Re: Free more of type decls

[Richard Biener <richard dot guenther at gmail dot com>]

On Fri, Oct 26, 2018 at 9:12 AM Jan Hubicka <hubicka@ucw.cz> wrote:
>
> Hi,
> this patch frees TYPE_DECL and alignment from TYPE_DECL and also preserves
> only those TYPE_DECL pointers that are actually used to build ODR type tree.
>
> It reduces number of TYPE_DECLs streamed from WPA to ltrans to about 20%
> and is important for the patch turning types to incomplete types.  Without
> this change the TREE_TYPE of TYPE_DECL would still point back to complete type
> and duplicating TYPE_DECLs as well is somewhat laborious.

So the following is the really important hunk, correct?

> @@ -5174,7 +5174,7 @@ free_lang_data_in_type (tree type)
>
>    /* Drop TYPE_DECLs in TYPE_NAME in favor of the identifier in the
>       TYPE_DECL if the type doesn't have linkage.  */
> -  if (! type_with_linkage_p (type))
> +  if (type != TYPE_MAIN_VARIANT (type) || ! type_with_linkage_p (type))
>      {
>        TYPE_NAME (type) = TYPE_IDENTIFIER (type);
>        TYPE_STUB_DECL (type) = NULL;

Can you explain why you "free" alignment of TYPE_DECLs?  It's just some
bits...  does the FE somehow re-use those for sth else?  I wouldn't have
expected those to be set to anything meaningful.

I'm not too comfortable with setting TREE_TYPE of a TYPE_DECL to NULL.
Can we instead use void_type_node?  The tree-inline.c hunk should
probably test whether DECL_ORIGINAL_TYPE is non-null instead.

Richard.

> Bootstrapped/regtested x86_64-linux, OK?
>
> Honza
>
>         * tree-inline.c (remap_decl): Be ready that TREE_TYPE of TYPE_DECL
>         may be NULL.
>         * tree-pretty-print.c (dump_generic_node): Likewise.
>         * tree.c (free_lang_data_in_type): Free more type decls.
>         (free_lang_data_in_decl): Free type and alignment of TYPE_DECL.
> Index: tree-inline.c
> ===================================================================
> --- tree-inline.c       (revision 265492)
> +++ tree-inline.c       (working copy)
> @@ -382,7 +382,7 @@ remap_decl (tree decl, copy_body_data *i
>           /* Preserve the invariant that DECL_ORIGINAL_TYPE != TREE_TYPE,
>              which is enforced in gen_typedef_die when DECL_ABSTRACT_ORIGIN
>              is not set on the TYPE_DECL, for example in LTO mode.  */
> -         if (DECL_ORIGINAL_TYPE (t) == TREE_TYPE (t))
> +         if (TREE_TYPE (t) && DECL_ORIGINAL_TYPE (t) == TREE_TYPE (t))
>             {
>               tree x = build_variant_type_copy (TREE_TYPE (t));
>               TYPE_STUB_DECL (x) = TYPE_STUB_DECL (TREE_TYPE (t));
> Index: tree-pretty-print.c
> ===================================================================
> --- tree-pretty-print.c (revision 265492)
> +++ tree-pretty-print.c (working copy)
> @@ -1896,7 +1896,7 @@ dump_generic_node (pretty_printer *pp, t
>         }
>        if (DECL_NAME (node))
>         dump_decl_name (pp, node, flags);
> -      else if (TYPE_NAME (TREE_TYPE (node)) != node)
> +      else if (TREE_TYPE (node) && TYPE_NAME (TREE_TYPE (node)) != node)
>         {
>           pp_string (pp, (TREE_CODE (TREE_TYPE (node)) == UNION_TYPE
>                           ? "union" : "struct "));
> Index: tree.c
> ===================================================================
> --- tree.c      (revision 265492)
> +++ tree.c      (working copy)
> @@ -5174,7 +5174,7 @@ free_lang_data_in_type (tree type)
>
>    /* Drop TYPE_DECLs in TYPE_NAME in favor of the identifier in the
>       TYPE_DECL if the type doesn't have linkage.  */
> -  if (! type_with_linkage_p (type))
> +  if (type != TYPE_MAIN_VARIANT (type) || ! type_with_linkage_p (type))
>      {
>        TYPE_NAME (type) = TYPE_IDENTIFIER (type);
>        TYPE_STUB_DECL (type) = NULL;
> @@ -5354,6 +5354,8 @@ free_lang_data_in_decl (tree decl)
>        DECL_VISIBILITY_SPECIFIED (decl) = 0;
>        DECL_INITIAL (decl) = NULL_TREE;
>        DECL_ORIGINAL_TYPE (decl) = NULL_TREE;
> +      TREE_TYPE (decl) = NULL_TREE;
> +      SET_DECL_ALIGN (decl, 0);
>      }
>    else if (TREE_CODE (decl) == FIELD_DECL)
>      DECL_INITIAL (decl) = NULL_TREE;