[RS6000, patch] pr57936, ICE in rs6000_secondary_reload_inner

[Alan Modra]

On Tue, Feb 25, 2014 at 02:30:59PM +0100, Ulrich Weigand wrote:
> Alan Modra wrote:
> 
> > Normally, reload 2, the secondary reload for reload 3, would result in
> > a call to reload_v16qi_si_load with (reg:V16QI 78 1) as its "reg"
> > argument, and the mem home for pseudo reg 159 as its "mem" arg.
> > 
> > However, reload1.c:choose_reload_regs has code to, as the comment
> > says: 
> > 	  /* First see if this pseudo is already available as reloaded
> > 	     for a previous insn.
> > 
> > In this case reload finds such a register, so reload_v16qi_si_load
> > then sees the register as its "mem" argument, and spits the dummy.
> 
> This still seems odd to me, I don't think the intent was that the
> back-end secondary reload code is supposed to handle such cases.
> 
> Instead, there's code in emit_input_reload_insns that is supposed
> to re-check whether a secondary reload is still needed if something
> changed significantly, e.g. if a value was inherited:
> 
>   /* If we have a secondary reload, pick up the secondary register
>      and icode, if any.  If OLDEQUIV and OLD are different or
>      if this is an in-out reload, recompute whether or not we
>      still need a secondary register and what the icode should
>      be.  If we still need a secondary register and the class or
>      icode is different, go back to reloading from OLD if using
>      OLDEQUIV means that we got the wrong type of register.  We
>      cannot have different class or icode due to an in-out reload
>      because we don't make such reloads when both the input and
>      output need secondary reload registers.  */
> 
> Note the condition "if OLDEQUIV and OLD are different" should be
> true if the input value was inherited.  Can you check whether
> this case is hit with your test case?

No.  oldequiv and old are both (reg:V16QI 32 0).

reload_override_in[j] is (reg:V16QI 32 0), and rl->in_reg is
(subreg:V16QI (reg:V2DI 159 [ D.2446 ]) 0), so perhaps we're missing a
subreg test in

  if (reload_override_in[j]
      && REG_P (rl->in_reg))
    {
      oldequiv = old;
      old = rl->in_reg;
    }

I'll follow this up after getting some sleep.  Right now I'm too tired
to think straight.

Note that rs6000_secondary_reload_inner is not emitting a nop..

  c4:   39 21 00 40     addi    r9,r1,64
  c8:   38 61 00 20     addi    r3,r1,32
  cc:   7c 3c ee 99     lxvd2x  vs33,r28,r29
  d0:   7c 1f ee 98     lxvd2x  vs0,r31,r29
  d4:   38 9f 00 d0     addi    r4,r31,208
  d8:   38 a0 00 10     li      r5,16
  dc:   7c 00 4f 98     stxvd2x vs0,0,r9        (1)
  e0:   10 01 ed c4     vsld    v0,v1,v29
  e4:   f0 20 04 91     xxlor   vs33,vs0,vs0	(2)
  e8:   10 00 07 ab     vperm   v0,v0,v0,v30
  ec:   10 00 f8 00     vaddubm v0,v0,v31
  f0:   10 01 08 2b     vperm   v0,v1,v1,v0	(3)

(1) the previous reload of pseudo 159
(2) the insn emitted by rs6000_secondary_reload_inner
(3) insn 61 (v1==vs33)

-- 
Alan Modra
Australia Development Lab, IBM