Scheduler questions (related to PR17808)

[Dale Johannesen]

On Jun 29, 2005, at 3:46 PM, Steven Bosscher wrote:
> I have a question about the scheduler.  Forgive me if I'm totally
> missing the point here, this scheduling business is not my thing ;-)
>
> Consider the following snippet that I've derived from PR17808 with a
> few hacks in the compiler to renumber insns and dump RTL with all the
> dependencies before scheduling.  There is a predicate register that
> gets set, then a few cond_exec insns, then a jump, and finally a set
> using some of the registers that may be set by the cond_exec insns.
> This is the RTL before scheduling:
>
> <snip>

> Notice how the conditional sets of r14 and r17 in insns 9 and 10 have
> been moved past insn 14, which uses these registers.  Shouldn't there
> be true dependencies on insns 9 and 10 for insn 14?

I think so.  This is figured out in sched_analyze_insn in sched-deps.c, 
I'd
suggest stepping through there.