SPIR is the Standard Portable Intermediate Representation that serves as a standardized, cross-platform IR for OpenCL. SPIR is based on the LLVM IR and the 2.0 provisional specification brings support for the portable encoding of OpenCL 2.0 device programs.
The SPIR 2.0 brings support for a generic address space, device-side kernel enqueue, C++11 atomics, and support for pipes. Besides the SPIR specification, Khronos also publishes a modified version of LLVM's Clang to generate SPIR from OpenCL C, a SPIR module verifier, and a few other pieces of software. SPIR 2.0 is based on LLVM/Clang 3.4.
More details on SPIR 2.0 via the Khronos announcement.