[libre-riscv-dev] porting AMDVLK to the Libre RISC-V 3D GPU: NLNet EUR 50, 000 Grant application

Jacob Lifshay programmerjake at gmail.com
Thu Sep 26 03:13:37 BST 2019

On Wed, Sep 25, 2019 at 9:44 AM Luke Kenneth Casson Leighton
<lkcl at lkcl.net> wrote:
> On Wed, Sep 25, 2019 at 4:03 PM Michael Pham <pham.michael.98 at gmail.com> wrote:
> > In the end though, since you are turning the AMD driver into a Libre
> > RISC-V version, it might not even matter. But the point of me bringing
> > this up is that instead of porting AMDVLK, RADV might be a better base
> > to start from. Since Jacob is a graphics expert though, he'll have
> > better comments than mine (once he gets back).
> yehyeh.  it's not about the performance of RADV or AMDVLK, at the
> assembly-level or what-goes-on-the-screen level, it's about whether
> the SPIR-V to LLVM-IR code preserves the intrinsics and vectorisation
> semantics that we need for the SV Vector Engine.

Most of my concerns were addressed in the previous emails, though I
did want to point out that the part we would be doing the vast
majority of the work on is LLVM itself.
I am not completely sure about AMDVLK, but I know that RADV uses
upstream LLVM as the shader compiler backend.

If we were to base it off of one of AMDVLK or RADV, I'd pick RADV,
because we can then benefit from all the work that Mesa (not just AMD)
has put into NIR, where they do graphics-specific optimizations before
handing off the code to LLVM.

Jacob Lifshay

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