[NFC][IndVarSimplify] remove duplicate code in widenWithVariantLoadUseCodegen

[zhongduo]

Summary

Duplicate code in widenWithVariantLoadUseCodegen is removed and also use assert to check unknown extension type as it should be filtered out by the pre condition check before calling this function.

[efriedma]

LGTM. Do you have commit access?

llvm/lib/Transforms/Scalar/IndVarSimplify.cpp

void WidenIV::widenWithVariantLoadUseCodegen(NarrowIVDefUse DU) {
 
   auto *NarrowBO = cast<BinaryOperator>(NarrowUse);
   auto *WideBO = BinaryOperator::Create(NarrowBO->getOpcode(), LHS, RHS,
                                         NarrowBO->getName());
   IRBuilder<> Builder(NarrowUse);
   Builder.Insert(WideBO);
   WideBO->copyIRFlags(NarrowBO);
 
-  if (ExtKind == SignExtended)
-    ExtendKindMap[NarrowUse] = SignExtended;
-  else
-    ExtendKindMap[NarrowUse] = ZeroExtended;
+  assert(ExtKind != Unknown && "Unknown ExtKind not handled");
+
+  ExtendKindMap[NarrowUse] = ExtKind;
 
-  // Update the Use.
-  if (ExtKind == SignExtended) {
-    for (Use &U : NarrowUse->uses()) {
-      SExtInst *User = dyn_cast<SExtInst>(U.getUser());
-      if (User && User->getType() == WideType) {
-        LLVM_DEBUG(dbgs() << "INDVARS: eliminating " << *User << " replaced by "
-                          << *WideBO << "\n");
-        ++NumElimExt;
-        User->replaceAllUsesWith(WideBO);
-        DeadInsts.emplace_back(User);
-      }
-    }
-  } else { // ExtKind == ZeroExtended
-    for (Use &U : NarrowUse->uses()) {
-      ZExtInst *User = dyn_cast<ZExtInst>(U.getUser());
-      if (User && User->getType() == WideType) {
-        LLVM_DEBUG(dbgs() << "INDVARS: eliminating " << *User << " replaced by "
-                          << *WideBO << "\n");
-        ++NumElimExt;
-        User->replaceAllUsesWith(WideBO);
-        DeadInsts.emplace_back(User);
-      }
-    }
-  }
-}
+    Instruction *User = nullptr;
+    if (ExtKind == SignExtended)
+      User = dyn_cast<SExtInst>(U.getUser());
+    else
+      User = dyn_cast<ZExtInst>(U.getUser());
 
 /// Determine whether an individual user of the narrow IV can be widened. If so,
 /// return the wide clone of the user.
 Instruction *WidenIV::widenIVUse(NarrowIVDefUse DU, SCEVExpander &Rewriter) {
   assert(ExtendKindMap.count(DU.NarrowDef) &&
          "Should already know the kind of extension used to widen NarrowDef");
 
   // Stop traversing the def-use chain at inner-loop phis or post-loop phis.