RFR[15] JDK-8243114: Implement montgomery{Multiply, Square}intrinsics on Windows

[Sean Mullan]

Cross-posting to hotspot-dev for additional review since the code 
changes are in hotspot.

--Sean

On 5/21/20 1:24 PM, Simon Tooke wrote:
> Hello,
> 
> I'd like to request a review for:
> 
> JBS: https://bugs.openjdk.java.net/browse/JDK-8243114
> 
> Webrev: http://cr.openjdk.java.net/~stooke/webrevs/jdk-8243114-jdk/00/00/
> 
> This change implements the given intrinsics on Windows.
> 
> The Windows toolchain has no 128 bit integer types, and no inline asm 
> (on x64 and Arm).  In addition, 'long' is 4 bytes, not 8, as it is with 
> gcc.  This patch had to change some of the linux implementation to 
> account for these limitations.
> 
> My gratitude for Andrew Haley for doing the heavy lifting at the core of 
> this patch.
> 
> The patch, if accepted, will be offered to 11u as a potential backport. 
> The changes apply cleanly modulo some line number changes.
> 
> As for the speedup, this test case:
> 
> BigInteger base = BigInteger.ONE.shiftLeft(1024);
> long count = LongStream.rangeClosed(2, 100_000)
>      .mapToObj(n -> BigInteger.valueOf(n).add(base))
>      .filter(i -> i.isProbablePrime(50))
>      .count();
> 
> goes from 1 minute 20 seconds down to about 35 seconds om my VM, over 
> multiple runs.  As is the case on other platforms where the intrinsics 
> are supported, they will be enabled by default on Windows.
> 
> Thank you for your time,
> 
> -Simon Tooke
> 
> 
> Principle Software Engineer,
> 
> Red Hat Canada
> 
> 
>