[Beignet] Building beignet with OpenCL 2.0 support in distros

[Rebecca N. Palmer]

On 21/01/17 15:40, Bruno Pagani wrote:
> Le 21/01/2017 à 16:20, Rebecca N. Palmer a écrit :
>
>>> is there any downside in compiling with
>>> OpenCL 2.0 support,
>> Yes - on older (Ivybridge/Haswell - no emitUntypedReadA64Instruction)
>> hardware, a 2.0-enabled beignet won't work, at all.
>
> That’s what I’ve feared but after trying it here I haven’t encountered
> more issues than with a non-2.0-enabled beignet.

Trying it on what hardware?  There might be hardware (all of gen8 if 
this assert(0) is the only failure point) where a 2.0 build doesn't 
crash outright but also doesn't have working 2.0.

> What would be the point of installing both [2.0 and non-2.0]? Just so that softwares not
> needing 2.0 don’t get hurt on performances?

That, and users (of software with non-broken empty platform handling) 
not having to think about which one they actually need.  (I discovered 
the existence of broken empty platform handling while considering 
whether to create an opencl-icd-all package, which would depend on 
beignet, mesa-opencl-icd and pocl.)

>> I at least need to decide quickly, as Debian freezes this week.
> But does that really applies to Debian?
> Because AFAIU, there is no llvm 3.9 in Debian Stretch:

There is LLVM 3.9 in Debian Stretch (I already build beignet with it), 
it just isn't the default (the one that gets the plain 'llvm' name): 
https://packages.debian.org/stretch/llvm-3.9