JIT: Only process regular succs for end-of-block PHI insertions #94958
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When we saw a def we were only adding phi args to enclosing handlers, but this misses the special case of throws inside filters, where control can flow to enclosed handlers. Fix dotnet#94954
When inserting PHI args into successors as part of getting to the end of a block in SSA we really only need to visit regular successors. EH successors are handled on entry to the try and eagerly when we see stores. This also means we can avoid the search to check for duplicate (pred, SSA num) pairs in many cases. These should really only be possible for handlers. There is one questionable case here which is regular control flow from the end of filters into enclosed handlers. I need to think a bit about that... I do not think we have correctness problems since we know that only happens if we came from inside the try, but I dislike that we won't have an explicit phi arg with the filter as a pred.
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Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch Issue DetailsWhen inserting PHI args into successors as part of getting to the end of This also means we can avoid the search to check for duplicate (pred, There is one questionable case here which is regular control flow from
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TP improvement was around 0.1%, which doesn't seem worth the trouble. |
When inserting PHI args into successors as part of getting to the end of
a block in SSA we really only need to visit regular successors. EH
successors are handled on entry to the try and eagerly when we see
stores.
This also means we can avoid the search to check for duplicate (pred,
SSA num) pairs in many cases. These should really only be possible for
handlers.
There is one questionable case here which is regular control flow from
the end of filters into enclosed handlers. I need to think a bit about
that... I do not think we have correctness problems since we know that
only happens if we came from inside the try, but I dislike that we won't
have an explicit phi arg with the filter as a pred.