[JIT] ARM64 - Overflow check optimizations for division #82924
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…tant that is a not a min value
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Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch, @kunalspathak Issue DetailsWill resolve #46010 At the moment, I haven't got rid of the redundant branch operations yet.
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@dotnet/jit-contrib @kunalspathak This is ready. Straight-forward change, should be an easy review. Diffs |
src/coreclr/jit/morph.cpp
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NOTE: this still leaves overflow block alive if it's unused but presumably it's a different issue
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Hhm, won't it be dead code eliminated?
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Throw helper blocks are marked as no-remove. This is because they aren't rooted in the normal flowgraph (the edges from the throwing nodes to the throw helper blocks are implicit).
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Hhm, won't it be dead code eliminated?
these blocks are special, they have BBF_DONT_REMOVE or something like that. We spawn them early in importer/morph and then tie to corresponding divisions if needed, it's too late to remove them in codegen
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I'm hopeful that this PR will resolve those cases as it's already happening today.
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| // true if the given tree is known to never be negative one | ||
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| bool GenTree::IsNeverNegativeOne(Compiler* comp) const |
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this helper is only needed for division in one place it seems?
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It's only in one place, but it does help make things clean.
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@dotnet/jit-contrib @BruceForstall This is ready again. Diffs |
Co-authored-by: SingleAccretion <[email protected]>
…Flags. Use GetExceptionSetFlags to determine to add div-by-zero or overflow blocks for arm64.
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Thank you all for the feedback. The PR feels a lot better. Since @SingleAccretion pointed me to I wonder if there are any more duplicate checks. |
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@dotnet/jit-contrib ready again. Got more wins in full-opts compared to before: diffs |
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/azp run runtime-coreclr jitstress gcstress |
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/azp run runtime-coreclr jitstress |
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Azure Pipelines successfully started running 1 pipeline(s). |
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/azp run runtime-coreclr gcstress |
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No pipelines are associated with this pull request. |
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/azp run fuzzlyn |
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Azure Pipelines successfully started running 1 pipeline(s). |
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@jakobbotsch - I think it's fine that we do this optimization in min-opts, we were already doing it before. It's not going to hurt the debugging experience for users as its all generated internally; I don't see how this would impact anyone. |
Description
Resolves #46010
This PR will not emit an arithmetic exception block if we know the dividend of a division operation is constant and not a MinValue.
This PR will also shorten the emitted code when testing for an overflow of a division operation.
Acceptance Criteria