On Wed, Sep 4, 2024 at 8:32 PM Jeff Law <j...@ventanamicro.com> wrote:
> On 9/2/24 2:01 PM, Raphael Moreira Zinsly wrote:
> ...
> > +      bool bit31 = (hival & 0x80000000) != 0;
> > +      int trailing_shift = ctz_hwi (loval) - ctz_hwi (hival);
> > +      int leading_shift = clz_hwi (loval) - clz_hwi (hival);
> > +      int shiftval = 0;
> > +
> > +      /* Adjust the shift into the high half accordingly.  */
> > +      if ((trailing_shift > 0 && hival == (loval >> trailing_shift))
> > +       || (trailing_shift < 0 && hival == (loval << trailing_shift)))
> > +     shiftval = 32 - trailing_shift;
> > +      else if ((leading_shift < 0 && hival == (loval >> leading_shift))
> > +             || (leading_shift > 0 && hival == (loval << leading_shift)))
> Don't these trigger undefined behavior when tailing_shift or
> leading_shift is < 0?  We shouldn't ever generate negative shift counts.

The value of trailing/leading_shift is added to 32, we will never have
negative shift counts.



--
Raphael Moreira Zinsly

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