On Fri, Jan 1, 2021 at 10:16 PM Gary Oblock via Gcc <gcc@gcc.gnu.org> wrote:
>
> The offsets seem to actually be created. However,
> they are almost immediately are being deleted.
Use a watchpoint to see where.
> Any ideas what's going on? Has some kind
> of memory management gizmo gone awry?
>
> Gary
>
> PS For anybody who has been following my travails with the instance
> interleaving structure
> reorganization optimization, this is occurring
> with the Mcf sources from SPEC17.
>
> ________________________________
> From: Gary Oblock <g...@amperecomputing.com>
> Sent: Wednesday, December 30, 2020 11:00 PM
> To: gcc@gcc.gnu.org <gcc@gcc.gnu.org>
> Subject: A problem with field decl offsets in newly minted types
>
> I'm having some grief with creating/using some modified types.
>
> I problem occurs in tree-ssa-sccvn.c when some code tries
> to take a DECL_FIELD_OFFSET and unfortuenately gets a null
> that causes a crash.
>
> So, I traced this back the to types I created. Note, the method I used
> has seemed to be fairly robust (some other engineers in our China
> group even successfully copied it for thier own optimization.)
> However, the DECL_FIELD_OFFSET offset is definitely null for
> the fields which I created in the new versions of the types.
>
> Here is what I'm doing.
>
> tree type_prime = lang_hooks.types.make_type (RECORD_TYPE);
>
> const char *base_type_name =
> identifier_to_locale ( IDENTIFIER_POINTER ( TYPE_NAME ( type)));
> size_t len = strlen ( MY_PREFIX) + strlen ( base_type_name);
> char *rec_name = ( char*)alloca ( len + 1);
> strcpy ( rec_name, MY_PREFIX);
> strcat ( rec_name, base_type_name);
>
> TYPE_NAME ( reorg_type_prime) = get_identifier ( rec_name);
>
> tree field;
> tree new_fields = NULL;
> for ( field = TYPE_FIELDS ( type); field; field = DECL_CHAIN ( field))
> {
> // Probably useful in creating the new field type.
> tree old_fld_type = TREE_TYPE ( field);
>
> // Whatever you want the new field type to be
> tree new_fld_type = ...;
> tree new_decl =
> build_decl ( DECL_SOURCE_LOCATION (field),
> FIELD_DECL, DECL_NAME (field), new_fld_type);
> DECL_CONTEXT ( new_decl) = type_prime;
> layout_decl ( new_decl, 0);
> DECL_CHAIN ( new_decl) = new_fields;
> new_fields = new_decl;
> }
>
> TYPE_FIELDS ( type_prime) = nreverse ( new_fields);
> layout_type ( type_prime);
>
> Note, when I change any declaration to have a modified type
> I run relayout_decl on them.
>
> If somebody could please tell what bit I'm missing or what I'm doing
> wrong I'd really appreciate it. Looking at the code in layout_type,
> it should be setting the decl field offsets with place_field and I
> don't have a clue what's going on.
>
> Thanks,
>
> Gary
>
>
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