CODEWITHSUNDEEP
opencl
Litherum
Litherum

Reputation: 23364

OpenCL extensions with Apple's openclc

I'm interested in using an optional extension to OpenCL which adds certain functions to the OpenCL language (in particular, cl_khr_gl_msaa_sharing). I'm using Apple's openclc to compile my OpenCL sources at build-time, however, openclc fails to compile my source (see below) because of calls to these new functions. The machine I'm running on does, indeed, support the extensions, and if I use clCreateProgramWithSource() and clBuildProgram() at runtime, everything works great.

Obviously, any build-time tool can't know which extensions are supported at run-time. However, I'd like to be able to compile my source at build-time assuming the extension exists, then at run-time query for the presence for the extension and degrade gracefully if the extension isn't present. Is there a mechanism for doing anything like this?

The top answer to OpenCL half4 type Apple OS X suggests using preprocessor defines inside the OpenCL program to detect extensions, but that won't help me as those defines are evaluated at build-time.

The particular build-time compiler error is this: error: target does not support depth and MSAA textures

Upvotes: 2

Views: 330

Answers (1)

Michael
Michael

Reputation: 26

I had a similar problem; I wanted the compiler to assume that the extension cl_khr_fp64 existed so I could use the boilerplate code

#ifdef cl_khr_fp64
    #pragma OPENCL EXTENSION cl_khr_fp64 : enable
#elif defined(cl_amd_fp64)
    #pragma OPENCL EXTENSION cl_amd_fp64 : enable
#else
    #error "Double precision floating point not supported by OpenCL implementation."
#endif

and have it compile as if double precision was available.

The solution (as of XCode 6.3.1) was to select Target > Build Settings > OpenCL - Preprocessing, and add cl_khr_fp64 to the OPENCL_PREPROCESSOR_DEFINITIONS section.

The code then compiled without complaining within XCode, assuming there were no syntax errors in my source code (which is what I wanted to check).

Upvotes: 1

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