Re: [patches] Re: teach simplify_rtx to simplify unordered compares

[Jan Hubicka <jh at suse dot cz>]

> >>>>> Jan Hubicka writes:
> 
> >> This  can be removed - or change the condition below.
>  > It can not be, since the code in between may cause exception in the NAN case on
>  > architectures not masking them by default and return wia longjmp.
> I see:
> 
> But in that case the can look like (the extra args->unordered = 1 is
> not needed) :
> 
>    args->unordered = 1;
>  
>    REAL_VALUE_FROM_CONST_DOUBLE (d0, args->op0);
>    REAL_VALUE_FROM_CONST_DOUBLE (d1, args->op1);
>    if (!REAL_VALUE_ISNAN (d0)
>        && REAL_VALUE_ISNAN (d1))
>      args->unordered = 0;
> 
> or even (if it's unordered, args->equal, args->op0lt and args->ob1lt
> should all be false!):
>    args->unordered = 1;
>  
>    REAL_VALUE_FROM_CONST_DOUBLE (d0, args->op0);
>    REAL_VALUE_FROM_CONST_DOUBLE (d1, args->op1);
>    if (REAL_VALUE_ISNAN (d0)
>        || REAL_VALUE_ISNAN (d1))
>      return;
>    else
>      args->unordered = 0;
OK, this change is surely possible.
> 
> Btw. what happens if d0 or d1 is an infinity?  In that case you also
I don't have IEEE specs (they do want money) but my Athlon claims even
the Inf versus Inf comparison to be ordered.

> have an unordered comparison - therefore change the if to:
>    if (!REAL_VALUE_ISNAN (d0) && !REAL_VALUE_ISNAN (d1)
>        && !REAL_VALUE_ISINF (d0) && !REAL_VALUE_ISINF (d1))
> 
> Andreas
> -- 
>  Andreas Jaeger
>   SuSE Labs aj@suse.de
>    private aj@arthur.inka.de
>     http://www.suse.de/~aj