The CSR for this issue is available for review at https://bugs.openjdk.java.net/browse/JDK-8202555 <https://bugs.openjdk.java.net/browse/JDK-8202555>. If you have a JBS user name you can add yourself as reviewer by editing the issue directly, assuming you concur with the content.
Brian > On Mar 8, 2019, at 8:56 AM, raffaello.giulie...@gmail.com wrote: > > On 2019-03-08 14:35, Andrew Haley wrote: >> Hi, >> >> On 3/7/19 7:16 PM, Raffaello Giulietti wrote: >> >>> a couple of weeks ago I tried to refactor the code assuming the >>> existence of unsignedMultiplyHigh() (either as some future intrinsic or >>> as a Java method) and a wider representations of g with either 127 or >>> 128 bits: >>> g = g1 2^64 + g0 >>> >>> with either >>> 2^63 <= g1 < 2^64 (128 bits) >>> >>> or >>> 2^62 <= g1 < 2^63 (127 bits) >>> >>> Unfortunately, the resulting code of rop() isn't any simpler. That's >>> because then an intermediate sum can overflow the 64 bits of a long. As >>> a consequence, there's need for more elaborate logic to determine >>> the carry and other slightly more complicated computations to assemble >>> the final result. All in all, the resulting code has more operations and >>> looks longer. >> >> Ah, I see. I agree, we still don't quite have the full set of operations >> that we need in Java, in particular a nice way of doing an add with carry. >> > > Yes. > > >> Thank you for the explanation. >> > > You're welcome. > > >>> In the meantime I got rid of the last division. There's no division at >>> all in the whole algorithm. >> >> Excellent. This is looking very good indeed. >> >
