Re: sched2, ret, use, and VLIW bundling

[Maxim Kuvyrkov <maxim at codesourcery dot com>]

DJ Delorie wrote:
> I'm working on a VLIW coprocessor for MeP.  One thing I noticed is
> that sched2 won't bundle the function's RET with the insn that sets
> the return value register, apparently because there's an intervening
> USE of that register (insn 30 in the example below).
>
> Is there any way around this?  The return value obviously isn't
> actually used there, nor does the return insn need it - that USE is
> just to keep the return value live until the function exits.

The problem may be in the dependency cost between the SET (insn 27) and 
the USE (insn 30) being >= 1.  Have you tried using 
targetm.sched.adjust_cost() hook to set the cost of USE to 0?

Anyway, this seems strange, the scheduler should just output the USEs as 
soon as they are ready.  One of the few places this can be forced untrue 
is targetm.sched.dfa_new_cycle() hook; does your port define it?

--
Maxim