This is the mail archive of the
mailing list for the GCC project.
Re: two dfa problems
On Sun, May 05, 2002 at 01:45:31PM -0400, Vladimir N. Makarov wrote:
> Richard, I'll look at this problem tomorrow. But I think your estimation is
> not accurate.
Correct. I later determined that the effect was caused by the
reservation problem that you diagnosed. Indeed, your analysis
> [...] It means that we can issue infinite number of such insns.
suggests the reason for this failure.
> To prevent this we should put ev5_e1 and ev5_e0 in the same automaton.
I have done this in my current patch.
> If such solution were not acceptable, we could remove occurrence
> of ev5_fa from fdiv reservations nearby the end of the long reservations.
I have also done this in my current patch. You're right -- modeling
the late reservation is silly. Especially since the divide instruction
has a data-dependent latency.
> Because It is easy to miss such problem, I've made a patch which generates
> error (and reports the units) if the units should be in the same automaton.
Thanks for looking at this.