OpenGLCompute backend isn't being tested

[steven-johnson]

In Issue #5475 we decided to remove OpenGL but keep OpenGLCompute; AFAICT, we don't do any testing at all on the OpenGLCompute backend. The only thing in our code that appears to explicitly test it is apps/openglcompute, which is Android-specific (and hasn't been built in ~years). If we intend to keep this backend, we need to add some level of testing for it on the buildbots.

[shoaibkamil]

Agreed. Would it be simplest to turn this on for Linux testing? I realize those buildbots are pretty overtaxed, but I think testing for an additional backend isn't too bad (not like testing against an additional version of LLVM).

[steven-johnson]

Agreed. I'll enable that today and see how badly broken we are (as I assume we must be if we haven't been testing).

[steven-johnson]

Enabled it and I'm seeing LLVM errors of the form "Duplicate option categories" -- IIRC this is related to having multiple LLVM libraries in the open symbol space (i.e., one inside the driver, plus the one inside Halide)?

(This is on a Linux box with Nvidia hw + drivers)

[shoaibkamil]

Yes, that does indeed seem like the same issue. I worked around it in Makefile builds by setting the environment variable WITH_LLVM_INSIDE_SHARED_LIBHALIDE= before building, but of course this is NOT a long-term solution and requires carefully setting LD_LIBRARY_PATHs.

[steven-johnson]

See: #4651