https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69564
Jeffrey A. Law <law at redhat dot com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |law at redhat dot com --- Comment #26 from Jeffrey A. Law <law at redhat dot com> --- In response to c#24. Coalescing's primary sort key is highly dependent on the edge frequencies -- which is generally what we want. The highest edge frequency represents the highest cost for any particular copy implied by a PHI node. This obviously falls down if there are > 1 lower frequency copies that can't be coalesced due to a higher frequency copy that does coalesce and the sum of the lower frequency copy costs are greater than the sum of the single higher frequency copy. One might be able to model that by looking at the conflict lists, but before going down that path, it'd obviously be best to know if that scenario is the root cause of the slowdown.