Ben Sander of AMD and  Chien-Ping Lu MediaTek HSA Foundation Working group leader for HSA Programer Reference Manual pen a nice article on HSAIL and HSA technology
 
“Power efficiency has emerged as a primary design goal for modern silicon chips.  Accelerators such as GPUs have well-known advantages in compute density per-watt and per-mm^2 – note for example that the systems at the top of the latest Green500 (http://www.green500.org/) and Top500 (http://www.top500.org/) lists are now based on heterogeneous designs.
However, these systems have traditionally been difficult to program, due to two challenges.  First, many accelerators support only dedicated address spaces that require cumbersome copy operations and prevent the use of pointer-based data structures on both the accelerator and the host processor.   Second, accelerator programming has traditionally required a specialized language such as OpenCL™ or CUDA™.  Some of these specialized languages are only supported by a single hardware vendor, which further constrains their adoption.
An intermediate language called HSAIL is helping to address some of the challenges. One of the benefits of HSAIL is its portability across multiple vendor products.  Compilers that generate HSAIL can be assured that the resulting code will be able to run on a wide variety of target platforms. HSAIL also provides existing programming languages with an efficient parallel intermediate language that runs on a wide variety of hardware.  This provides the underlying infrastructure and brings the benefits of heterogeneous computing to existing, popular programming models such as Java™, OpenMP™, C++, and more”. ………..  read more at this link bellow
http://www.computer.org/portal/web/computingnow/software%20engineering/content?g=53319&type=article&urlTitle=hsail%3A-write-once-run-everywhere-for-heterogenous-systems