[llvm] [ASan] Convert pointer-pair operands based on type (PR #218494)

[Thurston Dang via llvm-commits]

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thurstond wrote:

Instead of convertToIntptr below, would it better to keep CreatePointerCast but check `&& Ty->getElementType()->isPointerTy()` here?

https://github.com/llvm/llvm-project/pull/218494