Jeffrey A Law - Re: Delay branch scheduling vs. the CFG (original) (raw)

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• From: Jeffrey A Law
• To: Richard Henderson
• Cc: Steven Bosscher , gcc at gcc dot gnu dot org
• Date: Wed, 16 Nov 2005 13:24:57 -0700
• Subject: Re: Delay branch scheduling vs. the CFG
• References: <200511132120.14753.stevenb@suse.de> <1131915750.3728.348.camel@slowpoke> <200511132220.21202.stevenb@suse.de> <1131917191.3728.357.camel@slowpoke> <20051116200651.GD16133@redhat.com>
• Reply-to: law at redhat dot com

On Wed, 2005-11-16 at 12:06 -0800, Richard Henderson wrote:

On Sun, Nov 13, 2005 at 02:26:31PM -0700, Jeffrey A Law wrote:

On Sun, 2005-11-13 at 22:20 +0100, Steven Bosscher wrote:

On Sunday 13 November 2005 22:02, Jeffrey A Law wrote:

No great insights on how to make dbr_schedule CFG aware -- just remember that a filled delay slot can represent 3 different cases:

1. An extension of the block containing the sequence.

2. An extension of the block at the target of a branch.

3. An extension of the fall-thru block.

4. An entirely new basic block on its own.

When can option 4 happen?? IIRC it occurs when there was only 1 insn in either the target or fall-thru block. When it gets sucked into the delay slot of a branch, then it is effectively its own basic block.

I'd be comfortable modeling all of these as (1), with the understanding that the delay slots may be conditionally executed, as if with cond_exec. Seems clean enough to me. jeff

• References:
  • Delay branch scheduling vs. the CFG
    * From: Steven Bosscher
  • Re: Delay branch scheduling vs. the CFG
    * From: Jeffrey A Law
  • Re: Delay branch scheduling vs. the CFG
    * From: Steven Bosscher
  • Re: Delay branch scheduling vs. the CFG
    * From: Jeffrey A Law
  • Re: Delay branch scheduling vs. the CFG
    * From: Richard Henderson