Basic Block Statistics

Will Hawkins
Wed May 17 18:41:00 GMT 2017

On Wed, May 17, 2017 at 1:04 PM, Will Hawkins <> wrote:
> On Wed, May 17, 2017 at 1:02 PM, Jeff Law <> wrote:
>> On 05/17/2017 10:36 AM, Will Hawkins wrote:
>>> As I started looking into this, it seems like PLUGIN_FINISH is where
>>> my plugin will go. Everything is great so far. However, when plugins
>>> at that event are invoked, they get no data. That means I will have to
>>> look into global structures for information regarding the compilation.
>>> Are there pointers to the documentation that describe the relevant
>>> global data structures that are accessible at this point?
>>> I am looking through the source code and documentation and can't find
>>> what I am looking for. I am happy to continue working, but thought I'd
>>> ask just in case I was missing something silly.
>>> Thanks again for all your help getting me started on this!
>> FOR_EACH_BB (bb) is what you're looking for.  That will iterate over the
>> basic blocks.
> Thank you so much for your response!
> I just found this as soon as you sent it. Sorry for wasting your time!
>> Assuming you're running late, you'll then want to walk each insn within
>> the bb.  So something like this
>> basic_block bb
>> FOR_EACH_BB (bb)
>>   {
>>     rtx_insn *insn;
>>     FOR_BB_INSNS (bb, insn)
>>       {
>>         /* Do something with INSN.  */
>>       }
>>   }
>> Note that if you're running too late the CFG may have been released, in
>> which case this code wouldn't do anything.

This macro seems to require that there be a valid cfun. This seems to
imply that the macro will work only where the plugin callback is
invoked before/after a pass that does some optimization for a
particular function. In particular, at PLUGIN_FINISH, cfun is NULL.
This makes perfect sense.

Since PLUGIN_FINISH is the place where diagnostics are supposed to be
printed, I was wondering if there was an equivalent iterator for all
translation units (from which I could derive functions, from which I
could derive basic blocks) that just "FINISH"ed compiling?

The other way to approach the problem, I suppose, is to just
accumulate those stats at the end of each pass execution phase and
then simply print them when PLUGIN_FINISH is invoked.

I'm sorry to make this so difficult. I am just wondering about the way
that the community expects the plugins to be written in the most
modular fashion.

Thanks again for walking me through all this!

> I will just have to experiment to see exactly when the right time to
> invoke this plugin to get the best data.
> Thanks again!
> Will
>> jeff

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