Re: [patch] tree-vrp.c: Avoid VR_ANTI_RANGE in a binary expression.

[Andrew Pinski <pinskia at physics dot uc dot edu>]

On Jun 22, 2005, at 11:21 AM, Diego Novillo wrote:

> On Tue, Jun 21, 2005 at 10:25:42AM -0400, Kazu Hirata wrote:
>
> > Tested on x86_64-pc-linux-gnu.  OK to apply?
> No.  ~[0,0] * ~[0,0] == ~[0,0].
>
> Your test needs to be less broad.  It will probably be sufficient
> to do this inside the handler for PLUS_EXPR.

It is also MINUS_EXPR too.
Wrong, this is also miscompiled as unsigned overflow is defined:
unsigned int f(unsigned char a, unsigned  char b)
{
  unsigned char c;
  if (a != 0)
   if (b != 0)
    {
     c = ((unsigned)a)*((unsigned)b);
     printf("c=%d\n", c);
     if (c!=0)
      abort();
    }
}

int main(void)
{
  f(0x80,0x80);
  return 0;
}

Thanks,
Andrew Pinski