[PATCH] D72467: [WIP] Remove "mask" operand from shufflevector.

[Simon Moll via Phabricator via llvm-commits]

simoll added inline comments.


================
Comment at: llvm/lib/Analysis/InstructionSimplify.cpp:4413
                                         unsigned MaxRecurse) {
-  if (isa<UndefValue>(Mask))
+  if (all_of(Mask, [](int Elem) { return Elem == -1; }))
     return UndefValue::get(RetTy);
----------------
efriedma wrote:
> xbolva00 wrote:
> > maybe introduce new helper function to check if mask is "undef"?
> I could introduce ShuffleVectorInst::MaskIsAllUndef and ShuffleVectorInst::MaskIsAllZero, I guess.  Not sure how helpful that actually is for a predicate that can be expressed on one line anyway.
How about introducing the constant `UndefMaskElem` and changing this to something like:

`if (all_of(Mask, [](int Elem) { return Elem == UndefMaskElem; }))`

That would make it self-explanatory again and wouldn't expose the specific encoding of undef mask elems.



================
Comment at: llvm/lib/IR/Instructions.cpp:1871
     if (MaskElt == -1) {
-      NewMask[i] = UndefValue::get(Int32Ty);
+      NewMask[i] = -1;
       continue;
----------------
With the suggestion: `NewMask[i] = UndefMaskElem`


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D72467/new/

https://reviews.llvm.org/D72467