Yep, Catalyst 14.4 still exposes the problem ... amplified
The render differs from the GPU implementation and also from the C++/SIMD implementation. It only happens with the AMD's OpenCL CPU implemention, your GPU implemention seems to be fine.
The "floor" problem is solved when "-cl-fast-relaxed-math" is not used though ( I bet it's a precision or optimization problem ) ... but the wall's z-fighting occurs even with the relaxed math disabled... and it completely differs from the GPU implementation anyways. Also, both Intel and NVIDIA implementions are working ok, so the problem seems to be related exclusively to your AMD CPU implementation ( maybe because I'm using an Intel CPU? )
By the way, I'm using W8.1 x64 ( also W7 SP1 x64 ), Cat.14.4, Radeon 7770-1Gb, Intel i7-2700K Sandy Bridge.