[Bug c/12245] [4.2/4.3/4.4 regression] Uses lots of memory when compiling large initialized arrays

[rguenther at suse dot de]

------- Comment #43 from rguenther at suse dot de  2009-02-22 19:03 -------
Subject: Re:  [4.2/4.3/4.4 regression] Uses lots of memory when
 compiling large initialized arrays

On Sun, 22 Feb 2009, hubicka at gcc dot gnu dot org wrote:

> Actual representation of constructor don't seem to be major problem here.
> 
> We seem to build _a lot_ (117MB) of CONVERT exprs just to call fold on it and
> convert integer to proper type, so counting in INTEGER_CSTs should be just
> slightly less than half of memory needed.  This seems quite silly.
> 
> The patch to not use HOST_WIDE_INT or similar for counting should save another
> 70MB of garbage (and speed up compilation), so perhaps you could dig it out?
> :))
> 
> Following patch:
> Index: convert.c
> ===================================================================
> --- convert.c   (revision 144352)
> +++ convert.c   (working copy)
> @@ -749,6 +749,11 @@ convert_to_integer (tree type, tree expr
>           break;
>         }
> 
> +      /* When parsing long initializers, we might end up with a lot of casts.
> +         Shortcut this.  */
> +      if (TREE_CODE (expr) == INTEGER_CST)
> +       return fold_unary (CONVERT_EXPR, type, expr);

fold_convert ().  But maybe not valid to do here for C std reasons, who 
knows.

> +
>        return build1 (CONVERT_EXPR, type, expr);

And probably just generally using fold_convert () would be ok as well.
Maybe they are there to make sure to build rvalues.

>      case REAL_TYPE:
> 
> Cuts gabrage production in half:
> c-typeck.c:6472 (output_init_element)                     0: 0.0%  
> 47910400:100.0%   45541112:23.7%   26342936:99.5%         19
> ggc-common.c:187 (ggc_calloc)                      67094608:46.1%          0:
> 0.0%   67162736:34.9%       1088: 0.0%         58
> tree.c:1004 (build_int_cst_wide)                   78264768:53.8%          0:
> 0.0%   78266496:40.7%          0: 0.0%    3261068
> Total                                             145570627         47910416   
>     192171521         26481588          3275033
> source location                                     Garbage            Freed   
>          Leak         Overhead            Times
> 


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12245