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 <rgue...@gcc.gnu.org>: https://gcc.gnu.org/g:8fede2876a751d53a28442dcca32466daa929daa commit r12-7451-g8fede2876a751d53a28442dcca32466daa929daa Author: Richard Biener <rguent...@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 <rguent...@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.
