[Libre-soc-dev] Loading Vulkan Driver

[Luke Kenneth Casson Leighton]

On Monday, August 24, 2020, Dave Airlie <airlied at gmail.com> wrote:

>
> amdgpu is completely scalar,


it is?? waah! that's new information to me.  does it even squash vec2/3/4,
predication and swizzle?

what about the upstream amdgpu LLVM-IR?  that still preserves vector
intrinsics, right?

i'm assuming that AMDVLK preserves vector intrinsics?

AMDVLK's associated LLVM port was what ended up upstream, is that right?

I think you will hit problems with vectorisation, because it's always
> been a problem for every effort in this area, but if the CPU design is
> such that everything can be vectorised and you never hit a scalar
> path,


that's the plan.  every single scalar POWER9 opcode with very few
exceptions (branch, trap) is vectorised.

and you workout how texture derivatives work early, it might be
> something prototype-able.


good advice to plan on texture opcodes.  thank you.


> thing, or bring up this architecture on an x86 chip and see it works
> at all.


that's the plan.  phase I.  run on x86, IBM POWER9, etc. first [whilst
still preserving vector intrinsics until as late as possible]

by the time phase I is complete we hope that Simon Moll and Robin Kruppe's
LLVM-IR Vector Intrinsics will have landed, at which point we can do an
experimental LLVM port which supports LibreSOC POWER9 vector augmentation,
swizzle, transcendentals and texturisation opcodes etc.

l.



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