v3dv: handle multisample rasterization with empty framebuffers
If the framebuffer has no attachments then multisample rasterization
is enabled based on the rasterizationSamples multisample state of
the pipelines. It should be noted that since we don't support
the variableMultisampleRate feature, all pipelines in the same
subpass must have matching number of samples.
V3D requires that we specifically setup our frames to enable
multisampling or not, and we do this when we create jobs inside
a subpass. Since we create the first job for a subpass as soon as
the subpas starts, this is problematic: if we don't have any
attachments, we don't won't enable MSAA at this point, but later
on we might bind an MSAA pipeline, since pipelines can be bound
at any point in the lifespan of a command buffer.
Here, we fix this by testing if the first draw call in a job uses
an MSAA pipeline but the job the was setup to not use MSAA, and in
that case we re-start the job with MSAA enabled.
We also take care of a corner case that seems to be tested by CTS
where a framebuffer with no attachments doesn't bind any pipelines
with MSAA enabled (so according to the Vulkan spec, multisample
rasterization must be disabled) but the fragment shader in use
reads gl_SampleID (which enables per-sample shading). This would
lead to enabling per-sample shading with single-sample rasterization,
which doesn't make sense and makes the simulator complain, so we just
disable per-sample shading in that case.
Fixes:
dEQP-VK.pipeline.multisample.mixed_count.*
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6766>
3 files changed
