Re: [gfortran] patch for pr 21130 - 38822 lines of Fortran 90 takes more than 10 minutes to compile on a dual 3GHz P4 Linux box with lots of RAM

[Paul Thomas <paulthomas2 at wanadoo dot fr>]

Bud,

> changelog and patch attached.
>
>  
OK for trunk and 4.1.

That's brilliant!  I can only say that I am a bit ashamed of the time 
that I spent looking at that bit of code without realising that there is 
such a time penalty involved.  I have just a couple of minor points on 
the patch.

Thanks

Paul

> ------------------------------------------------------------------------
>
> Index: gcc/gcc/fortran/module.c
> ===================================================================
> --- gcc/gcc/fortran/module.c	(revision 112482)
> +++ gcc/gcc/fortran/module.c	(working copy)
> @@ -3052,26 +3052,27 @@
> }
>
> /* Recursive function to traverse the pointer_info tree and load a
> -   needed symbol.  We return nonzero if we load a symbol and stop the
> -   traversal, because the act of loading can alter the tree.  */
> +   needed symbol. Because the act of loading can alter the tree, we
> +   keep a count of all possible symbols to deal with.  */
>  
Because the act of loading can alter the tree, we return the number of 
loads that were made.

> -static int
> -load_needed (pointer_info * p)
> +static void
> +load_needed (pointer_info * p, int * symbols_remaining)
>  
Shouldn't this be symbols_loaded, rather than symbols remaining??

> {
>   gfc_namespace *ns;
>   pointer_info *q;
>   gfc_symbol *sym;
>
>   if (p == NULL)
> -    return 0;
> -  if (load_needed (p->left))
> -    return 1;
> -  if (load_needed (p->right))
> -    return 1;
> +    return ;
>
> +  load_needed (p->left, symbols_remaining);
> +  load_needed (p->right, symbols_remaining);
> +
>   if (p->type != P_SYMBOL || p->u.rsym.state != NEEDED)
> -    return 0;
> +    return ;
>
> +  (*symbols_remaining)++;
> +
>   p->u.rsym.state = USED;
>
>   set_module_locus (&p->u.rsym.where);
> @@ -3101,7 +3102,7 @@
>   mio_symbol (sym);
>   sym->attr.use_assoc = 1;
>
> -  return 1;
> +  return ;
> }
>
>
> @@ -3155,6 +3156,7 @@
>   gfc_use_rename *u;
>   gfc_symtree *st;
>   gfc_symbol *sym;
> +  int symbols_remaining;
>
>   get_module_locus (&operator_interfaces);	/* Skip these for now */
>   skip_list ();
> @@ -3323,7 +3325,12 @@
>      been loaded yet.  If one symbol requires another, the other gets
>      marked as NEEDED if its previous state was UNUSED.  */
>  
Thus, we keep on traversing the tree until no more symbols are loaded.

> -  while (load_needed (pi_root));
> +  do 
> +    { 
> +       symbols_remaining = 0;
> +       load_needed (pi_root, &symbols_remaining);
> +    }
> +  while (symbols_remaining > 0);
>
>   /* Make sure all elements of the rename-list were found in the
>      module.  */
>