Iterating over RTL in Graphite

[Tobias Grosser]

On 02/17/2012 08:34 PM, David Malcolm wrote:
> On Thu, 2012-02-16 at 19:17 -0400, Arnaldo wrote:
>> Hello everyone,
>>
>> I'm working on an extension to the Graphite pass of GCC 4.4.0.  My
>> intention is to associate costs to RTL instructions by adding them as
>> RTX attributes to a machine description file, and to read them back
>> during the Graphite pass by iterating through each basic block.
>>
>> Is the RTL available during this optimization pass? I'm not sure this
>> is the case as I get a segfault when trying to iterate over the RTL
>> with the code below ("internal compiler error: Segmentation fault"). I
>> don't need the fully resolved RTL, just to be able to read the
>> attribute given an RTL instruction.
>>
>> I've tried debugging the compiler with gdb but it can't find the
>> debugging symbols even though they're there.  I'll keep trying to get
>> gdb to work but any leads on reading these attributes from within
>> Graphite is greatly appreciated.
> I don't know about GCC 4.4, but a while back I wrote a script using my
> GCC Python plugin to draw a "subway map" of GCC 4.6's passes:
> http://gcc.gnu.org/ml/gcc/2011-07/msg00157.html
> which you can see here:
> http://gcc-python-plugin.readthedocs.org/en/latest/tables-of-passes.html
>
> If I reading things correctly, the graphite passes happen whilst the
> code is still in gimple form: the blocks are converted to RTL form in
> the "expand" pass, which happens about 20 or so passes later.
>
> Caveat: I'm not familiar with the insides of the graphite, and am
> relatively new to gcc's insides, so I could be wrong; also the script
> relies on the pass flags, and they're not necessarily correct either...

Yes, graphite works on GIMPLE. I believe I have never seen RTL when 
working on graphite, so I doubt it is easily available. (Maybe it is, 
but it is definitely not used within graphite).

Cheers
Tobi