On Wed, 7 Mar 2012, Andrey Belevantsev wrote:
> This PR is again about insns that are recog'ed as >=0 but do not change the
> processor state. As explained in
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52203#c8, I've tried experimenting
> with an attribute marking those "empty" insns in MD files and asserting that
> all other insns do have reservations. As this doesn't seem to be interesting,
> I give up with the idea, and the below patch makes sel-sched do exactly what
> the Haifa scheduler does, i.e. do not count such insns against issue_rate when
> modelling clock cycles.
> Tested on ia64 and x86-64, OK for trunk? No testcase again because of the
> amount of flags needed.
> 2012-03-07 Andrey Belevantsev <a...@ispras.ru>
> PR rtl-optimization/52203
> * sel-sched.c (estimate_insn_cost): New parameter pempty. Adjust
> all callers to pass NULL except ...
> (reset_sched_cycles_in_current_ebb): ... here, save the value
> in new variable 'empty'. Increase issue_rate only for
> non-empty insns.
This is OK.