sibcall-4.c

this is a gcc file, you can download it and learn its usetility, for further detail please look at t

/* Simple check that sibling calls are performed from a
   void non-leaf-function taking no arguments calling a function which
   is about the same as itself.

   Copyright (C) 2002 Free Software Foundation Inc.
   Contributed by Hans-Peter Nilsson  <[e-mail]>  */

/* { dg-do run { xfail arc-*-* avr-*-* c4x-*-* cris-*-* h8300-*-* i370-*-* i960-*-* ip2k-*-* m32r-*-* m68hc1?-*-* m681?-*-* m680*-*-* m68k-*-* mcore-*-* mips*-*-* mn10?00-*-* ns32k-*-* s390*-*-* xstormy16-*-* v850*-*-* vax-*-* xtensa-*-* } } */
/* { dg-options "-O2 -foptimize-sibling-calls" } */

/* The option -foptimize-sibling-calls is the default, but serves as
   marker.  This test is xfailed on targets without sibcall patterns
   (except targets where the test does not work due to the return address
   not saved on the regular stack).  */

static void recurser_void1 (void);
static void recurser_void2 (void);
extern void track (void);

int n = 0;
int main ()
{
  recurser_void1 ();
  exit (0);
}

/* The functions should get the same stack-frame, and best way to make it
   reasonably sure is to make them have the same contents (regarding the
   n tests).  */

static void
recurser_void1 (void)
{
  if (n == 0 || n == 7 || n == 8)
    track ();

  if (n == 10)
    return;
  n++;
  recurser_void2 ();
}

static void
recurser_void2 (void)
{
  if (n == 0 || n == 7 || n == 8)
    track ();

  if (n == 10)
    return;
  n++;
  recurser_void1 ();
}

void *trackpoint;

void
track ()
{
  char stackpos[1];

  if (n == 0)
    trackpoint = stackpos;
  else if ((n != 7 && n != 8) || trackpoint != stackpos)
    abort ();
}