[IR] Remove ZExtOperator (NFC)

Now that zext constant expressions are no longer supported,
ZExtInst should be used instead.

Author: nikic

llvm/include/llvm/IR/Operator.h

@@ -367,8 +367,6 @@ class LShrOperator
   : public ConcreteOperator<PossiblyExactOperator, Instruction::LShr> {
 };
 
-class ZExtOperator : public ConcreteOperator<Operator, Instruction::ZExt> {};
-
 class GEPOperator
   : public ConcreteOperator<Operator, Instruction::GetElementPtr> {
   friend class GetElementPtrInst;

llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp

@@ -5574,8 +5574,8 @@ Instruction *InstCombinerImpl::foldICmpWithZextOrSext(ICmpInst &ICmp) {
   // icmp Pred (ext X), (ext Y)
   Value *Y;
   if (match(ICmp.getOperand(1), m_ZExtOrSExt(m_Value(Y)))) {
-    bool IsZext0 = isa<ZExtOperator>(ICmp.getOperand(0));
-    bool IsZext1 = isa<ZExtOperator>(ICmp.getOperand(1));
+    bool IsZext0 = isa<ZExtInst>(ICmp.getOperand(0));
+    bool IsZext1 = isa<ZExtInst>(ICmp.getOperand(1));
 
     if (IsZext0 != IsZext1) {
         // If X and Y and both i1
@@ -5834,8 +5834,8 @@ static Instruction *processUMulZExtIdiom(ICmpInst &I, Value *MulVal,
     return nullptr;
   assert(MulInstr->getOpcode() == Instruction::Mul);
 
-  auto *LHS = cast<ZExtOperator>(MulInstr->getOperand(0)),
-       *RHS = cast<ZExtOperator>(MulInstr->getOperand(1));
+  auto *LHS = cast<ZExtInst>(MulInstr->getOperand(0)),
+       *RHS = cast<ZExtInst>(MulInstr->getOperand(1));
   assert(LHS->getOpcode() == Instruction::ZExt);
   assert(RHS->getOpcode() == Instruction::ZExt);
   Value *A = LHS->getOperand(0), *B = RHS->getOperand(0);

llvm/lib/Transforms/InstCombine/InstructionCombining.cpp

@@ -916,7 +916,7 @@ InstCombinerImpl::foldBinOpOfSelectAndCastOfSelectCondition(BinaryOperator &I) {
 
   auto NewFoldedConst = [&](bool IsTrueArm, Value *V) {
     bool IsCastOpRHS = (CastOp == RHS);
-    bool IsZExt = isa<ZExtOperator>(CastOp);
+    bool IsZExt = isa<ZExtInst>(CastOp);
     Constant *C;
 
     if (IsTrueArm) {