AIX regression due to DFA scheduler merge
law@redhat.com
law@redhat.com
Fri May 31 13:57:00 GMT 2002
In message <3CF7DA0F.B8C69795@redhat.com>, Vladimir Makarov writes:
> > 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.
>
> I've just read email thread about the SCHED_GROUP patch. The idea is
> clear and its implementation should prevent the bug occurring. So I
> don't think that the local-alloc problem may help with the latent bugs
> uncovered in the proposed SCHED_GROUP fix".
>
> Also I don't think SCHED_GROUP patch is good for all processors and
> tests. It remove probability to generate a better insn schedules.
> Although there are cases (when the register pressure is too high) when
> better insn schedules result in worse code. This is standard conflict
> of separate insn scheduler and register allocator. It can be solved by
> some their integration not rejecting opportunities in one optimization.
> So I don't like the SCHED_GROUP patch (its libcall part).
>
> Although the idea not to move clobber too far is right, but it should
> be solved not by making all LIBCALL as SCHED_GROUP. At least it is
> better to make only clobber and the 1st insn used the register as a
> SCHED_GROUP.
BTW, I should also mention that I think libcall blocks suck and they should
be eliminated in the long term. But they're going to be around for a while
so we should do something sensible with them.
jeff
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