[Bug middle-end/112639] New: Incorrect handling of __builtin_c[lt]zg argument side-effects

[jakub at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112639

            Bug ID: 112639
           Summary: Incorrect handling of __builtin_c[lt]zg argument
                    side-effects
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jakub at gcc dot gnu.org
  Target Milestone: ---

unsigned long long b = 0;

int
foo (void)
{
  return __builtin_clzg (b++, __SIZEOF_LONG__ * __CHAR_BIT__);
}

int
bar (void)
{
  return __builtin_ctzg (b++, __SIZEOF_LONG__ * __CHAR_BIT__);
}

int
main ()
{
  if (foo () != __SIZEOF_LONG__ * __CHAR_BIT__ || b != 1)
    __builtin_abort ();
  if (foo () != __SIZEOF_LONG__ * __CHAR_BIT__ - 1 || b != 2)
    __builtin_abort ();
  if (foo () != __SIZEOF_LONG__ * __CHAR_BIT__ - 2 || b != 3)
    __builtin_abort ();
  b = 0;
  if (bar () != __SIZEOF_LONG__ * __CHAR_BIT__ || b != 1)
    __builtin_abort ();
  if (bar () != 0 || b != 2)
    __builtin_abort ();
  if (bar () != 1 || b != 3)
    __builtin_abort ();
}

is miscompiled.