Re: how to make sure an init routine is kept in the call graph?

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

On Fri, Apr 22, 2011 at 8:35 AM, Gary Funck <gary@intrepid.com> wrote:
>
> Recently, we tried to merge the GCC trunk into the GUPC branch
> and ran into an issue caused by a recent GCC update.
> The last successful merge was trunk version 172359, fyi.
>
> For certain UPC file scope static initializers,
> a per file initialization routine is created, its address
> is added to a global table (in its own section).
> The UPC runtime will call all the routines listed in that
> table before transferring control the user's main program.
>
> After the recent trial merge, we see the following on
> some of our test cases:
>
> ../../gcc/xupc -O2 -g -fdump-ipa-cgraph -fdump-tree-cfg test25.upc -o test25
> /tmp/ccygQ8JN.o:(upc_init_array+0x0): undefined reference to `__upc_init_decls'
>
> The call graph dump entry for `__upc_init_decls' is as follows:
>
> __upc_init_decls/80(80) @0x7ffff1eb3de0 (asm: __upc_init_decls) body finalized
> ?called by:
> ?calls:
> ?References:
> ?Refering this function:
>
> As expected, no explicit references have been recorded.
>
> The compiler routine that creates this initialization routine is
> called from c_common_parse_file():
>
> ? ? ?push_file_scope ();
> ? ? ?c_parse_file ();
> ? ? ?/* Generate UPC global initialization code, if required. ?*/
> ? ? ?if (c_dialect_upc ())
> ? ? ? ?upc_write_global_declarations ();
> ? ? ?pop_file_scope ();
>
> The routine that builds the initialization function is
> upc_build_init_func() in gcc/upc/upc-act.c (on the gupc branch).
> This routine does the following to build the function,
> mark it as used and referenced, and to then add its address
> to the initialiaztion table:
>
> ?DECL_SOURCE_LOCATION (current_function_decl) = loc;
> ?TREE_PUBLIC (current_function_decl) = 0;
> ?TREE_USED (current_function_decl) = 1;
> ?DECL_SECTION_NAME (current_function_decl) =
> ? ? build_string (strlen (UPC_INIT_SECTION_NAME), UPC_INIT_SECTION_NAME);
> ?/* Swap the statement list that we've built up,
> ? ? for the current statement list. ?*/
> ?t_list = c_begin_compound_stmt (true);
> ?TREE_CHAIN (stmt_list) = TREE_CHAIN (t_list);
> ?cur_stmt_list = stmt_list;
> ?free_stmt_list (t_list);
> ?t_list = c_end_compound_stmt (loc, stmt_list, true);
> ?add_stmt (t_list);
> ?finish_function ();
> ?gcc_assert (DECL_RTL (init_func));
> ?upc_init_array_section = get_section (UPC_INIT_ARRAY_SECTION_NAME,
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?0, NULL);
> ?mark_decl_referenced (init_func);
> ?init_func_symbol = XEXP (DECL_RTL (init_func), 0);
> ?assemble_addr_to_section (init_func_symbol, upc_init_array_section);
>
> In the past, setting TREE_USED() and calling mark_decl_referenced()
> was sufficient to make sure that this routine was not removed from the
> call graph.
>
> What is needed in the new scheme of things to ensure that this
> initialization function stays in the call graph?

Try setting DECL_PRESERVE_P to 1.

Richard.

> thanks,
>
> - Gary
>