x == Integer.MIN_VALUE should be faster than x == -x as it's a cmp against
a constant whereas the latter requires negating x (that's a dependency
too), tying up a register to store the negation, and then doing the cmp.
Sent from my phone
On Feb 3, 2012 12:53 PM, "Eamonn McManus" <eam...@mcmanus.net> wrote:
> My initial remarks:
>
> In negateExact, the condition x == -x should be faster to evaluate than x
> == Integer.MIN_VALUE and reflects the intent just as well.
>
> In addExact and subtractExact, I would be inclined to implement the int
> versions using long arithmetic, like this:
>
> long lr = x + y;
> int r = (int) lr;
> if (r == lr) {
> return r;
> } else {
> throw...
> }
>
> I would use this technique of cast-and-compare in the int multiplyExact
> instead of comparing against MIN_VALUE and MAX_VALUE, and especially in
> toIntExact(long).
>
> I agree with Stephen Colebourne that brief implementation comments would be
> useful. But I disagree with his proposed further methods in Math
> (increment, decrement, int+long variants), which I don't think would pull
> their weight.
>
> Éamonn
>
>
> On 2 February 2012 12:15, Roger Riggs <roger.ri...@oracle.com> wrote:
>
> > There is a need for arithmetic operations that throw exceptions
> > when the results overflow the representation of int or long.
> >
> > The CR is 6708398: Support integer overflow <http://bugs.sun.com/**
> > bugdatabase/view_bug.do?bug_**id=6708398<
> http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6708398>
> > >
> >
> > Please review this webrev <http://cr.openjdk.java.net/%**
> > 7Erriggs/CR6708398/webrev/<
> http://cr.openjdk.java.net/%7Erriggs/CR6708398/webrev/>>
> > to add static methods in java.lang.Math
> > to support addExact(), subtractExact(), negateExact(), multiplyExact(),
> > and toIntExact() for int and long primitive types.
> >
> > Thanks, Roger Riggs
> >
>
