[VP] Remove createStepVector implementation and use IRBuilderBase::CreateStepVector instead. NFC (#122868)

Author: LiqinWeng

llvm/lib/CodeGen/ExpandVectorPredication.cpp

@@ -136,17 +136,6 @@ namespace {
 struct CachingVPExpander {
   const TargetTransformInfo &TTI;
 
-  /// \returns A (fixed length) vector with ascending integer indices
-  /// (<0, 1, ..., NumElems-1>).
-  /// \p Builder
-  ///    Used for instruction creation.
-  /// \p LaneTy
-  ///    Integer element type of the result vector.
-  /// \p NumElems
-  ///    Number of vector elements.
-  Value *createStepVector(IRBuilder<> &Builder, Type *LaneTy,
-                          unsigned NumElems);
-
   /// \returns A bitmask that is true where the lane position is less-than \p
   /// EVLParam
   ///
@@ -216,17 +205,6 @@ struct CachingVPExpander {
 
 //// CachingVPExpander {
 
-Value *CachingVPExpander::createStepVector(IRBuilder<> &Builder, Type *LaneTy,
-                                           unsigned NumElems) {
-  // TODO add caching
-  SmallVector<Constant *, 16> ConstElems;
-
-  for (unsigned Idx = 0; Idx < NumElems; ++Idx)
-    ConstElems.push_back(ConstantInt::get(LaneTy, Idx, false));
-
-  return ConstantVector::get(ConstElems);
-}
-
 Value *CachingVPExpander::convertEVLToMask(IRBuilder<> &Builder,
                                            Value *EVLParam,
                                            ElementCount ElemCount) {
@@ -245,7 +223,7 @@ Value *CachingVPExpander::convertEVLToMask(IRBuilder<> &Builder,
   Type *LaneTy = EVLParam->getType();
   unsigned NumElems = ElemCount.getFixedValue();
   Value *VLSplat = Builder.CreateVectorSplat(NumElems, EVLParam);
-  Value *IdxVec = createStepVector(Builder, LaneTy, NumElems);
+  Value *IdxVec = Builder.CreateStepVector(VectorType::get(LaneTy, ElemCount));
   return Builder.CreateICmp(CmpInst::ICMP_ULT, IdxVec, VLSplat);
 }