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Re: [PATCH] Convert more passes to new dump framework


On 30 August 2013 23:23:16 Teresa Johnson <tejohnson@google.com> wrote:
On Fri, Aug 30, 2013 at 1:30 PM, Xinliang David Li <davidxl@google.com> wrote:
> On Fri, Aug 30, 2013 at 12:51 PM, Teresa Johnson <tejohnson@google.com> wrote: >> On Fri, Aug 30, 2013 at 9:27 AM, Xinliang David Li <davidxl@google.com> wrote:
>>> Except that in this form, the dump will be extremely large and not
>>> suitable for very large applications.
>>
>> Yes. I did some measurements for both a fairly large source file that
>> is heavily optimized with LIPO and for a simple toy example that has
>> some inlining. For the large source file, the output from
>> -fdump-ipa-inline=stderr was almost 100x the line count of the
>> -fopt-info output. For the toy source file it was 43x. The size of the
>> -details output was 250x and 100x, respectively. Which is untenable
>> for a large app.
>>
>> The issue I am having here is that I want a more verbose message, not
>> a more voluminous set of messages. Using either -fopt-info-all or
>> -fdump-ipa-inline to provoke the more verbose inline message will give
>> me a much greater volume of output.
>>
>> One compromise could be to emit the more verbose inliner message under
>> a param (and a more concise "foo inlined into bar" by default with
>> -fopt-info). Or we could do some variant of what David talks about
>> below.
>
> something like --param=verbose-opt-info=1

Yes. Richard, would this be acceptable for now?

i.e. the inliner messages would be like:

-fopt-info:
   "test.c:8:3: note: foobar inlined into foo with call count 99999000"
(the "with call count X" only when there is profile feedback)

-fopt-info --param=verbose-opt-info=1:
   "test.c:8:3: note: foobar/0 (99999000) inlined into foo/2 (1000)
with call count 99999000 (via inline instance bar [3] (99999000))
(again the call counts only emitted under profile feedback)

Assuming the [3] is order, please change that to match what the in liner uses, I.e. /3

Thanks

>
>
>>
>>> Besides, we might also want to
>>> use the same machinery (dump_printf_loc etc) for dump file dumping.
>>> The current behavior of using '-details' to turn on opt-info-all
>>> messages for dump files are not desirable.
>>
>> Interestingly, this doesn't even work. When I do
>> -fdump-ipa-inline-details=stderr (with my patch containing the inliner
>> messages) I am not getting those inliner messages emitted to stderr.
>> Even though in dumpfile.c "details" is set to (TDF_DETAILS |
>> MSG_OPTIMIZED_LOCATIONS | MSG_MISSED_OPTIMIZATION | MSG_NOTE). I'm not
>> sure why, but will need to debug this.
>
> It works for vectorizer pass.

Ok, let me see what is going on - I just confirmed that it is not
working for the loop unroller messages either.

>
>>
>>> How about the following:
>>>
>>> 1) add a new dump_kind modifier so that when that modifier is
>>> specified, the messages won't goto the alt_dumpfile (controlled by
>>> -fopt-info), but only to primary dump file. With this, the inline
>>> messages can be dumped via:
>>>
>>>    dump_printf_loc (OPT_OPTIMIZED_LOCATIONS | OPT_DUMP_FILE_ONLY, .....)
>>
>> (you mean (MSG_OPTIMIZED_LOCATIONS | OPT_DUMP_FILE_ONLY) )
>>
>
> Yes.
>
>> Typically OR-ing together flags like this indicates dump under any of
>> those conditions. But we could implement special handling for
>> OPT_DUMP_FILE_ONLY, which in the above case would mean dump only to
>> the primary dump file, and only under the other conditions specified
>> in the flag (here under "-optimized")
>>
>>>
>>>
>>> 2) add more flags in -fdump- support:
>>>
>>>    -fdump-ipa-inline-opt   --> turn on opt-info messages only
>>>    -fdump-ipa-inline-optall --> turn on opt-info-all messages
>>
>> According to the documentation (see the -fdump-tree- documentation on
>> http://gcc.gnu.org/onlinedocs/gcc/Debugging-Options.html#Debugging-Options),
>> the above are already supposed to be there (-optimized, -missed, -note
>> and -optall). However, specifying any of these gives a warning like:
>>    cc1: warning: ignoring unknown option âoptimizedâ in
>> â-fdump-ipa-inlineâ [enabled by default]
>> Probably because none is listed in the dump_options[] array in dumpfile.c.
>>
>> However, I don't think there is currently a way to use -fdump- options
>> and *only* get one of these, as much of the current dump output is
>> emitted whenever there is a dump_file defined. Until everything is
>> migrated to the new framework it may be difficult to get this to work.
>>
>>>    -fdump-tree-pre-ir --> turn on GIMPLE dump only
>>>    -fdump-tree-pre-details --> turn on everything (ir, optall, trace)
>>>
>>> With this, developers can really just use
>>>
>>>
>>> -fdump-ipa-inline-opt=stderr for inline messages.
>>
>> Yes, if we can figure out a good way to get this to work (i.e. only
>> emit the optimized messages and not the rest of the dump messages).
>> And unfortunately to get them all you need to specify
>> "-fdump-ipa-all-optimized -fdump-tree-all-optimized
>> -fdump-rtl-all-optimized" instead of just -fopt-info. Unless we can
>> add -fdump-all-all-optimized.
>
> Having general support requires cleanup of all the old style  if
> (dump_file) fprintf (dump_file, ...) instances to be:
>
>   if (dump_enabled_p ())
>     dump_printf (dump_kind ....);

Right. But that is going to be a big longer-term effort - grepping for
dump_file in gcc/*.c gives about 6000 instances.

