[PATCH] D89540: [SCEV] Index type usually is, but is not guaranteed to be, equal to the pointer bit width

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

In D89540#2335050 <https://reviews.llvm.org/D89540#2335050>, @efriedma wrote:

> I'm not sure I completely understand the history from https://reviews.llvm.org/D42123.  But I think the idea is that for pointer-type SCEVs, we want to do SCEV arithmetic using the index type because the other bits aren't relevant: from my understanding, they don't participate in pointer arithmetic.
>
> So I think the right solution is to leave this code alone.  And maybe don't create SCEVPtrToInt expressions for ptrtoint operations on pointers where getIndexTypeSizeInBits() isn't equal to getTypeSizeInBits(), at least initially, since it's sort of tricky to reason about.

I question sanity of that approach.
That being said, then perhaps D89456 <https://reviews.llvm.org/D89456> simply should also pretend that the pointer's high bits don't exist if they don't matter for us?


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