Re: TMSC320C6x port: return label is being deleted

[Adrian Strätling<adrian dot straetling at cs dot tu-chemnitz dot de>]

Graham Stott wrote:

> Hi,
>
> --- Adrian Strätling <adrian.straetling@cs.tu-chemnitz.de> wrote: 
>  
>
> > can I somehow attach the label to the call insn, so that the output 
> > function can get the label number and print it?
> >    
> Not you are looking at it from the wrong angle.
>
>  
>
> > I tried:
> > "
> > insn = gen_rtx_CALL (VOIDmode, mem, const0_rtx);
> > emit_call_insn(insn);
> > emit_label(ret_label);
> > REG_NOTES (insn) = gen_rtx_INSN_LIST (REG_LABEL, ret_label, 
> > REG_NOTES(insn));
> > LABEL_NUSES(ret_label)++;
> > "
> >    
> You don't need/want all the stuff after after your emit_call_insn
>
>  
>
> > which results in RTL:
> > "
> > (insn 17 15 18 2 (set (mem:SI (pre_dec:SI (reg/f:SI 47 b15)) [0 S4 A32])
> >        (label_ref:SI 19)) -1 (nil)
> >    (insn_list:REG_LABEL 19 (nil)))
> >
> > (call_insn 18 17 19 2 (call (mem:QI (symbol_ref:SI ("nop") [flags 0x3] 
> > <function_decl 0x401d45e4 nop>) [0 S1 A8])
> >        (const_int 0 [0x0])) -1 (nil)
> >    (expr_list:REG_EH_REGION (const_int 0 [0x0])
> >        (nil))
> >    (nil))
> >
> > (code_label 19 18 34 3 5 "" [1 uses])
> > "
> >
> > It seems I have to emit the label to get the REFs right.
> > However, I miss the the "REG_LABEL  19" in the insn list of the call insn.
> >
> > Another approach would be to walk the dependency list at the time of 
> > output, but I'd rather prefer the first one.
> >    
> No you are making life hard for yourself it;s much easier that you think
> do it all in your define_insn for the call.
>
> In your define_insn for your call you use something like.
> (define_insn "..."
>  []
>  ""
> {
>  rtx label = gen_label_rtx ();
>
>  output your call sequence
>  ..
>
>  now output the label
>  
>  return "";
> }
>
> See how the rest of the compiler doesn't know or care
> about these labels.
>
>  
Thanks.
This is a solution for the problem, but I'd really like to find a better 
(faster) one.
Pleas, let me explain why I do not really want to do it that way. :)

This call sequence would look like:
  mvkl   L5   a0      ; move low part of return address
|| mvkl   foo  b0      ; move low part of function address
  mvkh   L5   a0      ; move high part of return address
|| mvkh   foo  b0      ; move high part of function address
  b      b0           ; call function
  stw    a0   *--b15  ; push return address onto stack (delay slot 1)
  nop    4            ; delay slots 2 - 5  (banch has 5)
L5:

This is the shortest sequence I can momentarily think of (6 insns, 8 
cycles).
The architecture theoretically supports 8 parallel insns (||) per cycle 
(that makes 64 possible instructions instead of the 6). If all 
instructions are separate rtl insn, the scheduler can group them in a 
way so that more than one task can be done simultaneously, though of 
course there are a lot of constraints.

If I follow my previous thoughts, I need a way to tag information to 
particular insns, preferably a buit-in one.

I would also like passing some scheduling details and I guessed I could 
do that similarly. For instance: The cpu_unit the scheduler assigns to 
each insn should appear in the output. If that would not be possible, I 
had to recalculate this units myself, as the assembler I wrote does not 
do that either.
A possible solution would be to build up a private data structure of 
some kind to connect the needed info to the UID of the insn, but I would 
prefer an easier way.

Thanks for your patience ;-)

greets,
Adrian