[Mesa-dev] How to get uniform components used by uniform variables

[Juan A. Suarez Romero]

Hello.

I'm working on providing piglit with tests for the
GL_ARB_gpu_shader_fp64 extension[1].


One of the modifications it does is referring uniform variables:

"Modify Section 2.14.4, Uniform Variables, p. 89

(modify third paragraph, p. 90) ... uniform variable storage for vertex
shader.  A uniform matrix with single- or double-precision components
will consume no more than 4 * min(r,c) or 8 * min(r,c) uniform
components, respectively.  A scalar or vector uniform with double-
precision components will consume no more than 2<n> components, where
<n> is 1 for scalars, and the component count for vectors.  A link
error is generated ..."


So a float/int/bool consumes 1 UC (Uniform Component), and a double
consumes 2 UCs. A vec3 for instance will consume 3*1=3 UCs, and a
dvec3, 3*2=6 UCs.

The interesting part is about matrices: a mat3x2 won't consume more
than 4*min(3,2)=8 UCs (ideally would consume 1*3*2=6 UCs, but spec
allows a bit more), while a dmat3x2 will consume 8*min(3,2)=16 UCs
(again, ideally 2*3*2=12 UCs).

The question is, how to test this (if it is possible)? I didn't find
any way to know how many UCs an uniform variable is consuming, either
direct or indirectly.

Does any know if it is possible, and how to do it? I guess it should be
possible, otherwise I don't see the point of specifying something that
can be tested later.

Thanks in advance!


[1]https://www.opengl.org/registry/specs/ARB/gpu_shader_fp64.txt