Re: [PATCH] middle-end/114579 - speed up add_scope_conflicts

[Jeff Law <jeffreyalaw@gmail.com>]

On 4/4/24 6:41 AM, Richard Biener wrote:
> The following speeds up stack variable conflict detection by recognizing
> that the all-to-all conflict recording is only necessary for CFG merges
> as it's the unioning of the live variable sets that doesn't come with
> explicit mentions we record conflicts for.
> 
> If we employ this optimization we have to make sure to perform the
> all-to-all conflict recording for all CFG merges even those into
> empty blocks where we might previously have skipped this.
> 
> I have reworded the comment before the all-to-all conflict recording
> since it seemed to be confusing and missing the point - but maybe I
> am also missing something here.
> 
> Nevertheless for the testcase in the PR the compile-time spend in
> add_scope_conflicts at -O1 drops from previously 67s (39%) to 10s (9%).
> 
> Bootstrapped and tested on x86_64-unknown-linux-gnu, OK for trunk?
> 
> Thanks,
> Richard.
> 
> 	PR middle-end/114579
> 	* cfgexpand.cc (add_scope_conflicts_1): Record all-to-all
> 	conflicts only when there's a CFG merge but for all CFG merges.
OK.  Your call on whether or not to include in gcc-14 or wait for gcc-15.

jeff