[clang] [clang][Interp] Support AddOffset with 128bit offsets (PR #68679)

[Aaron Ballman via cfe-commits]

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@@ -1437,7 +1437,7 @@ bool OffsetHelper(InterpState &S, CodePtr OpPC, const T &Offset,
     return false;
   };
 
-  unsigned MaxOffset = MaxIndex - Ptr.getIndex();
+  T MaxOffset = T::from(MaxIndex - Ptr.getIndex(), Offset.bitWidth());
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AaronBallman wrote:

I think we should make the math operate on a `T` consistently, especially given that `Offset` and `Index` are already a `T`. The mixture of types is a bit of a code smell IMO.

https://github.com/llvm/llvm-project/pull/68679