Re: Why do call-clobbered local variables make the function not suitablefor tail call optimization?

[Jie Zhang <zhangjie at magima dot com dot cn>]

Hi Richard,

Richard Henderson wrote:

> On Wed, Jul 21, 2004 at 01:56:26PM +0800, Jie Zhang wrote:
>
> > Thanks. Then how about tail recursion optimization? Why is it also 
> > prevented by call-clobbered local variables?
>
> A similar argument.

I finally got one, which is similar to your example.

int *global;

int foo()
{
  int x;

  if (global != 0)
    {
      x = 321;
      return *global;
    }
  else
    {
      x = 123;
      global = &x;
      return foo ();
    }
}

int main()
{
  if (foo() != 123)
    abort ();
  return;
}


Thanks for your replies. Now I can understand tree-tailcall.c better. :-)


Regards
--
Jie