[NFC][IR] Add CreateCountTrailingZeroElems helper (#106711)

The LoopIdiomVectorize pass already creates calls to the intrinsic
experimental_cttz_elts, but PR #88385 will start calling this more
too so I've created a helper for it.

Author: david-arm

llvm/include/llvm/IR/IRBuilder.h

@@ -1079,6 +1079,15 @@ class IRBuilderBase {
                            nullptr, Name);
   }
 
+  /// Create a call to llvm.experimental_cttz_elts
+  Value *CreateCountTrailingZeroElems(Type *ResTy, Value *Mask,
+                                      bool ZeroIsPoison = true,
+                                      const Twine &Name = "") {
+    return CreateIntrinsic(Intrinsic::experimental_cttz_elts,
+                           {ResTy, Mask->getType()},
+                           {Mask, getInt1(ZeroIsPoison)}, nullptr, Name);
+  }
+
 private:
   /// Create a call to a masked intrinsic with given Id.
   CallInst *CreateMaskedIntrinsic(Intrinsic::ID Id, ArrayRef<Value *> Ops,

llvm/lib/Transforms/Vectorize/LoopIdiomVectorize.cpp

@@ -470,9 +470,7 @@ Value *LoopIdiomVectorize::createMaskedFindMismatch(
   VectorFoundIndex->addIncoming(VectorIndexPhi, VectorLoopStartBlock);
 
   Value *PredMatchCmp = Builder.CreateAnd(LastLoopPred, FoundPred);
-  Value *Ctz = Builder.CreateIntrinsic(
-      Intrinsic::experimental_cttz_elts, {ResType, PredMatchCmp->getType()},
-      {PredMatchCmp, /*ZeroIsPoison=*/Builder.getInt1(true)});
+  Value *Ctz = Builder.CreateCountTrailingZeroElems(ResType, PredMatchCmp);
   Ctz = Builder.CreateZExt(Ctz, I64Type);
   Value *VectorLoopRes64 = Builder.CreateAdd(VectorFoundIndex, Ctz, "",
                                              /*HasNUW=*/true, /*HasNSW=*/true);