I believe Krejzi was right all along. I don't need llvm and elfutil for r600 GPU. I deleted llvm and recompiled Mesa with support for just r600, svga, and swrast. Then I compiled kernel 4.7.5 with extra firmware for just R600, but not Tahiti and Aruba. Everything works just fine. All of the glx errors are gone.
Code:
$ glxinfo|grep -i opengl
OpenGL vendor string: X.Org
OpenGL renderer string: Gallium 0.4 on AMD ARUBA (DRM 2.45.0 / 4.7.5)
OpenGL core profile version string: 4.1 (Core Profile) Mesa 12.0.3
OpenGL core profile shading language version string: 4.10
OpenGL core profile context flags: (none)
OpenGL core profile profile mask: core profile
OpenGL core profile extensions:
OpenGL version string: 3.0 Mesa 12.0.3
OpenGL shading language version string: 1.30
OpenGL context flags: (none)
OpenGL extensions:
OpenGL ES profile version string: OpenGL ES 3.0 Mesa 12.0.3
OpenGL ES profile shading language version string: OpenGL ES GLSL ES 3.00
OpenGL ES profile extensions:
Finally solved. Thanks Krejzi.