Additional information:
As a rough estimate of how much speed this would cost on older hardware,
I previously measured beignet as 8-16x faster than pocl (but this will
obviously depend on hardware and application). However, beignet (on
hardware that can't use intel-opencl-icd) is limited to single precision
and OpenCL 1.2, so some OpenCL code won't run at all in beignet (e.g.
#877316).
beignet skips its tests if it can't find suitable GPU hardware (because
buildds/debci probably don't have it), so if you think you have a fix,
check whether the tests actually ran. There are some hints on enabling
the GPU in a chroot in README.source, but I'm not sure if they actually
work.