C6X port 4/11: Backtracking scheduler

[Bernd Schmidt]

On 05/11/2011 10:04 AM, Richard Sandiford wrote:
> Neat!  It'll be interesting to see how easy it would be to convert
> recog and in-tree delayed-branch targets to use this form instead of
> SEQUENCEs.  It'd certainly be a big step towards keeping the CFG
> around during and after md-reorg.  I might look at that (getting
> rid of SEQUENCEs in the insn stream) "if I have time".  But...
> 
> ...your message and examples all seem to emphasis unconditional jumps.
> How good a job does the scheduler do for conditional jumps?  E.g. do we
> steal from the branch target in cases where that's useful?

It uses sched-ebb, which means it sort of does a reasonable job, but
it's weaker than reorg.c in some respects. I'd like to turn sched-ebb
into sched-dag and add better support for predicating insns when moving
them across a branch (there's some code for it in c6x.c), but that'll
need more work.


Bernd