>
>
> However, it might be easier to do this filtering for IR dump only (in
> execute_function_dump) -- do not dump IR if any of the MSG_xxxx is
> specified unless IR flag (a new flag) is also specified.

Unfortunately there are a lot of messages that are not from
execute_function_dump.

Thanks,
Teresa

>
> David
>
>
>>
>> Teresa
>>
>>>
>>> thanks,
>>>
>>> David
>>>
>>> On Fri, Aug 30, 2013 at 1:30 AM, Richard Biener
>>> <richard.guenther@gmail.com> wrote:
>>>> On Thu, Aug 29, 2013 at 5:15 PM, Teresa Johnson <tejohnson@google.com> wrote:
>>>>> On Thu, Aug 29, 2013 at 3:04 AM, Richard Biener
>>>>> <richard.guenther@gmail.com> wrote:
>>>>>>>>> New patch below that removes this global variable, and also outputs
>>>>>>>>> the node->symbol.order (in square brackets after the function name so
>>>>>>>>> as to not clutter it). Inline messages with profile data look look:
>>>>>>>>>
>>>>>>>>> test.c:8:3: note: foobar [0] (99999000) inlined into foo [2] (1000)
>>>>>>>>> with call count 99999000 (via inline instance bar [3] (99999000))
>>>>>>>>
>>>>>>>> Ick.  This looks both redundant and cluttered.  This is supposed to be
>>>>>>>> understandable by GCC users, not only GCC developers.
>>>>>>>
>>>>>>> The main part that is only useful/understandable to gcc developers is
>>>>>>> the node->symbol.order in square brackes, requested by Martin. One
>>>>>>> possibility is that I could put that part under a param, disabled by
>>>>>>> default. We have something similar on the google branches that emits
>>>>>>> LIPO module info in the message, enabled via a param.
>>>>>>
>>>>>> But we have _dump files_ for that.  That's the developer-consumed
>>>>>> form of opt-info. -fopt-info is purely user sugar and for usual translation
>>>>>> units it shouldn't exceed a single terminal full of output.
>>>>>
>>>>> But as a developer I don't want to have to parse lots of dump files
>>>>> for a summary of the major optimizations performed (e.g. inlining,
>>>>> unrolling) for an application, unless I am diving into the reasons for
>>>>> why or why not one of those optimizations occurred in a particular
>>>>> location. I really do want a summary emitted to stderr so that it is
>>>>> easily searchable/summarizable for the app as a whole.
>>>>>
>>>>> For example, some of the apps I am interested in have thousands of
>>>>> input files, and trying to collect and parse dump files for each and
>>>>> every one is overwhelming (it probably would be even if my input files
>>>>> numbered in the hundreds). What has been very useful is having these
>>>>> high level summary messages of inlines and unrolls emitted to stderr
>>>>> by -fopt-info. Then it is easy to search and sort by hotness to get a
>>>>> feel for things like what inlines are missing when moving to a new
>>>>> compiler, or compiling a new version of the source, for example. Then
>>>>> you know which files to focus on and collect dump files for.
>>>>
>>>> I thought we can direct dump files to stderr now?  So, just use
>>>> -fdump-tree-all=stderr
>>>>
>>>> and grep its contents.
>>>>
>>>>>>
>>>>>>> I'd argue that the other information (the profile counts, emitted only
>>>>>>> when using -fprofile-use, and the inline call chains) are useful if
>>>>>>> you want to understand whether and how critical inlines are occurring.
>>>>>>> I think this is the type of information that users focused on
>>>>>>> optimizations, as well as gcc developers, want when they use
>>>>>>> -fopt-info. Otherwise it is difficult to make sense of the inline
>>>>>>> information.
>>>>>>
>>>>>> Well, I doubt that inline information is interesting to users unless we are >>>>>> able to aggressively filter it to what users are interested in. Which IMHO >>>>>> isn't possible - users are interested in "I have not inlined this even though
>>>>>> inlining would severely improve performance" which would indicate a bug
>>>>>> in the heuristics we can reliably detect and thus it wouldn't be there.
>>>>>
>>>>> I have interacted with users who are aware of optimizations such as
>>>>> inlining and unrolling and want to look at that information to
>>>>> diagnose performance differences when refactoring code or using a new
>>>>> compiler version. I also think inlining (especially cross-module) is
>>>>> one example of an optimization that is still being tuned, and user
>>>>> reports of performance issues related to that have been useful.
>>>>>
>>>>> I really think that the two groups of people who will find -fopt-info
>>>>> useful are gcc developers and savvy performance-hungry users. For the
>>>>> former group the additional info is extremely useful. For the latter
>>>>> group some of the extra information may not be required (although a
>>>>> call count is useful for those using profile feedback), but IMO is not
>>>>> unreasonable.
>>>>
>>>> well, your proposed output wrecks my 80x24 terminal already due to overly
>>>> long lines.
>>>>
>>>> In the end we may up with a verbosity level for each sub-set of opt-info
>>>> messages.  Ick.
>>>>
>>>> Richard.
>>>>
>>>>> Teresa
>>>>>
>>>>>
>>>>> --
>>>>> Teresa Johnson | Software Engineer | tejohnson@google.com | 408-460-2413
>>
>>
>>
>> --
>> Teresa Johnson | Software Engineer | tejohnson@google.com | 408-460-2413



--
Teresa Johnson | Software Engineer | tejohnson@google.com | 408-460-2413


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