llvm dev - Sep 2018 - OptBisect implementation for new pass manager

I'm concerned about codegen.  If Codegen is not yet ready for the new
PM, should the new PM really become default?  I would at least like to
see a plan of how Codegen is going to migrate before the new PM becomes
default.  Codegen pass pipelines have been wonky ever since I started
working with LLVM and it would be nice to get that cleaned up.

                            -David

Philip Pfaffe <philip.pfaffe at gmail.com> writes:
> Well, I think we don't have a clear idea about new-PM codegen should
> work in general. Is this really something that concerns us right now?
>
> Philip
>
> On Wed, Sep 26, 2018 at 7:54 PM Friedman, Eli
> <efriedma at codeaurora.org> wrote:
>
>     On 9/26/2018 10:47 AM, Philip Pfaffe via llvm-dev wrote:
>     > Hi Fedor,
>     >
>     > can you make an example where a pass actually needs to opt-out? 
>     > Because IMO, bisect should quite literally to DebugCounter-style
>     skip 
>     > every step in every ::run method's loop. Passes should not
even
>     be 
>     > concerned with this.
>     
>     This isn't so much an issue for the optimization pipeline, but
>     code 
>     generation involves some passes which are mandatory (e.g. isel).
>     
>     -Eli
>     
>     -- 
>     Employee of Qualcomm Innovation Center, Inc.
>     Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
>     a Linux Foundation Collaborative Project
>

I would really like to separate OptBisect and New-PM-by-default 
discussions! :)

regards,
   Fedor.

On 09/26/2018 09:13 PM, David Greene wrote:
> I'm concerned about codegen.  If Codegen is not yet ready for the new
> PM, should the new PM really become default?  I would at least like to
> see a plan of how Codegen is going to migrate before the new PM becomes
> default.  Codegen pass pipelines have been wonky ever since I started
> working with LLVM and it would be nice to get that cleaned up.
>
>                              -David
>
> Philip Pfaffe <philip.pfaffe at gmail.com> writes:
>
>> Well, I think we don't have a clear idea about new-PM codegen
should
>> work in general. Is this really something that concerns us right now?
>>
>> Philip
>>
>> On Wed, Sep 26, 2018 at 7:54 PM Friedman, Eli
>> <efriedma at codeaurora.org> wrote:
>>
>>      On 9/26/2018 10:47 AM, Philip Pfaffe via llvm-dev wrote:
>>      > Hi Fedor,
>>      >
>>      > can you make an example where a pass actually needs to
opt-out?
>>      > Because IMO, bisect should quite literally to
DebugCounter-style
>>      skip
>>      > every step in every ::run method's loop. Passes should
not even
>>      be
>>      > concerned with this.
>>      
>>      This isn't so much an issue for the optimization pipeline, but
>>      code
>>      generation involves some passes which are mandatory (e.g. isel).
>>      
>>      -Eli
>>      
>>      --
>>      Employee of Qualcomm Innovation Center, Inc.
>>      Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
>>      a Linux Foundation Collaborative Project
>>

But they're deeply connected.  I debug codegen problems all the time.
That opt-bisect doesn't work with codegen is really unfortunate.

If opt-bisect should work with codegen then we need to think about how
codegen will work with the new PM.

I agree that whether or not the new PM becomes default is somewhat
orthogonal but eventually it will and at that point I hope we have a
functioning opt-bisect for codegen.

                            -David

Fedor Sergeev <fedor.sergeev at azul.com> writes:
> I would really like to separate OptBisect and New-PM-by-default
> discussions! :)
>
> regards,
>   Fedor.
>
> On 09/26/2018 09:13 PM, David Greene wrote:
>> I'm concerned about codegen.  If Codegen is not yet ready for the
new
>> PM, should the new PM really become default?  I would at least like to
>> see a plan of how Codegen is going to migrate before the new PM becomes
>> default.  Codegen pass pipelines have been wonky ever since I started
>> working with LLVM and it would be nice to get that cleaned up.
>>
>>                              -David
>>
>> Philip Pfaffe <philip.pfaffe at gmail.com> writes:
>>
>>> Well, I think we don't have a clear idea about new-PM codegen
should
>>> work in general. Is this really something that concerns us right
now?
>>>
>>> Philip
>>>
>>> On Wed, Sep 26, 2018 at 7:54 PM Friedman, Eli
>>> <efriedma at codeaurora.org> wrote:
>>>
>>>      On 9/26/2018 10:47 AM, Philip Pfaffe via llvm-dev wrote:
>>>      > Hi Fedor,
>>>      >
>>>      > can you make an example where a pass actually needs to
opt-out?
>>>      > Because IMO, bisect should quite literally to
DebugCounter-style
>>>      skip
>>>      > every step in every ::run method's loop. Passes
should not even
>>>      be
>>>      > concerned with this.
>>>           This isn't so much an issue for the optimization
>>> pipeline, but
>>>      code
>>>      generation involves some passes which are mandatory (e.g.
isel).
>>>           -Eli
>>>           --
>>>      Employee of Qualcomm Innovation Center, Inc.
>>>      Qualcomm Innovation Center, Inc. is a member of Code Aurora
Forum,
>>>      a Linux Foundation Collaborative Project
>>>