On Mar 20, 2012, at 1:21 PM, Richard Guenther wrote:
> On Tue, 20 Mar 2012, Tristan Gingold wrote:
>> On Mar 15, 2012, at 10:37 AM, Richard Guenther wrote:
>>> On Wed, 14 Mar 2012, Tristan Gingold wrote:
>>> Well. To make this work in LTO the "main" function (thus, the program
>>> entry point) should be marked at cgraph level and all users of
>>> MAIN_NAME_P should instead check a flag on the cgraph node.
>>>> Will write a predicate in tree.[ch].
>>> Please instead transition "main-ness" to the graph.
>> here is the patch I wrote. Does it match what you had in mind ?
> Basically yes. Comments below.
>> main_identifier_node is now set in tree.c
> Looks good, hopefully my review-grep was as good as yours ;)
>> diff --git a/gcc/cfgexpand.c b/gcc/cfgexpand.c
>> index bd21169..7a7a774 100644
>> --- a/gcc/cfgexpand.c
>> +++ b/gcc/cfgexpand.c
>> @@ -4513,9 +4513,8 @@ gimple_expand_cfg (void)
>> /* If this function is `main', emit a call to `__main'
>> to run global initializers, etc. */
>> - if (DECL_NAME (current_function_decl)
>> - && MAIN_NAME_P (DECL_NAME (current_function_decl))
>> - && DECL_FILE_SCOPE_P (current_function_decl))
>> + if (DECL_FILE_SCOPE_P (current_function_decl)
>> + && cgraph_main_function_p (cgraph_get_node (current_function_decl)))
>> expand_main_function ();
> The DECL_FILE_SCOPE_P check is redundant, please remove them everywhere
> you call cgraph_main_function_p. I suppose returning false if the
> cgraph node is NULL in cgraph_main_function_p would be good.
Ok. (I added the DECL_FILE_SCOPE_P check to avoid the cgraph lookup for speed
>> diff --git a/gcc/cgraphunit.c b/gcc/cgraphunit.c
>> index 516f187..4a59f63 100644
>> --- a/gcc/cgraphunit.c
>> +++ b/gcc/cgraphunit.c
>> @@ -346,6 +346,10 @@ cgraph_finalize_function (tree decl, bool nested)
>> notice_global_symbol (decl);
>> node->local.finalized = true;
>> node->lowered = DECL_STRUCT_FUNCTION (decl)->cfg != NULL;
>> + node->local.main_function =
>> + DECL_FILE_SCOPE_P (decl)
>> + && ((!DECL_ASSEMBLER_NAME_SET_P (decl) && MAIN_NAME_P (DECL_NAME
>> + || decl_assembler_name_equal (decl, main_identifier_node));
> If we finalize a function we should always create an assembler name,
> thus I'd change the above to
> node->local.main_function = decl_assembler_name_equal (decl,
Indeed. At worst, the assembler name is created during the call to
> btw, decl_assembler_name_equal doesn't seem to remove target-specific
> mangling - do some OSes "mangle" main differently (I'm thinking of
> leading underscores or complete renames)? Thus, I guess the
> targets might want to be able to provide the main_identifier_assember_name
> you use here.
I think this is currently OK because decl_assembler_name_equal deals
with leading underscore correctly. I have checked that on Darwin,
which has a leading underscore.
The only target that mangle names is i386 cygwin/mingw, which 'annotates'
stdcall and fastcall function, but main() is regular.
But I agree this mechanism is fragile.
In order to make this mechanism stronger, we could add main_function_node, which
designates the FUNCTION_DECL that is the main function (if not NULL_TREE), with
a fallback on main_identifier_node for regular languages such as C or C++.