[PATCH] D83236: [DWARF] Add cutoff guarding validThroughout to avoid near-quadratic behaviour

[David Blaikie via Phabricator via llvm-commits]

dblaikie added a comment.

In D83236#2135647 <https://reviews.llvm.org/D83236#2135647>, @jmorse wrote:

> In D83236#2133902 <https://reviews.llvm.org/D83236#2133902>, @dblaikie wrote:
>
> > Could the algorithm be changed to do validThroughout of all variable fragments in a single pass together?
>
>
> This is probably do-able, although I'm generally unfamiliar with the DWARF emission code. Right now we iterate over variable entities and call validThroughout for those that might be single-locations; we would need to pivot to iterate over variable entities collecting those that _might_ be single-location, then calling validThroughout once for that set. My preference is to fold this problem into the work that @Orlando is doing though -- his patch is already solving this problem (intersection of scope and variable-location range) in one context, we should be able to re-purpose it to solve this one too.
>
> (Most of my motivation for this patch is the upcoming branch for LLVM11, I'd like to get a limit on this, then work towards doing it more efficiently)


Fair enough. Perhaps a clear FIXME or the like (suggesting that this should be obsoleted by @orlando 's work (& ensuring they're aware that this is something that should be considered in the replacement design)?


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