C++: Further performance improvement for the null termination queries #7018
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MathiasVP
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Nov 2, 2021
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| mayAddNullTerminatorHelper(e, va, v0) and | ||
| mayAddNullTerminator(pragma[only_bind_into](e0), pragma[only_bind_into](v0.getAnAccess())) and |
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Ah, I see why this speeds it up. Previously, we were computing an SCC consisting of {mayAddNullTerminator, mayAddNullTerminatorHelper}, but now we're computing mayAddNullTerminatorHelper first, and then evaluating an SCC just containing mayAddNullTerminator. So this doesn't change any query results. Is that a correct description of what's going on?
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Yes, that's my understanding as well. The tricky part is that we may be computing a bigger (less constrained) mayAddNullTerminatorHelper relation in the first place, but I haven't seen that be a problem.
Co-authored-by: Mathias Vorreiter Pedersen <mathiasvp@github.com>
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Follow-up to #6915.
The goal here was to eliminate the mutual recursion between
mayAddNullTerminatorandmayAddNullTerminatorHelper, which was still causing unnecessarily slow performance on a few projects. I'm not sure if I've found the best solution to this - in particularmayAddNullTerminatorHelperlooks quite large to me, though I haven't seen it blow up in practice. Happy to take further suggestions.The change has a small positive effect on performance locally. I ran DCA on this (actually a variant with the two queries enabled) and only saw a 29s overall improvement there, which is likely not statistically significant.
@MathiasVP