[Pkg-opencl-devel] Bug#1059511: Bug#1059511: pocl: FTBFS on riscv64: testsuite fails: can't link double-float modules with soft-float modules

[Bo YU]

Hi,

On Thu, Jan 18, 2024 at 5:41 PM Andreas Beckmann <anbe at debian.org> wrote:
>
> On 18/01/2024 08.41, Bo YU wrote:
> > Obviously these tests failed was due to vectors missing from riscv64
> > now. This is expected I think.
> >
> > The result is aligned with pocl upstream support riscv64:
> >
> > ```
> > In this release we improved support for RISC-V CPUs. We tested PoCL on a Starfive VisionFive 2 using a Ubuntu 23.10 preinstalled image. With LLVM 17 and GCC 13.2, 98% tests pass (only 4 tests fail out of 253).
>
> If these tests are expected to fail, they should be annotated as such
> for riscv64 (see e.g. handing of kernel/test_printf_vectors in
> tests/kernel/CMakeLists.txt). Is there an upstream bug about these tests
> failing on risc-v?

I have report the issue to upstream and got their confirmation:
https://github.com/pocl/pocl/issues/1394

>
> printf is a mess on most architectures (even or especially also x86)
> since the ABI for passing the variadic parameters is not well defined,
> especially when it comes to OpenCL vector types.
>
> > So I suspect the `LLC_HOST_CPU='` was overriden by `GENERIC` then the
> > ABI was different. I will look at this more deeper.
>
> GENERIC is a Debian specific patch to build for the LLVM default target
> (i.e. without specifying -march=$whatever), s.t. the generated code
> targets the riscv64 baseline (like all code in Debian binary packages).
> (Assuming llvm targets the same baseline cpu architecture as gcc, which
> unfortunately is not true for all Debian architectures.)
> (By default upstream pocl wants to build for the native CPU which is a
> no-go for distributing binaries. In order to fully utilize capabilities
> for more modern CPUs (e.g. wider SIMD registers), pocl has a distro mode
> where the bitcode libraries are provided for multiple targets and the
> best one for the local CPU is selected at runtime. But first we should
> get a baseline build for risc-v before we look into optimizing it (i.e.
> supporting separately both CPUs without and with vector unit).

Thanks.

So we need to enable to select the best one for local CPU when runtime
for riscv64 here. I looked at the patch:
https://salsa.debian.org/opencl-team/pocl/-/blob/main/debian/patches/generic-cpu.patch?ref_type=heads
But I am not sure how to enable this.

The baseline of riscv64 port here is here:
```
The Debian port uses RV64GC as the hardware baseline and the lp64d ABI
(the default ABI for RV64G systems)
```
https://wiki.debian.org/RISC-V#Hardware_baseline_and_ABI_choice

Is this enough information? Please let me know of any issues or I can
do some experiment about this.

BR,
Bo
>
> Andreas
>
> PS: I'll look into switching pocl to llvm-16 now