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

There can be several things:

• are you sure the first call uses std::abs? It could just as well use the integer abs from C (either call std::abs explicitely, or have using std::abs;)

• the compiler might have intrinsic implementation of some float functions (eg. compile them directly into FPU instructions)

However, I'm surprised the compiler doesn't eliminate the loop altogether - since you don't do anything with any effect inside the loop, and at least in case of abs, the compiler should know there are no side-effects.