Convert 0x1234 to 0x11223344

Question

How do I expand the hexadecimal number 0x1234 to 0x11223344 in a high-performance way?

unsigned int c = 0x1234, b;
b = (c & 0xff) << 4 | c & 0xf |          


        

Answer 1

I wanted to add this link into the answer pool because I think it is extremely important when talking about optimization, to remember the hardware we are running on, as well as the technologies compiling our code for said platform.

Blog post Playing with the CPU pipeline is about looking into optimizing a set of code for the CPU pipelining. It actually shows an example of where he tries to simplify the math down to the fewest actual mathematical operations, yet it was FAR from the most optimal solution in terms of time. I have seen a couple of answers here speaking to that effect, and they may be correct, they may not. The only way to know is to actually measure the time from start to finish of your particular snippet of code, in comparison to others. Read this blog; it is EXTREMELY interesting.

I think I should mention that I am in this particular case not going to put ANY code up here unless I have truly tried multiple attempts, and actually gotten on that is particularly faster through multiple tries.