[llvm] prefer isa_and_nonnull over v && isa

Use `isa_and_nonnull<T>(v)` instead of `v && isa<T>(v)`, where `v` is
evaluated twice in the latter.

Author: VoltrexKeyva

llvm/lib/Analysis/ConstantFolding.cpp

@@ -82,7 +82,7 @@ static Constant *foldConstVectorToAPInt(APInt &Result, Type *DestTy,
     else
       Element = C->getAggregateElement(i);
 
-    if (Element && isa<UndefValue>(Element)) {
+    if (isa_and_nonnull<UndefValue>(Element)) {
       Result <<= BitShift;
       continue;
     }
@@ -218,7 +218,7 @@ Constant *FoldBitCast(Constant *C, Type *DestTy, const DataLayout &DL) {
       unsigned ShiftAmt = isLittleEndian ? 0 : SrcBitSize*(Ratio-1);
       for (unsigned j = 0; j != Ratio; ++j) {
         Constant *Src = C->getAggregateElement(SrcElt++);
-        if (Src && isa<UndefValue>(Src))
+        if (isa_and_nonnull<UndefValue>(Src))
           Src = Constant::getNullValue(
               cast<VectorType>(C->getType())->getElementType());
         else