[Libclc-dev] Beignet wants to apply libclc

[Tom Stellard]

On Wed, Sep 17, 2014 at 03:44:51PM +0800, He Junyan wrote:
> 
> On 二, 2014-09-16 at 10:33 -0400, Tom Stellard wrote:
> > On Tue, Sep 16, 2014 at 09:26:27PM +0800, He Junyan wrote:
> > > hi,
> > > 
> > > I am a developer of Intel's open source CL stack, which name is Beignet.
> > > We used to include all the CL built-ins in one huge header file and
> > > compile it as a PCH.
> > > We find some disadvantages of that manner and switched to the same
> > > manner as libclc recently. We now have a internal lib, which play the
> > > same role as the libclc, and we are attempting to apply the libclc to
> > > replace it in the near future.
> > > But I find some problems when I try to integrate the libclc:
> > > 1. There is no support for Image related functions in it now. Is that on
> > > your plan?
> > 
> > libclc only supports GPU targets and these targets require target-specific
> > implementations of the image functions, which is why there are no
> > generic image functions.  If you were to use libclc for Intel GPUs, you
> > would need to implement your own target specific image functions.
> > 
> OK, get it. The image module is really specific for each vendor and some
> of them do not want to expose the HW details to the public.
> 

In the case of AMD, it's not because we don't want to expose HW details.
We have already done this.  It's just that no one has had time to
implement the builtins yet.

> > > 2. I find it is not compatible with OpenCL1.2, which Beignet must
> > > support, are you going to implement it?
> > 
> > In what way is it not compatible?  The goal is to implement everything,
> > but as far as I know no one has spent much time on OpenCL 1.2 features.
> > 
> The beignet has declared the full support for 1.2, but if we use clc, we
> have to fallback to 1.1, this seems weird. 
> So far as I know, there are really some changes for CL APIs between 1.1
> and 1.2, but for the builtin functions and defines, the changes are not
> so big. The major changes are: adding 1d image and sampler-less image
> read functions, adding printf function, and adding extern and static
> keyword support. And the image module is even not included in clc, so I
> think this is not a big task to support 1.2, and I can do that job if
> you do not mind.
> 

Feel free to add any 1.2 features to libclc that you want.  As you say, I
don't think there are many changes in the builtin library from 1.1 to 1.2.

As for extern and static, this is handled by clang and not libclc.  If you
pass -cl-std=CL1.2 to clang, it should automatically enable these features.

-Tom


> > > 3. Because beignet as a backend does not completely follow the PTX or
> > > NVPTX framework, it has a lot of internal implementations for the
> > > builtin functions. We may need to add a lot of files for it, is that
> > > acceptable?
> > 
> > Yes, if you are adding a new target with a lot of target specific
> > implementations, then it is not a problem if there are a lot of files.
> > 
> OK, I will consider how to integrate our implementation and maximize the
> use of the clc's code.
> 
> > -Tom
> > 
> > > 
> > > 
> > > Thanks
> > > 
> > > 
> > > 
> > > 
> > > _______________________________________________
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> > > Libclc-dev at pcc.me.uk
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> 
> 
>