[Bug analyzer/108968] fanalyzer false positive with the uninitalised-ness of the stack pointer

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108968

--- Comment #16 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Minimized version of attachment 54572:

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
struct cpu_info {
  /* [...snip...] */
  struct vcpu *current_vcpu;
  /* [...snip...] */
};

struct vcpu
{
  /* [...snip...] */
  struct domain *domain;
  /* [...snip...] */
};

static __inline__ struct cpu_info *get_cpu_info_from_stack(unsigned long sp)
{
  return (struct cpu_info *)((sp | ((((1L) << 12) << 3) - 1)) + 1) - 1;
}

static __inline__ struct cpu_info *get_cpu_info(void)
{
  register unsigned long sp asm("rsp");
  return get_cpu_info_from_stack(sp);
}

void foo(char *other)
{
  char *ptr = ((void*)0);
  if ( ((get_cpu_info()->current_vcpu))->domain )
    ptr = other;
  asm volatile ("cmc");
  if ( ((get_cpu_info()->current_vcpu))->domain )
    ptr[0] = ~ptr[0];
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~