AMD OpenGL drivers claim GL_ARB_shader_image_load_store with no actual support
Core Profile
Compatibility Profile
imageAtomicAdd
OK
BROKEN
imageAtomicMin
OK
BROKEN
imageAtomicMax
OK
BROKEN
imageAtomicAnd
OK
BROKEN
imageAtomicOr
OK
BROKEN
imageAtomicXor
OK
BROKEN
imageAtomicExchange
OK
BROKEN
imageAtomicCompSwap
BROKEN
BROKEN
These results can be reproduced on all driver versions across Linux and Windows. The situation hasn't improved at all since the first drivers with OpenGL 4.2 "support" were released.
Arguably the most important function for modern shading techniques, imageAtomicCompSwap doesn't work on any combination of profile or platform.
Drivers making wrong claims about supported functionality is actually worse for application developers than if the functionality wasn't implemented at all, because programs end up relying on broken functionality advertised by the drivers.