[Mesa-dev] [PATCH v4 17/17] glsl linker: compare interface blocks during interstage linking

[Kenneth Graunke]

On 05/16/2013 05:44 PM, Jordan Justen wrote:
> Verify that interface blocks match when linking separate shader
> stages into a program.
>
> Fixes piglit glsl-1.50 tests:
> * linker/interface-blocks-vs-fs-member-count-mismatch.shader_test
> * linker/interface-blocks-vs-fs-member-order-mismatch.shader_test
>
> Signed-off-by: Jordan Justen <jordan.l.justen at intel.com>
> ---
>   src/glsl/interface_blocks.cpp |   47 +++++++++++++++++++++++++++++++++++++++--
>   src/glsl/interface_blocks.h   |    4 ++++
>   src/glsl/linker.cpp           |    6 ++++++
>   3 files changed, 55 insertions(+), 2 deletions(-)

I have a few annoying spec questions:

1. What happens if the producer has output interfaces not used by the 
next stage?  Is that legal (like unused varyings)?

For example,
    [vertex shader]
    out foo { vec4 a };
    out bar { int b };

    [fragment shader]
    in foo { vec4 a };
    // FS does not reference bar

2. What happens if the consumer has input interfaces not declared in the 
previous stage?  Is that legal?  If so, does it get populated with 
undefined values?

For example,
    [vertex shader]
    out foo { vec4 a };
    // VS does not declare/write bar

    [fragment shader]
    in foo { vec4 a };
    in bar { int b };

The text in the spec is really obnoxious...it's so hand-wavy and full of 
examples and prose...