Improve ivopts handling of forced scales

[Bin.Cheng]

On Fri, Nov 3, 2017 at 4:28 PM, Richard Sandiford
<richard.sandiford@linaro.org> wrote:
> This patch improves the ivopts address cost calculcation for modes
> in which an index must be scaled rather than unscaled.  Previously
> we would only try the scaled form if the unscaled form was valid.
>
> Many of the SVE tests rely on this when matching scaled indices.
>
> Tested on aarch64-linux-gnu, x86_64-linux-gnu and powerpc64-linux-gnu.
> OK to install?
OK.

Thanks,
bin
>
> Richard
>
>
> 2017-11-03  Richard Sandiford  <richard.sandiford@linaro.org>
>             Alan Hayward  <alan.hayward@arm.com>
>             David Sherwood  <david.sherwood@arm.com>
>
> gcc/
>         * tree-ssa-loop-ivopts.c (get_address_cost): Try using a
>         scaled index even if the unscaled address was invalid.
>         Don't increase the complexity of using a scale in that case.
>
> Index: gcc/tree-ssa-loop-ivopts.c
> ===================================================================
> --- gcc/tree-ssa-loop-ivopts.c  2017-11-03 12:20:07.041206480 +0000
> +++ gcc/tree-ssa-loop-ivopts.c  2017-11-03 12:20:07.193201997 +0000
> @@ -4333,18 +4333,25 @@ get_address_cost (struct ivopts_data *da
>    machine_mode addr_mode = TYPE_MODE (type);
>    machine_mode mem_mode = TYPE_MODE (TREE_TYPE (*use->op_p));
>    addr_space_t as = TYPE_ADDR_SPACE (TREE_TYPE (use->iv->base));
> +  /* Only true if ratio != 1.  */
> +  bool ok_with_ratio_p = false;
> +  bool ok_without_ratio_p = false;
>
>    if (!aff_combination_const_p (aff_inv))
>      {
>        parts.index = integer_one_node;
>        /* Addressing mode "base + index".  */
> -      if (valid_mem_ref_p (mem_mode, as, &parts))
> +      ok_without_ratio_p = valid_mem_ref_p (mem_mode, as, &parts);
> +      if (ratio != 1)
>         {
>           parts.step = wide_int_to_tree (type, ratio);
>           /* Addressing mode "base + index << scale".  */
> -         if (ratio != 1 && !valid_mem_ref_p (mem_mode, as, &parts))
> +         ok_with_ratio_p = valid_mem_ref_p (mem_mode, as, &parts);
> +         if (!ok_with_ratio_p)
>             parts.step = NULL_TREE;
> -
> +       }
> +      if (ok_with_ratio_p || ok_without_ratio_p)
> +       {
>           if (maybe_nonzero (aff_inv->offset))
>             {
>               parts.offset = wide_int_to_tree (sizetype, aff_inv->offset);
> @@ -4444,7 +4451,9 @@ get_address_cost (struct ivopts_data *da
>
>    if (parts.symbol != NULL_TREE)
>      cost.complexity += 1;
> -  if (parts.step != NULL_TREE && !integer_onep (parts.step))
> +  /* Don't increase the complexity of adding a scaled index if it's
> +     the only kind of index that the target allows.  */
> +  if (parts.step != NULL_TREE && ok_without_ratio_p)
>      cost.complexity += 1;
>    if (parts.base != NULL_TREE && parts.index != NULL_TREE)
>      cost.complexity += 1;