Same setup but with mesa built with LLVM support:

# ./piglit run -s all results/OpenGL_all_llvm
Skipping GL_ARB_gpu_shader_fp64 tests
[54211/54211] skip: 30608, pass: 20471, warn: 15, fail: 3044, crash: 73   
Thank you for running Piglit!                                          
Results have been written to /root/build/piglit/results/OpenGL_all_llvm

$ glxinfo | grep -i opengl
OpenGL vendor string: X.Org
OpenGL renderer string: AMD CAICOS (DRM 2.49.0 / 4.9.87-gentoo, LLVM 5.0.1)
OpenGL core profile version string: 3.2 (Core Profile) Mesa 18.0.0-rc4
OpenGL core profile shading language version string: 1.50
OpenGL core profile context flags: (none)
OpenGL core profile profile mask: core profile
OpenGL core profile extensions:
OpenGL version string: 3.0 Mesa 18.0.0-rc4
OpenGL shading language version string: 1.30
OpenGL context flags: (none)
OpenGL extensions:
OpenGL ES profile version string: OpenGL ES 3.1 Mesa 18.0.0-rc4
OpenGL ES profile shading language version string: OpenGL ES GLSL ES 3.10
OpenGL ES profile extensions: