[llvm] [SelectionDAG] Expand CTTZ_ELTS[_ZERO_POISON] and handle legalization (PR #188691)

[David Sherwood via llvm-commits]

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@@ -10115,22 +10115,24 @@ SDValue TargetLowering::expandVPCTTZElements(SDNode *N,
   return DAG.getNode(ISD::VP_REDUCE_UMIN, DL, ResVT, ExtEVL, Select, Mask, EVL);
 }
 
-SDValue TargetLowering::expandVectorFindLastActive(SDNode *N,
-                                                   SelectionDAG &DAG) const {
-  SDLoc DL(N);
-  SDValue Mask = N->getOperand(0);
+/// Returns a step vector that's guaranteed to fit the number of elements in \p
+/// Mask, as well as a type-legalized version of \p Mask.
+static std::pair<SDValue, SDValue> getLegalStepVector(SDValue Mask,
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david-arm wrote:

nit: you're also legalising the mask so perhaps the function should be called `getLegalMaskAndStepVector`?

https://github.com/llvm/llvm-project/pull/188691