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Re: Help forging a function_decl


I run gcc with -fdump-tree-all-raw and found out that all dumps until
filename.c.013t.cfg are fine, but every time it fails, my function
disappears from filename.c.016t.ompexp onwards. Remembering: I want it
to happen every time there's a #pragma omp parallel in the source, so
I put my implementation right after the end of
c_parser_omp_parallel(), in file c-parser.c.

Again, thank you for the help.

---
Rodolfo Guilherme Wottrich
Universidade Estadual de Campinas - Unicamp


2013/7/22 Rodolfo Guilherme Wottrich <rgwott@gmail.com>:
> Hello,
>
> Thanks! I had solved the problem some days ago, and it was actually
> related to your answer.
> First, I hadn't used push_struct_function() to allocate storage for my
> new function.
> Second, I wasn't calling finish_function() after setting my tree, so
> it would not be further compiled (just like your suggestion, since
> cgraph_add_new_function is called inside it). As I was inside the
> scope of main(), I also needed to save the function context with
> push_function_context(), call finish_function() and then pop the
> context back.
> Third, the flag DECL_EXTERNAL for my function was being set, so even
> though my tree was going to be further compiled, the definition for my
> function_decl was to be found outside file scope.
>
> Now the problem is solved, but I still face an odd behavior: sometimes
> my function is output, sometimes not. Basically 50% of the times I
> compile my code, my function is simply not output. And when I try to
> debug gcc with gdb, it always fails.
> Any thoughts? Maybe I am missing something related to garbage
> collection or so... Not a clue.
>
> ---
> Rodolfo Guilherme Wottrich
> Universidade Estadual de Campinas - Unicamp
>
>
> 2013/7/22 Martin Jambor <mjambor@suse.cz>:
>> Hi,
>>
>> On Wed, Jul 17, 2013 at 04:52:30PM -0300, Rodolfo Guilherme Wottrich wrote:
>>> Hello there,
>>>
>>> Please disregard this message in case it doesn't fit here.
>>>
>>> During compilation of a C file, I need to be able to create a global
>>> function definition, with whatever a body I may have forged. I mean,
>>> the function is not going to be present in the source file and I got
>>> to create the respective tree structure so it can be later gimplified
>>> and further compiled like any other function present in the source. I
>>> would only need to create that function in case some OpenMP directive
>>> is encountered, so my latest and unsuccessful try to do so was to
>>> create the tree structures for a FUNCTION_DECL and, say, a variable
>>> declared inside the scope of that function, after the parsing of a
>>> #pragma omp parallel in c_parser_omp_parallel() in file c-parser.c. I
>>> followed and tried to re-create the steps I found in the function
>>> create_omp_child_function(), in file omp-low.c, and
>>> http://gcc.gnu.org/onlinedocs/gccint/Function-Basics.html#Function-Basics.
>>>
>>> I think maybe the problem is that my new function doesn't go under
>>> rest_of_compilation, therefore it is not gimplified and obviously no
>>> code for it is generated.
>>
>> it's a bit difficult to say without knowing what you are doing and at
>> what compilation stage you are doing it but perhaps you could try
>> calling cgraph_add_new_function on the new decl?  Also try reading the
>> comment at the beginning of cgraphunit.c.
>>
>> Hope it helps,
>>
>> Martin
>>
>>
>>>
>>> Summarizing: I tried to forge a function in parsing time, but
>>> couldn't. What am I doing wrong, and how can one do such a thing?
>>> Maybe the problem is that I create no calls to that new function, what
>>> do you think? Anyway, I'm compiling with -O0, so I guess no
>>> optimization pass would remove my function just because it is not
>>> being used.
>>>
>>> Thanks in advance,
>>>
>>> ---
>>> Rodolfo Guilherme Wottrich
>>> Universidade Estadual de Campinas - Unicamp


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