[Bug target/104686] [12 Regression] Huge compile-time regression building SPEC 2017 538.imagick_r with -march=skylake

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104686

--- Comment #21 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Richard Biener <rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:8fede2876a751d53a28442dcca32466daa929daa

commit r12-7451-g8fede2876a751d53a28442dcca32466daa929daa
Author: Richard Biener <rguenther@suse.de>
Date:   Wed Mar 2 08:55:58 2022 +0100

    rtl-optimization/104686 - speedup IRA allocno conflict test

    In this PR allocnos_conflict_p takes 90% of the compile-time via
    the calls from update_conflict_hard_regno_costs.  This is due to
    the high number of conflicts recorded in the dense bitvector
    representation.  Fortunately we can take advantage of the bitvector
    representation here and turn the O(n) conflict test into an O(1) one,
    greatly speeding up the compile of the testcase from 39s to just 4s
    (93% IRA time to 26% IRA time).

    While for the testcase in question the first allocno is almost always
    the nice one the patch tries a more systematic approach to finding
    the allocno to iterate object conflicts over.  That does reduce
    the actual number of compares for the testcase but it doesn't make
    a measurable difference wall-clock wise.  That's not guaranteed
    though I think so I've kept this systematic way of choosing the
    cheapest allocno.

    2022-03-02  Richard Biener  <rguenther@suse.de>

            PR rtl-optimization/104686
            * ira-color.cc (object_conflicts_with_allocno_p): New function
            using a bitvector test instead of iterating when possible.
            (allocnos_conflict_p): Choose the best allocno to iterate over
            object conflicts.
            (update_conflict_hard_regno_costs): Do allocnos_conflict_p test
            last.