How to do unsigned saturating addition in C?

Question

What is the best (cleanest, most efficient) way to write saturating addition in C?

The function or macro should add two unsigned inputs (need both 16- and 32-bit ver

Answer 1

Saturation arithmetic is not standard for C, but it's often implemented via compiler intrinsics, so the most efficient way will not be the cleanest. You must add #ifdef blocks to select the proper way. MSalters's answer is the fastest for x86 architecture. For ARM you need to use __qadd16 function (ARM compiler) of _arm_qadd16 (Microsoft Visual Studio) for 16 bit version and __qadd for 32-bit version. They'll be automatically translated to one ARM instruction.

Links:

• __qadd16
• _arm_qadd16
• __qadd