As far as I know there is no support for inline assembly in OpenCL; however I would really like some kind of access to 32-bit (and 64-bit if possible) carry/borrow add and sub functions with carry/borrow in and out.

In the meantime, are there any efficient methods to performing such operations without many conditional tests or arithmetic operations?

Also, since there is no operator overloading in OpenCL, developing emulated basic data types (say 256 bit integers or floating-point numbers) is entirely possible but exceedingly cumbersome. Since 128 bit integers (long long) and floating-point numbers (quad) are reserved for possible future inclusion, how does Khronos plan to implement them?