What is different about C++ math.h abs() compared to my abs()

Question

I am currently writing some glsl like vector math classes in C++, and I just implemented an abs() function like this:

template
static         


        

Answer 1

Your version of abs is inlined and can be computed once and the compiler can trivially know that the value returned isn't going to change, so it doesn't even need to call the function.

You really need to look at the generated assembly code (set a breakpoint, and open the "large" debugger view, this disassembly will be on the bottom left if memory serves), and then you can see what's going on.

You can find documentation on your processor online without too much trouble, it'll tell you what all of the instructions are so you can figure out what's happening. Alternatively, paste it here and we'll tell you. ;)