It is not the same C, it is a dialect full of extensions, and it only applies to OpenCL, which it was one of the reasons why it failed and forced Khronos to come up with SPIR, playing catch up the polyglot PTX environmnent of CUDA.
OpenCL 3.0 is basically OpenCL 1.2, which is OpenCL before SPIR was introduced.
OpenCL 3.0 is basically OpenCL 1.2, which is OpenCL before SPIR was introduced.