[dropping the bogus address I accidentally typed on the command line]
On Sat, Aug 25, 2012 at 7:08 PM, Cary Coutant <ccout...@google.com> wrote:
> This patch is for trunk and the google/gcc-4_7 branch.
>
> When a class template instantiation is moved into a separate type unit,
> it can bring along a lot of other referenced types into the type unit,
> especially if the template is derived from another (large) type that
> does not have an actually have a type definition in a type unit of its
> own. When there are many instantiations of the same template, we get
> a lot of duplication, and in the worst case (a template with several
> parameters, instantiated multiple times along each dimension), GCC
> can end up taking a long time and exhausting available memory. Because
> instantiations typically happen in .cc files, and the resulting type
> definition is unlikely to be useful as a comdat type unit, this patch
> avoids the problem by choosing not to move template instantiations
> into type units.
>
> Bootstraps and passes regression tests. Also tested with a large
> internal test case that previously resulted in out-of-memory during
> compilation.
>
> Google ref b/7041390.
>
>
> 2012-08-25 Cary Coutant <ccout...@google.com>
>
> gcc/
> * dwarf2out.c (is_template_instantiation): New function.
> (should_move_die_to_comdat): Reject types that are template
> instantiations.
>
>
> Index: gcc/dwarf2out.c
> ===================================================================
> --- gcc/dwarf2out.c (revision 190681)
> +++ gcc/dwarf2out.c (working copy)
> @@ -7277,6 +7277,21 @@ contains_subprogram_definition (dw_die_r
> return 0;
> }
>
> +/* Return non-zero if this DIE represents a template instantiation. */
> +
> +static int
> +is_template_instantiation (dw_die_ref die)
> +{
> + dw_die_ref c;
> +
> + FOR_EACH_CHILD (die, c,
> + if (c->die_tag == DW_TAG_template_type_param
> + || c->die_tag == DW_TAG_template_value_param
> + || c->die_tag == DW_TAG_GNU_template_template_param)
> + return 1);
> + return 0;
> +}
> +
> /* Return non-zero if this is a type DIE that should be moved to a
> COMDAT .debug_types section. */
>
> @@ -7294,6 +7309,7 @@ should_move_die_to_comdat (dw_die_ref di
> if (is_declaration_die (die)
> || get_AT (die, DW_AT_abstract_origin)
> || is_nested_in_subprogram (die)
> + || is_template_instantiation (die)
> || contains_subprogram_definition (die))
> return 0;
> return 1;
