[PATCH] D140412: [DebugInfo] Unify location selection logic for values in InstrRefBasedImpl

[Stephen Tozer via Phabricator via llvm-commits]

StephenTozer added a comment.

In D140412#4008377 <https://reviews.llvm.org/D140412#4008377>, @jmorse wrote:

> Slightly twitchy about there being a zero LocIdx -- I think I tried to suppress there being any default-constructed LocIdxes out there. On the other hand, it comes with a sentinel value attached, so it's no big deal.

In this case the reasoning was that `LocIdx` is 32 bits that only uses 24 for the location, so the sentinel value can be `UINT_MAX`; since `LocationAndQuality` uses just 24 bits for the location, I figured there wasn't //any// good value that could be assigned to the location bits, while the quality bits already tell us whether the location bits mean anything or not.


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