Mesh shader workgroups always have the same amount of subgroups.
When the API workgroup size is the same as the real workgroup
size, this is a small optimization (using a constant instead of
a shader arg).
When the API workgroup size is smaller than the real workgroup
size (eg. when the number of output vertices or primitves is
greater than the API workgroup size on RDNA 2), this fixes a
potential bug because num_subgroups would return the "real"
workgroup size instead of the API one.
Cc: mesa-stable
Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Qiang Yu <yuq825@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/37947>
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