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Re: (RFA): Enable first scheduling pass for SH4
- From: "Vladimir N. Makarov" <vmakarov at redhat dot com>
- To: "Sanjiv Kumar Gupta, Noida" <sanjivg at noida dot hcltech dot com>
- Cc: Richard Henderson <rth at redhat dot com>, gcc-patches at gcc dot gnu dot org,Joern Rennecke <joern dot rennecke at superh dot com>,"Naveen Sharma, Noida" <naveens at noida dot hcltech dot com>
- Date: Fri, 05 Sep 2003 10:45:42 -0400
- Subject: Re: (RFA): Enable first scheduling pass for SH4
- References: <E04CF3F88ACBD5119EFE00508BBB21210BC90572@EXCH-01>
"Sanjiv Kumar Gupta, Noida" wrote:
> > On Wed, Sep 03, 2003 at 01:56:26PM +0530, Sanjiv Kumar Gupta,
> > Noida wrote:
> > > The overall idea is to keep count of SImode and SFmode regs
> > required by
> > > already scheduled insns.
> >
> > I don't think this should at all be done via magic hooks in
> > the sh backend.
>
> The heuristics are pretty target specific. Do you think,
> I should change the generic scheduler for this?
>
I think Richard is right. You could make it more general (register
pressure calculation and reordering ready queue) because it could be
profitable for other ports (like arm or sparc) too. Then the most of
code could be in the scheduler itself. And may be one hook to switch on
(off) the heuristic for ports which could have benefit from this
heuristic. If there is no harm from this for all ports, the hook could
be removed.
Another question, I see results only with and without the 1st insn
scheduling. They are impressive. But having results with and without
register pressure heuristics is more appropriate (may be they will be
more impressive). It is also interesting to look at the SPEC (95 or
2000) results too. I saw many times when small benchmarks (with few
loops) got the performance improvement but SPEC benchmarks (like gcc)
got the degradation. If it is not possible that is ok (unfortunately
many people have no access to SPEC).
Vlad