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Re: Iterating over RTL in Graphite

On Mon, Mar 5, 2012 at 3:52 PM, Arnaldo <> wrote:
> On Mon, Mar 5, 2012 at 10:00 AM, Michael Matz <> wrote:
>> Hi,
>> On Mon, 5 Mar 2012, Arnaldo wrote:
>>> I couldn't get cfgexpand.c:basic_block expand_gimple_basic_block
>>> (basic_block bb) to work by calling it directly because there is some
>>> preprocessing in gimple_expand_cfg() that has to be done first. ?But
>>> calling gimple_expand_cfg() modifies the CFG and asserts will fail later
>>> on during compilation.
>>> I think the only way to solve this would be to somehow duplicate the
>>> current cfun structure when entering the part of Graphite I'm extending,
>>> then calling push_cfun(), gimple_expand_cfg(), extracting the BBs with
>>> the RTL and calling pop_cfun() before continuing.
>> Really, you're barking up the wrong tree. ?graphite doesn't work on the
>> RTL IL, it'll work only on gimple. ?expanding is what we call the process
>> of transforming gimple to RTL, and that process destroys gimple. ?Hence
>> you can't do that when still at the gimple side of things as there are
>> still passes to run that run in gimple.
>> Whatever you want to do with graphite, you have to do it at the gimple
>> level.
>> Ciao,
>> Michael.
> Richard, Michael,
> I have to find a way to generate the RTL because I have profiled an
> instruction set and I need access to these costs during my extension
> to the Graphite pass. ?I planed to add these costs as attributes to
> the RTX patterns in the machine description file and read the back
> from Graphite. ?Gimple seems to be too high-level to associate its
> statements to machine costs.

Graphite (polyhedral form) is even more high-level, how do you expect
RTX costs to be meaningful there at all?

> I know this is not the way GCC was designed but the optimization I'm
> working on needs access to the profile. ?Maybe there's a better way of
> doing this? ?What I'm attempting to do now is to duplicate the current
> cfun so that I can expand and read the RTL attributes and then discard
> this cfun before continuing with the compilation.

I don't even see how you could compute a reliable mapping of Graphite
(or GIMPLE) to the RTL you generate that way.


> -Arnaldo

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