7.8. Function Multiversioning

7.8 Function Multiversioning

With the GNU C++ front end, for x86 targets, you may specify multiple versions of a function, where each function is specialized for a specific target feature. At runtime, the appropriate version of the function is automatically executed depending on the characteristics of the execution platform. Here is an example.

__attribute__ ((target ("default")))
int foo ()
{
  // The default version of foo.
  return 0;
}

__attribute__ ((target ("sse4.2")))
int foo ()
{
  // foo version for SSE4.2
  return 1;
}

__attribute__ ((target ("arch=atom")))
int foo ()
{
  // foo version for the Intel ATOM processor
  return 2;
}

__attribute__ ((target ("arch=amdfam10")))
int foo ()
{
  // foo version for the AMD Family 0x10 processors.
  return 3;
}

int main ()
{
  int (*p)() = &foo;
  assert ((*p) () == foo ());
  return 0;
}

In the abo