On 4/12/07, Steven Bosscher <stevenb.gcc@gmail.com> wrote:
On 4/12/07, Vladimir Makarov <vmakarov@redhat.com> wrote:
> An interesting observation is that the more hard registers the
processor
> has, the bigger slowdown is. Although it might be a coincidence.
Yes, I noticed this too. I don't believe this is a coincidence. It's
the first thing I was planning to look into, in fact.
The problem seems to have to do with how the RTL loop optimizers work.
They analyze a subcfg with df, and this is incredibly slow right now.
To give you some idea, we spend more than 35% of the total compile
time in "loop analysis" (TV_LOOP) for a fairly typical Fortran 90
program with lots of small loops, and almost all that extra time is
spent in df_reorganize_refs_by_reg.
So, Vlad, thanks for helping us identify a serious bottleneck! Kenny
said he has some ideas about how to fix this.