RFR(M): 8145913: PPC64: add Montgomery multiply intrinsic

[Andrew Haley]

Hi,

On 23/12/15 15:42, Doerr, Martin wrote:

> I've ported the Montgomery multiplication from x86.
> 
> The webrev is here:
> http://cr.openjdk.java.net/~mdoerr/8145913_ppc_montgomery/webrev.00/
> 
> It only touches PPC64 files. It also contains some early feedback from Götz and some additional PPC64 cleanup.
> 
> Please review.

Looks good.

This needs work:

+// The threshold at which squaring is advantageous was determined
+// experimentally on an i7-3930K (Ivy Bridge) CPU @ 3.5GHz.
+#define MONTGOMERY_SQUARING_THRESHOLD 64

I'm sure it won't take long to find an appropriate threshold for
the CPU you most care about.  Hey, 64 might be best for you too,
but at least you get to insert the name of a PowerPC in that
comment.

Andrew.