ARB_program_interface_query and shader_runner

Posted by Samuel Iglesias on September 25, 2015

Lately I have worked on ARB_shader_storage_buffer_object  extension implementation on Mesa, along with Iago (who has already explained how we implement it).

One of the features we implemented was adding support for buffer variables to the queries defined in ARB_program_interface_query. Those queries ended up being very useful to check another feature introduced by ARB_shader_storage_buffer_object: the new storage layout called std430.

I have developed basic tests for piglit, but Jordan Justen and Ilia Mirkin mentioned that Ian Romanick had worked in a comprehensive testing for uniform buffer objects presented at XDC2014.

Ian developed a stochastic search-based testing for uniform block layouts which generates shader_runner tests using a template in Mako that defines a series of uniform blocks with different layouts. Finally, shader_runner verifies some information through glGetActiveUniforms*() queries such as: the variable type, its offset inside the block, its array size (if any), if it is row major, etc... using "active uniform" command.

That was the kind of testing that I was looking for, so I cloned his repository and developed a modified version for shader storage blocks and std430.

During that process, I found that shader_runner was lacking support for the queries defined in ARB_program_interface_query extension. Yesterday, the patches were pushed to master branch of the piglit repository.

If you want to use this new command, the format  is the following:

verify program_interface_query GL_INTERFACE_TYPE_ENUM var_name GL_PROPS_ENUM integer

or, if we include the GL type enum:

verify program_interface_query GL_INTERFACE_TYPE_ENUM var_name GL_PROPS_ENUM GL_TYPE_ENUM

I have written an example to show how to use this command in a shader_runner test. This is just a snippet showing the usage of the new command:

link success

verify program_interface_query GL_BUFFER_VARIABLE SSBO1.s5_1[0].s1_4[1].s1_3.fv3[0] GL_TYPE GL_FLOAT_VEC4
verify program_interface_query GL_BUFFER_VARIABLE SSBO1.s5_1[0].s1_4[1].s1_3.fv3[0] GL_TOP_LEVEL_ARRAY_SIZE 4
verify program_interface_query GL_BUFFER_VARIABLE SSBO1.s5_1[0].s1_4[1].s1_3.fv3[0] GL_OFFSET 128
verify program_interface_query GL_BUFFER_VARIABLE SSBO1.s5_1[0].s1_4[0].s1_3.fv3[0] GL_OFFSET 48
verify program_interface_query GL_BUFFER_VARIABLE SSBO1.s5_1[0].s1_4[0].m34_1 GL_TYPE GL_FLOAT_MAT3x4
verify program_interface_query GL_BUFFER_VARIABLE SSBO1.s5_1[0].s1_4[1].m34_1 GL_OFFSET 80
verify program_interface_query GL_BUFFER_VARIABLE SSBO1.s5_1[0].s1_4[1].m34_1 GL_ARRAY_STRIDE 0
verify program_interface_query GL_BUFFER_VARIABLE SSBO1.m43_1 GL_IS_ROW_MAJOR 1
verify program_interface_query GL_PROGRAM_INPUT piglit_vertex GL_TYPE GL_FLOAT_VEC4
verify program_interface_query GL_PROGRAM_OUTPUT piglit_fragcolor GL_TYPE GL_FLOAT_VEC4

I hope you find them useful for your tests!