Mask was modified to work properly even if the pointer size is bigger than 64bits.

llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp

if (!GEP->isInBounds()) {
     // index down like the GEP would do implicitly.  We don't have to do this
     // for an inbounds GEP because the index can't be out of range.
     Type *IntPtrTy = DL.getIntPtrType(GEP->getType());
     unsigned PtrSize = IntPtrTy->getIntegerBitWidth();
     if (Idx->getType()->getPrimitiveSizeInBits().getFixedSize() > PtrSize)
       Idx = Builder.CreateTrunc(Idx, IntPtrTy);
 
     unsigned ElementSize =
         DL.getTypeAllocSize(Init->getType()->getArrayElementType());
 
-
     // If inbounds keyword is not present, Idx * ElementSize can overflow.
     // Let's assume that ElementSize is 2 and the wanted value is at offset 0.
     // Then, there are two possible values for Idx to match offset 0:
     // 0x00..00, 0x80..00.
     // Emitting 'icmp eq Idx, 0' isn't correct in this case because the
     // comparison is false if Idx was 0x80..00.
     // We need to erase the highest countTrailingZeros(ElementSize) bits of Idx.
     if (countTrailingZeros(ElementSize) != 0) {