From: Ian Lance Taylor <iant@google.com>
To: "Amker.Cheng" <amker.cheng@gmail.com>
Cc: gcc@gcc.gnu.org
Subject: Re: Question about the difference between two instruction scheduling passes
Date: Wed, 19 Aug 2009 23:26:00 -0000 [thread overview]
Message-ID: <m3r5v7alim.fsf@google.com> (raw)
In-Reply-To: <e8b251c80908190744q56bfaac1k11561d52f2a381a1@mail.gmail.com> (Amker Cheng's message of "Wed\, 19 Aug 2009 22\:44\:22 +0800")
"Amker.Cheng" <amker.cheng@gmail.com> writes:
> I'm currently studying implementation of instruction sched in gcc.
>
> it is possible to schedule insns directly from queue in case
> there is nothing better to do and there are still vacant dispatch slots
> in the current cycle.
>
> Gcc only does this work in the second pass, but what's the point?
> Is it wrong or just not necessary in the first sched pass?
The first scheduling pass runs before register allocation and reload so
it's going to get generally trashed anyhow. There no point to being
very precise in the first pass, it's just a rough approximation.
Ian
next prev parent reply other threads:[~2009-08-19 15:09 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-08-19 22:51 Amker.Cheng
2009-08-19 23:26 ` Ian Lance Taylor [this message]
2009-08-19 23:47 ` Alex Turjan
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