[compiler-rt] [TSan] Fix p == end == ShadowMem::end in ShadowSet (PR #144994)

[Thurston Dang via llvm-commits]

https://github.com/thurstond approved this pull request.

Meta comment: LLVM generally encourages reverting broken changes rather than fixing-forward:

'Any time you learn of a serious problem with a change, you should revert it. We strongly encourage “revert to green” as opposed to “fixing forward”. We encourage reverting first, investigating offline, and then reapplying the fixed patch - possibly after another round of review if warranted.' (https://llvm.org/docs/DeveloperPolicy.html)

If the fix was trivial then a fix-forward would be fine (and could skip even review). This fix is a bit finicky (it requires reasoning about all the calls to ShadowSet) so I wouldn't consider it a trivial fix-forward.

That said, if you are confident this fixes the issue (and have re-run the failing tests?), this looks good to me.

https://github.com/llvm/llvm-project/pull/144994