Can I make my compiler use fast-math on a per-function basis?

Question

Suppose I have

template  void foo(float* data, size_t length);

and I want to compile one instantiation with

Answer 1

In GCC you can declare functions like following:

__attribute__((optimize("-ffast-math")))
double
myfunc(double val)
{
    return val / 2;
}

This is GCC-only feature.

See working example here -> https://gcc.gnu.org/ml/gcc/2009-10/msg00385.html

It seems that GCC not verifies optimize() arguments. So typos like "-ffast-match" will be silently ignored.