On 04/04/2017 09:00 AM, Richard Biener wrote:

> tree
> add_builtin_type (const char *name, tree type)
> {
>   tree   id = get_identifier (name);
>   tree decl = build_decl (BUILTINS_LOCATION, TYPE_DECL, id, type);
>   return lang_hooks.decls.pushdecl (decl);
> }
>
> this seems to miss setting TYPE_NAME (type) = decl - oh, that may be
> what set_underlying_type does via the langhook.

Correct, via the langhook.  I wonder if the smacking of the 
incoming-type's TYPE_NAME is so that the global tree node references the 
now-named builtin type.  If we were to make a clone here, (things like) 
VS4SI_type_node would remain an unnamed type.  And I guess debug would 
be unhappy?

> At this point I'd rather restrict fiddling in this fragile area in
> rs6000.c only ;)

me too.

> Does removing the TYPE_NAME setting fix things?

no,  those TYPE_NAME assignments are redundant -- set_underlying_type 
has already initialized it.

The attached PoC fixes 79905 (no idea what ppc test it might break)

nathan

-- 
Nathan Sidwell