[Mesa-dev] Unused (?) duplicated GLSL IR state in NIR

[Emil Velikov]

On 2 November 2015 at 19:41, Jason Ekstrand <jason at jlekstrand.net> wrote:
> On Mon, Nov 2, 2015 at 9:33 AM, Connor Abbott <cwabbott0 at gmail.com> wrote:
>> On Mon, Nov 2, 2015 at 8:35 AM, Emil Velikov <emil.l.velikov at gmail.com> wrote:
>>> Hi all,
>>>
>>> From a quick look, it seems that NIR copies (almost ?) all the state
>>> from GLSL IR even if it doesn't use it.
>>>
>>> The particular piece that I'm thinking about is nir_variable::data.
>>> Afaict this is a remnant from the early days, when the intent was to
>>> kill off the GLSL IR and use NIR directly. If so should we just nuke
>>> it, or (if there is someone working on it) add some comments "Keepme:
>>> WIP work by XXX to use this and kill the glsl IR one".
>>>
>>> The (not that distant) GLSL IR memory optimisations by Ian, seems to
>>> have missed NIR. Was that intentional or were those worked upon before
>>> NIR got merged ? Perhaps it's worth porting them over ?
>>>
>>>
>>> Thanks
>>> Emil
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>>
>> Hi Emil,
>>
>> Indeed, nir_variable was copied from ir_variable before Ian's memory
>> optimizations landed. Also, as you noticed, there are a number of
>> fields only used by the GLSL linker, so they're unused until/unless we
>> do linking in NIR. I wouldn't be opposed to nuking those, since we can
>> always revert the commit if/when we get to that.
>
> Agreed.  If you want to nuke some of them, feel free to send the
> patch.  If you do, please CC me.  There are some things that we're
> using for SPIR-V so I might request that you keep a field or two.
> However, cleaning it up would definitely be a good idea.
>
> One thing I will note though is that you should consider this a
> cleanup and not an optimization.  The reason why Ian's stuff helped
> GLSL IR so much is that it uses variables extensively.  The average
> NIR shader only has about half a dozen variables by the time you get
> done optimizing so it's not nearly as much of a problem.
Ack. Thanks guys. So currently no-one is pursuing move the linking to NIR ?

On the optimisation vs cleanup note - it'll be tiny bit of both.

-Emil