Re: Reserving a number of consecutive registers

[fearyourself <fearyourself at gmail dot com>]

Ok, I've move forward in this problem by identifying the loads I want
to suggest hard registers for and I've inspired myself with code in
combine_regs and finally have tried this:

      /* Suggest pseudo register to hard register */
      s_qtyno=reg_qty[pseudo];

      if (s_qtyno >= 0) {
          if (qty_phys_copy_sugg[s_qtyno] != 0)
          {
              SET_HARD_REG_BIT(qty_phys_copy_sugg[s_qtyno], hard);
              qty_phys_num_copy_sugg[s_qtyno]++;
          }
          else
              if (qty_phys_sugg[s_qtyno] != 0)
              {
                  SET_HARD_REG_BIT(qty_phys_sugg[s_qtyno], hard);
                  qty_phys_num_sugg[s_qtyno]++;
              }
      }

It seems that this works for most cases but there are still cases
where this does not work (I of course first test if the register hard
is free).

This is a little bit simpler than what you find in find_free_reg. Any
comments/suggestions at this point?

Thanks a lot,
Jc

On Fri, Apr 17, 2009 at 2:50 PM, fearyourself <fearyourself@gmail.com> wrote:
> Hi all,
>
> My target architecture has an load multiple instruction requiring a
> certain number of consecutive registers. I've been working on handling
> this case and trying to convince the local register allocator that he
> really does want to try to get those consecutive registers for the
> loads. But have been running into certain difficulties.
>
> For example:
>
> a = tab[0];
> b = tab[1];
> c = tab[2];
> d = tab[3];
> e = tab[4];
>
> sum = a + b + c + d + e;
>
> I would like to get :
>
> load_multiple tab, r10-r14
>
> and then have r10 linked to a, r11 to b, etc.
>
> Basically, I've worked in the direction of detecting a number of loads
> in the block from the same base register or symbol reference. I've got
> that detection running and I know in what order I want to associate
> the pseudo registers to the hard registers but I can't seem to request
> hard registers at that point. I thought I could be playing with the
> arrays qty_phys_sugg and qty_phys_copy_sugg but I have trouble
> wrapping my mind around what they really represent and how to do that.
>
> Do you have any ideas about how I can achieve this, am I going in the
> wrong direction?
>
> Thanks a lot,
> Jc
>