From: Alex Turjan <aturjan@yahoo.com>
To: gcc@gcc.gnu.org, "Amker.Cheng" <amker.cheng@gmail.com>
Subject: Re: Question about the difference between two instruction scheduling passes
Date: Wed, 19 Aug 2009 23:47:00 -0000 [thread overview]
Message-ID: <490580.44033.qm@web62402.mail.re1.yahoo.com> (raw)
In-Reply-To: <e8b251c80908190744q56bfaac1k11561d52f2a381a1@mail.gmail.com>
> 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?
Regardless of the target architecture from the correctness point of view sched1 can be disabled. sched1 has as purpose shortening live ranges.
Short live ranges allow the register allocation to:
1. generate less spills and
2. also to avoid useless live ranges splitting.
The second point impacts the register renaming phase which allows sched2 phase to extract more ilp.
prev parent reply other threads:[~2009-08-19 20:30 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
2009-08-19 23:47 ` Alex Turjan [this message]
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