[PATCH] Add a callback to FunctionPass to enable skipping execution on a per-function basis

[Chandler Carruth]

I meant either a predicate lambda, or a flag that gates hard-coded
subtarget queries inside the pass, whichever makes more sense.

On Wed, Apr 8, 2015 at 8:18 PM Eric Christopher <echristo at gmail.com> wrote:

> Or do you mean a predicate lambda passed during pass construction? I'd be
> totally down with that.
>
> On Wed, Apr 8, 2015, 8:17 PM Eric Christopher <echristo at gmail.com> wrote:
>
>>
>> How would that work? A parameter doesn't get us subtarget Independence in
>> the pass manager construction as far as I can tell. I could be dense here
>> though.
>>
>> On Wed, Apr 8, 2015, 8:10 PM Chandler Carruth <chandlerc at google.com>
>> wrote:
>>
>>> I'm suggesting rather than a decorator, we use an optional predicate
>>> parameter when constructing the pass. To me, that seems somewhat cleaner.
>>>
>>> On Wed, Apr 8, 2015 at 8:09 PM Eric Christopher <echristo at gmail.com>
>>> wrote:
>>>
>>>> Right, I agree with this in general, but looking to avoid the weird
>>>> subtarget flags that I mentioned. Perhaps we should revisit Akira's
>>>> original idea of wrapping pass in a decorator if you want to pull it out of
>>>> the pass manager machinery?
>>>>
>>>> On Wed, Apr 8, 2015, 8:04 PM Chandler Carruth <chandlerc at google.com>
>>>> wrote:
>>>>
>>>>> Actually, even this could be done cleanly.
>>>>>
>>>>> You could change the *pass* to accept the generic predicate in this
>>>>> case, and add one unpredicated version to the pipeline and add a predicated
>>>>> form later.
>>>>>
>>>>> I'm essentially trying to lift the predicate logic out of the pass
>>>>> management machinery and into the pass itself because that's where the
>>>>> motivation for a predicate comes from.
>>>>>
>>>>> On Wed, Apr 8, 2015 at 8:03 PM Chandler Carruth <chandlerc at google.com>
>>>>> wrote:
>>>>>
>>>>>> Is this a real use case or a hypothetical one? Because it seems
>>>>>> somewhat contrived to me...
>>>>>>
>>>>>> If there really is some predicate that necessitates really radically
>>>>>> different pass pipelines, I feel like they should be, well, two separate
>>>>>> pass pipelines.
>>>>>>
>>>>>> On Wed, Apr 8, 2015 at 7:54 PM Eric Christopher <echristo at gmail.com>
>>>>>> wrote:
>>>>>>
>>>>>>> Optnone, IMO, needs to be replaced by something less terrible.
>>>>>>>
>>>>>>> I'm not sure how this is going to work with the "I want to run the
>>>>>>> first cfgcleanup unconditionally, but not the second" without tying the
>>>>>>> subtargets to things like shouldRunCfgCleanup2().
>>>>>>>
>>>>>>> On Wed, Apr 8, 2015, 7:38 PM Sean Silva <chisophugis at gmail.com>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> Adding Paul as this seems related to optnone.
>>>>>>>>
>>>>>>>> On Wed, Apr 8, 2015 at 7:31 PM, Chandler Carruth <
>>>>>>>> chandlerc at gmail.com> wrote:
>>>>>>>>
>>>>>>>>> I feel like we could do something much simpler than this. This
>>>>>>>>> feeling is predicated on one primary theory: most passes will run for most
>>>>>>>>> subtargets. Put another way, there will only be a small number of passes
>>>>>>>>> that we actually want to opt out of on a per-subtarget basis.
>>>>>>>>>
>>>>>>>>> If we think that's likely to be the case, here is an alternative
>>>>>>>>> suggestion:
>>>>>>>>>
>>>>>>>>> - Add bool-returning predicates for each pass to the subtarget
>>>>>>>>> base class (eg, "isIfConversionProfitable()") with the expected default
>>>>>>>>> ("true").
>>>>>>>>> - Override these for the subtargets that want to opt out.
>>>>>>>>> - Change the pass to directly get the subtarget, query it, and
>>>>>>>>> bail without doing anything if it gets "false".
>>>>>>>>>
>>>>>>>>> From looking at and thinking about if-conversion at least, this
>>>>>>>>> seems nicer to me. It makes someone working on the pass aware that there
>>>>>>>>> are subtarget profitability concerns, and it makes it very clear that we
>>>>>>>>> are *running* all of the passes, just that some have no effect on certain
>>>>>>>>> subtargets.
>>>>>>>>>
>>>>>>>>> This also matches how an optimization pass should query the
>>>>>>>>> function for the 'noopt' attribute and bail.
>>>>>>>>>
>>>>>>>>> Thoughts?
>>>>>>>>>
>>>>>>>>
>>>>>>>>>
>>>>>>>>> http://reviews.llvm.org/D8717
>>>>>>>>>
>>>>>>>>> EMAIL PREFERENCES
>>>>>>>>>   http://reviews.llvm.org/settings/panel/emailpreferences/
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> _______________________________________________
>>>>>>>>> llvm-commits mailing list
>>>>>>>>> llvm-commits at cs.uiuc.edu
>>>>>>>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>>>>>>>>>
>>>>>>>> _______________________________________________
>>>>>>> llvm-commits mailing list
>>>>>>> llvm-commits at cs.uiuc.edu
>>>>>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>>>>>>>
>>>>>>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150409/51704bb8/attachment.html>