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Re: AIX regression due to DFA scheduler merge
- From: law at redhat dot com
- To: David Edelsohn <dje at watson dot ibm dot com>
- Cc: Vladimir Makarov <vmakarov at redhat dot com>, gcc-patches at gcc dot gnu dot org, Mark Mitchell <mark at codesourcery dot com>
- Date: Fri, 31 May 2002 16:25:44 -0600
- Subject: Re: AIX regression due to DFA scheduler merge
- Reply-to: law at redhat dot com
In message <200205311938.PAA23884@makai.watson.ibm.com>, David Edelsohn writes:
> >>>>> Vladimir Makarov writes:
>
> Vlad> For LIBCALL1 function no_conflict_p still returns TRUE. Actually I
> Vlad> don't know what solution to choose. The both of them have advantages
> Vlad> and disadvantages:
>
> Vlad> Fix in n_conflict_p is easier and permits insn scheduling of two
> Vlad> libcalls which, with my point of view, is more important than
> Vlad> opportunity in register allocation for processors needing good insn
> Vlad> scheduling.
>
> Vlad> On the other hand, we have unclear rtx code (nested libcalls and no
> Vlad> dependencies in rtx). Checking the nested calls probably is more
> Vlad> expensive. The fix in the scheduler is better with this point of view
> .
>
> If I understand Jeff's earlier comment correctly, the local-alloc
> problem may help with the latent bugs uncovered in the proposed
> SCHED_GROUP fix. The SCHED_GROUP patch is necessary for other reasons, so
> we may need *both* fixes.
Well, initial experiments haven't shown a difference in behavior of the
sched_group_p work if I bludgeon the libcall/noconflict stuff into submission,
so fixing one isn't necessarily going to impact the other. Sigh...
jeff