[llvm] Fix performance bug in buildLocationList (PR #109343)

[Sriraman Tallam via llvm-commits]

tmsri wrote:

> Eyeballing this further, I was under the impression that this code was evaluating the validity of issuing a single-location in general, but I see now that's achieved by the earlier call to `validThroughout`. I see now that this is more about verifying the basic-block-section ranges are suitable to merge once the variable is identified as having a single-location, such as a constant value, is that correct?
> 

Yes, this is correct.  Even if it is not merged, it will produce something that is valid.



https://github.com/llvm/llvm-project/pull/109343