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Differential D55557

param: Refactor rounddown
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Authored by aokblast on Fri, Feb 27, 7:17 AM.
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imp
markj
jhb
Summary

Obviously, a minus + reminder is faster than divide and multiply in most of the platform.

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rG FreeBSD src repository
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Buildable 71063
Build 67946: arc lint + arc unit

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aokblast created this revision.Fri, Feb 27, 7:17 AM
Herald added a subscriber: imp. · View Herald TranscriptFri, Feb 27, 7:17 AM
aokblast requested review of this revision.Fri, Feb 27, 7:17 AM
Harbormaster completed remote builds in B71063: Diff 172848.Fri, Feb 27, 7:17 AM
aokblast edited the summary of this revision. (Show Details)Fri, Feb 27, 7:17 AM
aokblast added reviewers: imp, markj, jhb.
markj added a comment.Fri, Feb 27, 3:15 PM

Does it actually make a difference in generated code? I would expect a compiler to be able to do this transformation.

aokblast abandoned this revision.Fri, Feb 27, 3:33 PM

I did some experiment and you are right, the compiler optimize it above O1.
Also, my assumption is wrong since reminder in aarch64 actually convert into udiv + msub, which is not faster than what we previous have.
Thanks!

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sys/sys/_param.h

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