linker: Accurately track gl_uniform_block::stageref

linker: Accurately track gl_uniform_block::stageref

As the linked per-stage shaders are processed, mark any block that has a
field that is accessed as referenced.  When combining all the linked
shaders, combine the per-stage stageref masks.

This fixes a number of GLES CTS tests:

    ES31-CTS.core.geometry_shader.program_resource.program_resource
    ES32-CTS.core.geometry_shader.program_resource.program_resource
    ESEXT-CTS.geometry_shader.program_resource.program_resource
    piglit.gl45-cts.geometry_shader.program_resource.program_resource

However, it makes quite a few more fail:

    ES31-CTS.functional.program_interface_query.buffer_variable.random.6
    ES31-CTS.functional.program_interface_query.buffer_variable.referenced_by.compute.unnamed_block.float
    ES31-CTS.functional.program_interface_query.buffer_variable.referenced_by.separable_fragment.unnamed_block.float
    ES31-CTS.functional.program_interface_query.buffer_variable.referenced_by.vertex_fragment_only_fragment.unnamed_block.float
    ES31-CTS.functional.program_interface_query.buffer_variable.referenced_by.vertex_fragment.unnamed_block.float
    ES31-CTS.functional.program_interface_query.buffer_variable.referenced_by.vertex_geo_fragment_only_fragment.unnamed_block.float
    ES31-CTS.functional.program_interface_query.buffer_variable.referenced_by.vertex_geo_fragment.unnamed_block.float
    ES31-CTS.functional.program_interface_query.buffer_variable.referenced_by.vertex_tess_fragment_only_fragment.unnamed_block.float
    ES31-CTS.functional.program_interface_query.buffer_variable.referenced_by.vertex_tess_fragment.unnamed_block.float
    ES31-CTS.functional.program_interface_query.buffer_variable.referenced_by.vertex_tess_geo_fragment_only_fragment.unnamed_block.float
    ES31-CTS.functional.program_interface_query.buffer_variable.referenced_by.vertex_tess_geo_fragment.unnamed_block.float
    ES32-CTS.functional.program_interface_query.buffer_variable.random.6
    ES32-CTS.functional.program_interface_query.buffer_variable.referenced_by.compute.unnamed_block.float
    ES32-CTS.functional.program_interface_query.buffer_variable.referenced_by.separable_fragment.unnamed_block.float
    ES32-CTS.functional.program_interface_query.buffer_variable.referenced_by.vertex_fragment_only_fragment.unnamed_block.float
    ES32-CTS.functional.program_interface_query.buffer_variable.referenced_by.vertex_fragment.unnamed_block.float
    ES32-CTS.functional.program_interface_query.buffer_variable.referenced_by.vertex_geo_fragment_only_fragment.unnamed_block.float
    ES32-CTS.functional.program_interface_query.buffer_variable.referenced_by.vertex_geo_fragment.unnamed_block.float
    ES32-CTS.functional.program_interface_query.buffer_variable.referenced_by.vertex_tess_fragment_only_fragment.unnamed_block.float
    ES32-CTS.functional.program_interface_query.buffer_variable.referenced_by.vertex_tess_fragment.unnamed_block.float
    ES32-CTS.functional.program_interface_query.buffer_variable.referenced_by.vertex_tess_geo_fragment_only_fragment.unnamed_block.float
    ES32-CTS.functional.program_interface_query.buffer_variable.referenced_by.vertex_tess_geo_fragment.unnamed_block.float

I have diagnosed the failures, but I'm not sure whether we or the
tests are wrong.  After optimizations are applied, all of the tests
are of the form:

    buffer X {
        float f;
    } x;

    void main()
    {
        x.f = x.f;
    }

The test then queries that x is referenced by that shader stage.  We
eliminate the assignment of x.f to itself, and that removes the last
reference to x.  We report that x is not referenced, and the test fails.
I do not know whether or not we are allowed to eliminate that assignment
of x.f to itself.

After discussions with the OpenGL ES group in Khronos, we believe that
Mesa's behavior is correct.  I will provide patches to the CTS tests
to Khronos.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>