Re: [PATCH] Improve overhead of tree-affine.c a bit

[Kyrill Tkachov <kyrylo dot tkachov at foss dot arm dot com>]

Hi Richard,

On 10/12/18 13:44, Richard Biener wrote:
> When working on PR63184 I noticed that tree-affine.c is still one of
> the gimple_assign_rhs_to_tree callers and does so quite aggressively
> for no good reason.  The following restricts it to the cases we
> handle in tree_to_aff_combination, axing one unreachable case.
> It also makes sure to cache expanded combinations with SSA names
> as keys rather than a GENERIC conversion tree which isn't shared
> anyways.
>
> Bootstrapped and tested on x86_64-unknown-linux-gnu, object files
> in gcc/ are the same patched/unpatched with the exception of
> tree-affine.o.
>
> Applied to trunk.
>
> Richard.
>
> 2018-12-10  Richard Biener  <rguenther@suse.de>
>
>         * tree-affine.c (tree_to_aff_combination): Remove unreachable
>         MEM_REF case.
>         (aff_combination_expand): Cache on SSA names, not possibly
>         on conversion trees.  Avoid expanding cases we do not handle.
>
> diff --git a/gcc/tree-affine.c b/gcc/tree-affine.c
> index 96b479dfc4c..41c52ab468d 100644
> --- a/gcc/tree-affine.c
> +++ b/gcc/tree-affine.c
> @@ -351,6 +351,7 @@ tree_to_aff_combination (tree expr, tree type, aff_tree *comb)
>        return;
>
>      case MEM_REF:
> +      gcc_unreachable ();
>        if (TREE_CODE (TREE_OPERAND (expr, 0)) == ADDR_EXPR)
>          tree_to_aff_combination (TREE_OPERAND (TREE_OPERAND (expr, 0), 0),
>                                   type, comb);

The code after the gcc_unreachable is now dead and can be removed?

Thanks,
Kyrill

> @@ -721,21 +722,39 @@ aff_combination_expand (aff_tree *comb ATTRIBUTE_UNUSED,
>        if (TREE_CODE_CLASS (code) == tcc_reference)
>          continue;
>
> -      if (!*cache)
> -       *cache = new hash_map<tree, name_expansion *>;
> -      name_expansion **slot = &(*cache)->get_or_insert (e);
> -      exp = *slot;
> -
> +      name_expansion **slot = NULL;
> +      if (*cache)
> +       slot = (*cache)->get (name);
> +      exp = slot ? *slot : NULL;
>        if (!exp)
>          {
> +         /* Only bother to handle cases tree_to_aff_combination will.  */
> +         switch (code)
> +           {
> +           case POINTER_PLUS_EXPR:
> +           case PLUS_EXPR:
> +           case MINUS_EXPR:
> +           case MULT_EXPR:
> +           case NEGATE_EXPR:
> +           case BIT_NOT_EXPR:
> +           CASE_CONVERT:
> +             rhs = gimple_assign_rhs_to_tree (def);
> +             break;
> +           case ADDR_EXPR:
> +           case INTEGER_CST:
> +           case POLY_INT_CST:
> +             rhs = gimple_assign_rhs1 (def);
> +             break;
> +           default:
> +             continue;
> +           }
> +         tree_to_aff_combination (rhs, TREE_TYPE (name), &current);
>            exp = XNEW (struct name_expansion);
>            exp->in_progress = 1;
> -         *slot = exp;
> -         rhs = gimple_assign_rhs_to_tree (def);
> -         if (e != name)
> -           rhs = fold_convert (type, rhs);
> -
> -         tree_to_aff_combination_expand (rhs, comb->type, &current, cache);
> +         if (!*cache)
> +           *cache = new hash_map<tree, name_expansion *>;
> +         (*cache)->put (name, exp);
> +         aff_combination_expand (&current, cache);
>            exp->expansion = current;
>            exp->in_progress = 0;
>          }
> @@ -746,6 +765,8 @@ aff_combination_expand (aff_tree *comb ATTRIBUTE_UNUSED,
>            gcc_assert (!exp->in_progress);
>            current = exp->expansion;
>          }
> +      if (!useless_type_conversion_p (comb->type, current.type))
> +       aff_combination_convert (&current, comb->type);
>
>        /* Accumulate the new terms to TO_ADD, so that we do not modify
>           COMB while traversing it; include the term -coef * E, to remove