.cpp:736
   if (!IsVariadic && !IsVariant) {
     Descriptors[MCI.getOpcode()] = std::move(ID);
     return *Descriptors[MCI.getOpcode()];
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In the cases where `Modified` is true (and it's not variadic / variant), should we still cache InstrDesc by the opcode?
Or more specifically, can `modifyInstrDesc` create different changes for two separate MCInst-s that has the same opcode? (e.g. I'm only changing the MayStore flag in an `ADD32` MCInst if it's preceded by a `LD16`, given the fact that IPP can have state)
Because if that's true, I think the `Descriptors` cache here will return a stale / incorrect InstrDesc.

I understand that in your motivating example ("...where we wanted to set the RetireOOO flag for all of our targets, but we didn't want to have to modify the tablegen for every single one of those targets...") you're probably making homogeneous changes across all MCInst-s that have the same opcode but I feel like there needs to be some clarifications on the model of `modifyInstrDesc`.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D117451/new/

https://reviews.llvm.org/D117451