On Thu, 30 Jan 2020, Jakub Jelinek wrote:
> Hi!
>
> This is something that has been discussed already a few months ago, but
> seems to have stalled. Here is Paul's patch from the PR except for the
> TREE_STATIC hunk which is wrong, and does the most conservative fn spec
> tweak for the problematic two builtins we are aware of (to repeat what is in
> the PR, both .wR and .ww are wrong for these builtins that transform one
> layout of an descriptor to another one; while the first pointer is properly
> marked that we only store to what it points to, from the second pointer
> we copy and reshuffle the content and store into the first one; if there
> wouldn't be any pointers, ".wr" would be just fine, but as there is a
> pointer and that pointer is copied to the area pointed by first argument,
> the pointer effectively leaks that way, so we e.g. can't optimize stores
> into what the data pointer in the descriptor points to). I haven't
> analyzed other fn spec attributes in the FE, but think it is better to
> fix at least this one we have analyzed.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
Thanks,
Richard.
> 2020-01-30 Paul Thomas <pa...@gcc.gnu.org>
> Jakub Jelinek <ja...@redhat.com>
>
> PR fortran/92123
> * trans-decl.c (gfc_get_symbol_decl): Call gfc_defer_symbol_init for
> CFI descs.
> (gfc_build_builtin_function_decls): Use ".w." instead of ".ww" or ".wR"
> for gfor_fndecl_{cfi_to_gfc,gfc_to_cfi}.
> (convert_CFI_desc): Handle references to CFI descriptors.
>
> --- gcc/fortran/trans-decl.c.jj 2020-01-12 11:54:36.600410587 +0100
> +++ gcc/fortran/trans-decl.c 2020-01-29 10:54:36.771077452 +0100
> @@ -1552,6 +1552,9 @@ gfc_get_symbol_decl (gfc_symbol * sym)
> sym->ts.u.cl->backend_decl = build_fold_indirect_ref
> (sym->ts.u.cl->backend_decl);
> }
>
> + if (is_CFI_desc (sym, NULL))
> + gfc_defer_symbol_init (sym);
> +
> fun_or_res = byref && (sym->attr.result
> || (sym->attr.function && sym->ts.deferred));
> if ((sym->attr.dummy && ! sym->attr.function) || fun_or_res)
> @@ -3763,12 +3766,17 @@ gfc_build_builtin_function_decls (void)
> get_identifier (PREFIX("internal_unpack")), ".wR",
> void_type_node, 2, pvoid_type_node, pvoid_type_node);
>
> + /* These two builtins write into what the first argument points to and
> + read from what the second argument points to, but we can't use R
> + for that, because the directly pointed structure contains a pointer
> + which is copied into the descriptor pointed by the first argument,
> + effectively escaping that way. See PR92123. */
> gfor_fndecl_cfi_to_gfc = gfc_build_library_function_decl_with_spec (
> - get_identifier (PREFIX("cfi_desc_to_gfc_desc")), ".ww",
> + get_identifier (PREFIX("cfi_desc_to_gfc_desc")), ".w.",
> void_type_node, 2, pvoid_type_node, ppvoid_type_node);
>
> gfor_fndecl_gfc_to_cfi = gfc_build_library_function_decl_with_spec (
> - get_identifier (PREFIX("gfc_desc_to_cfi_desc")), ".wR",
> + get_identifier (PREFIX("gfc_desc_to_cfi_desc")), ".w.",
> void_type_node, 2, ppvoid_type_node, pvoid_type_node);
>
> gfor_fndecl_associated = gfc_build_library_function_decl_with_spec (
> @@ -4398,6 +4406,8 @@ convert_CFI_desc (gfc_wrapped_block * bl
> while CFI_desc is the descriptor itself. */
> if (DECL_LANG_SPECIFIC (sym->backend_decl))
> CFI_desc = GFC_DECL_SAVED_DESCRIPTOR (sym->backend_decl);
> + else if (GFC_DESCRIPTOR_TYPE_P (TREE_TYPE (TREE_TYPE (sym->backend_decl))))
> + CFI_desc = sym->backend_decl;
> else
> CFI_desc = NULL;
>
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)
