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

[Paul Walker via Phabricator via llvm-commits]

paulwalker-arm 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 &&
----------------
efriedma wrote:
> 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?
I think so but will check if there's an architecture preferred answer and will report back.


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

https://reviews.llvm.org/D124325