Michal Jires <mji...@suse.cz> writes: > On Thu, 2025-03-27 at 15:33:44 +0000, Sam James wrote: >> >> One thing I wasn't quite sure on yet: is -flto-partition=cache automatic >> with -flto-incremental? Or is it just an optional flag I can pass for >> more effective incremental LTO? >> >> If it's the latter, should we mention that in the -flto-incremental >> documentation? >> > > It is not automatic, because different partitioning will result in > different executable. Most of the time this should not matter, but for > example a performance bug depending on instruction alignment would not > be reproduced.
Thanks! That makes sense. > > The cache partitioning is most useful with large amount of divergences > per diverging partition. Which was very useful at the start, but it > happens less with each divergence I remove. > Last time I measured it, the improvement was no longer noticeable > without debug symbols and only a few percent improvement with debug > symbols, with one outlier case being ~50 % worse. > > The benefits are minor, a bit unclear, and caveats are hard to properly > explain. So I do not want to actively recommend the option for now. ACK. Appreciate the explanation. > [...] sam
