[PATCH] D98264: [AArch64] Implement __rndr, __rndrrs intrinsics

[Sjoerd Meijer via Phabricator via llvm-commits]

SjoerdMeijer added inline comments.


================
Comment at: llvm/lib/Target/AArch64/AArch64InstrFormats.td:1495
   let DecoderNamespace = "Fallback";
+  let Defs = [NZCV];
 }
----------------
dmgreen wrote:
> SjoerdMeijer wrote:
> > Do all MRS instructions do this?
> No, but some do and it's not obvious which ones do and don't. I think it should be reasonable to always def NZCV here, even if they are just dead. It should be very rare that it would be beneficial for NZCV to be live across a MRS instruction.
True, but since creating another definition is cheap, what would the cons be of:

  class MRS_NZCV : MRSI {
    ..
    let Defs = [NZCV];
  }

The way I look at it is that the description would be more accurate?


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D98264/new/

https://reviews.llvm.org/D98264