[PATCH] D124325: [AArch64][SVE] Support logical operation BIC with DestructiveBinary patterns

Wed Oct 19 10:39:05 PDT 2022

efriedma added inline comments.

================
Comment at: llvm/lib/Target/AArch64/AArch64ExpandPseudoInsts.cpp:592
+  // Zeros the lanes in z0 that aren't active in p0 with sequence movprfx
+  // z0.b, p0/z, z0.b; add z0.b, z0.b, #0;
+  if (DType == AArch64::DestructiveBinary &&
----------------
paulwalker-arm wrote:
> paulwalker-arm wrote:
> > Do any of the tests exercise this code?
> I don't believe this is safe because only predicated instructions are allowed to follow a predicated `movprfx` instruction. There's a section within
> ```
> https://developer.arm.com/documentation/ddi0487/latest/
> 
> Data processing - SVE
> -> Move operations
> --> Move prefix
> ```
> that details which instructions are allowed to follow a `movprfx`. 
Oh, oops, I misread the documentation.  Can we use `lsl z0.b, p0/m, z0.b, #0` instead?

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D124325/new/

https://reviews.llvm.org/D124325