Re: Delay branch scheduling vs. the CFG

[Richard Henderson <rth at redhat dot com>]

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.


r~