Revert "Updated VPlanAnalysis"

This reverts commit 0534955.

Author: Mel-Chen

llvm/lib/Transforms/Vectorize/VPlanAnalysis.cpp

@@ -50,7 +50,6 @@ Type *VPTypeAnalysis::inferScalarTypeForRecipe(const VPInstruction *R) {
     return SetResultTyFromOp();
 
   switch (Opcode) {
-  case VPInstruction::MergeUntilPivot:
   case Instruction::Select: {
     Type *ResTy = inferScalarType(R->getOperand(1));
     VPValue *OtherV = R->getOperand(2);