v3dv: implement vkCmdDispatchBase

This was added with VK_KHR_device_group and allows users to specify
a base offset that will be automatically added to gl_WorkGroupID.

Unfortunately, V3D doesn't support this natively, so we need to add
the base to the workgroup id generated by hardware manually. For this,
we inject add instructions that source from a QUNIFORM that will
retrieve the actual dispatch base from the compute job when it is
dispatched.

Since a compute shader can be dispatched with CmdDispatch and/or
CmdDispatchBase, we always need to add these additional add
instructions and use a base of (0,0,0) for regular dispatches.
Since we don't support any version of OpenGL with this dispatch
base functionality we can avoid the extra instructions there.

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11037>

src/broadcom/compiler/v3d_compiler.h

@@ -299,6 +299,11 @@ enum quniform_contents {
          */
         QUNIFORM_NUM_WORK_GROUPS,
 
+        /* Base workgroup offset passed to vkCmdDispatchBase in the dimension
+         * selected by the data value.
+         */
+        QUNIFORM_WORK_GROUP_BASE,
+
         /**
          * Returns the the offset of the scratch buffer for register spilling.
          */