gcc/testsuite/gcc.dg/builtin-arith-overflow-1.c

/* { dg-do run } */
/* { dg-options "-O2 -fdump-tree-optimized -g" } */

/* SUB_OVERFLOW should be folded into unsigned subtraction,
   because ovf is never used.  */
__attribute__((noinline, noclone)) int
fn1 (int x, unsigned int y)
{
  int res;
  int ovf = __builtin_sub_overflow (x, y, &res);
  int res2 = res;
  int res3 = res2 - 2;
  (void) ovf;
  return res;
}

/* MUL_OVERFLOW should be folded into unsigned multiplication,
   because ovf is never used.  */
__attribute__((noinline, noclone)) int
fn2 (signed char x, long int y)
{
  short int res;
  int ovf = __builtin_mul_overflow (x, y, &res);
  int res2 = res;
  int res3 = res2 - 2;
  (void) ovf;
  return res;
}

#if __SIZEOF_INT__ > __SIZEOF_SHORT__ && __SIZEOF_INT__ > 1
/* ADD_OVERFLOW should be folded into unsigned addition,
   because it never overflows.  */
__attribute__((noinline, noclone)) int
fn3 (signed char x, unsigned short y, int *ovf)
{
  int res;
  *ovf = __builtin_add_overflow (x, y, &res);
  return res;
}
#endif

/* MUL_OVERFLOW should be folded into unsigned multiplication,
   because it never overflows.  */
__attribute__((noinline, noclone)) long int
fn4 (long int x, long int y, int *ovf)
{
  long int res;
  x &= 65535;
  y = (y & 65535) - 32768;
  *ovf = __builtin_mul_overflow (x, y, &res);
  return res;
}

#if __SIZEOF_INT__ > 1
/* MUL_OVERFLOW should be folded into unsigned multiplication,
   because it always overflows.  */
__attribute__((noinline, noclone)) signed char
fn5 (long int x, long int y, int *ovf)
{
  signed char res;
  x = (x & 63) + (__SCHAR_MAX__ / 4);
  y = (y & 3) + 5;
  *ovf = __builtin_mul_overflow (x, y, &res);
  return res;
}
#endif

/* ADD_OVERFLOW should be folded into unsigned additrion,
   because it never overflows.  */
__attribute__((noinline, noclone)) unsigned char
fn6 (unsigned char x, unsigned char y, int *ovf)
{
  unsigned char res;
  x = (x & 63) + ((unsigned char) ~0 - 66);
  y = (y & 3);
  *ovf = __builtin_add_overflow (x, y, &res);
  return res;
}

/* ADD_OVERFLOW should be folded into unsigned additrion,
   because it always overflows.  */
__attribute__((noinline, noclone)) unsigned char
fn7 (unsigned char x, unsigned char y, int *ovf)
{
  unsigned char res;
  x = (x & 15) + ((unsigned char) ~0 - 15);
  y = (y & 3) + 16;
  *ovf = __builtin_add_overflow (x, y, &res);
  return res;
}

int
main ()
{
  int ovf;
  if (fn1 (-10, __INT_MAX__) != (int) (-10U - __INT_MAX__)
      || fn2 (0, 0) != 0
      || fn2 (32, 16383) != (short int) 524256ULL)
    __builtin_abort ();
#if __SIZEOF_INT__ > __SIZEOF_SHORT__ && __SIZEOF_INT__ > 1
  if (fn3 (__SCHAR_MAX__, (unsigned short) ~0, &ovf) != (int) (__SCHAR_MAX__ + (unsigned short) ~0)
      || ovf
      || fn3 (-__SCHAR_MAX__ - 1, 0, &ovf) != (int) (-__SCHAR_MAX__ - 1)
      || ovf)
    __builtin_abort ();
#endif
  if (fn4 (65535, 0, &ovf) != 65535L * -32768 || ovf)
    __builtin_abort ();
#if __SIZEOF_INT__ > 1
  if (fn5 (0, 0, &ovf) != (signed char) (__SCHAR_MAX__ / 4 * 5)
      || !ovf
      || fn5 (63, 3, &ovf) != (signed char) ((__SCHAR_MAX__ / 4 + 63) * 8)
      || !ovf)
    __builtin_abort ();
#endif
  if (fn6 (0, 0, &ovf) != (unsigned char) ~0 - 66
      || ovf
      || fn6 (63, 3, &ovf) != (unsigned char) ~0
      || ovf)
    __builtin_abort ();
  if (fn7 (0, 0, &ovf) != 0
      || !ovf
      || fn7 (63, 3, &ovf) != 18
      || !ovf)
    __builtin_abort ();
  return 0;
}

/* { dg-final { scan-tree-dump-not "ADD_OVERFLOW" "optimized" } } */
/* { dg-final { scan-tree-dump-not "SUB_OVERFLOW" "optimized" } } */
/* { dg-final { scan-tree-dump-not "MUL_OVERFLOW" "optimized" } } */