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

[Xinliang David Li <davidxl at google dot com>]

Except that in this form, the dump will be extremely large and not
suitable for very large applications. 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.  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, .....)


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
   -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.

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