[Mesa-dev] [cfe-dev] 3 element vectors in opencl 1.1+

[Jan Vesely]

On Wed, 2014-04-23 at 19:49 +0200, Francisco Jerez wrote:
> Jan Vesely <jan.vesely at rutgers.edu> writes:
> 
> > On Tue, 2014-04-22 at 17:50 -0700, Matt Arsenault wrote:
> > <snip>
> >
> >> >> I think this is what v96:128 is for
> >> > according to [0], it specifies only alignment, not size. I could not
> >> > find an __attribute__ that would change size either.
> >> >
> >> > It should be possible to have ADMGPUDataLayout: public DataLayout class
> >> > that would intercept the call and fix the reported value, but I think it
> >> > would only move the hack to different place.
> >> >
> >> > I have added pocl-devel list as suggested.
> >> >
> >> > regards,
> >> > Jan
> >> >
> >> > [0]http://llvm.org/docs/LangRef.html#data-layout
> >> >
> >> 
> >> Only the size in memory matters, which is what the required alignment 
> >> specifies. DataLayout::getTypeAllocSize accounts for the alignment, but 
> >> getTypeStoreSize does not. I actually thought this was half of what 
> >> getTypeStoreSize was for, but it turns out it isn't.
> >
> > hm, I always thought that alignment only puts restrictions on starting
> > address and using padding was just a tool to do the job.
> >
> > anyway, thanks for the hint, using getTypeAllocSize works nicely.
> > since we are allocating space in the argument vector I think
> > getAllocSize is the right function to use.
> >
> > I'll post a patch.
> >
> 
> I don't think that using getTypeAllocSize() instead of
> getTypeStoreSize() to calculate clover::argument::size would be a
> satisfactory solution.  By doing that you'd redefine the API argument
> size exposed to the host for *all* argument types to be the
> device-dependent aligned size, which is definitely not what you want.

> AFAIK 3-element vectors are an exception because they are the only types
> that are defined to have a different API size from their actual usable
> size, so they probably deserve special handling in invocation.cpp (as
> you did in your first patch).  As the API size is target-independent I
> don't think that the fix belongs in Clang or LLVM, Clover is likely at
> fault.

The way I understood the ch 6.1.5 is that both API and OpenCL C 3
element vectors are required to be 4*sizeof(component). So a
sizeof(float3) == sizeof(cl_float3) == 16, and should be both host and
target independent. That's why clang (or more precisely libclc) looked
like a correct place.

I understand that target device can have stricter alignment rules, but I
don't see how it can have different type sizes (my reading of the specs
is that these are binding for the target as well).

I can resend the original patch with debug output replaced by a comment.

regards,
Jan

> 
> Thanks.
> 
> > regards,
> > Jan
> >
> >
> > -- 
> > Jan Vesely <jan.vesely at rutgers.edu>
> > _______________________________________________
> > mesa-dev mailing list
> > mesa-dev at lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/mesa-dev

-- 
Jan Vesely <jan.vesely at rutgers.edu>
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