[llvm] [DirectX] Address PR comments to #131221 (PR #131706)

[Farzon Lotfi via llvm-commits]

================
@@ -61,47 +43,66 @@ static void fixI8TruncUseChain(Instruction &I,
         // Note: options here are sext or sextOrTrunc.
         // Since i8 isn't supported, we assume new values
         // will always have a higher bitness.
+        assert(NewBitWidth > Value.getBitWidth() &&
+               "Replacement's BitWidth should be larger than Current.");
         APInt NewValue = Value.sext(NewBitWidth);
         NewOperands.push_back(ConstantInt::get(InstrType, NewValue));
       } else {
         assert(!Op->getType()->isIntegerTy(8));
         NewOperands.push_back(Op);
       }
     }
-
-    Value *NewInst = nullptr;
-    if (auto *BO = dyn_cast<BinaryOperator>(&I)) {
-      NewInst =
-          Builder.CreateBinOp(BO->getOpcode(), NewOperands[0], NewOperands[1]);
-
-      if (auto *OBO = dyn_cast<OverflowingBinaryOperator>(&I)) {
-        if (OBO->hasNoSignedWrap())
-          cast<BinaryOperator>(NewInst)->setHasNoSignedWrap();
-        if (OBO->hasNoUnsignedWrap())
-          cast<BinaryOperator>(NewInst)->setHasNoUnsignedWrap();
-      }
-    } else if (Cmp) {
-      NewInst = Builder.CreateCmp(Cmp->getPredicate(), NewOperands[0],
-                                  NewOperands[1]);
-      Cmp->replaceAllUsesWith(NewInst);
+  };
+  IRBuilder<> Builder(&I);
+  if (auto *Trunc = dyn_cast<TruncInst>(&I)) {
+    if (Trunc->getDestTy()->isIntegerTy(8)) {
+      ReplacedValues[Trunc] = Trunc->getOperand(0);
+      ToRemove.push_back(Trunc);
     }
-
-    if (NewInst) {
-      ReplacedValues[&I] = NewInst;
-      ToRemove.push(&I);
+  }
+  Value *NewInst = nullptr;
+  if (auto *BO = dyn_cast<BinaryOperator>(&I)) {
+    if (!I.getType()->isIntegerTy(8))
+      return;
+    SmallVector<Value *> NewOperands;
+    ProcessOperands(NewOperands);
+    NewInst =
+        Builder.CreateBinOp(BO->getOpcode(), NewOperands[0], NewOperands[1]);
+    if (auto *OBO = dyn_cast<OverflowingBinaryOperator>(&I)) {
+      if (OBO->hasNoSignedWrap())
+        cast<BinaryOperator>(NewInst)->setHasNoSignedWrap();
+      if (OBO->hasNoUnsignedWrap())
+        cast<BinaryOperator>(NewInst)->setHasNoUnsignedWrap();
     }
----------------
farzonl wrote:

if I return here i need to do 
```cpp
     ReplacedValues[&I] = NewInst;
    ToRemove.push_back(&I);
```
twice. once for cmp and once for BinaryOperator

https://github.com/llvm/llvm-project/pull/131706