Actually, I just discovered [Vyacheslav's post on this list][0]. Looks like my proposal has not much to offer, comparing to his.
Thanks anyway! [0]: https://www.mail-archive.com/es-discuss%40mozilla.org/msg27237.html On Wed, Jul 2, 2014 at 2:37 PM, Fedor Indutny <fe...@indutny.com> wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > Hello everyone! > > While working on bn.js, I have found one bottleneck in integer > multiplication > which could be solved with introduction of a new Math functions. > > In [multiply operation][0] the most expensive part is obviously an integer > multiplication. EcmaScript could operate with 51bit numbers without the > loose of > precision, but the whole thing requires compilers to translate SMIs (small > integers) into a floating point values and operate on them. > > Introduction of `Math.mulxHigh` and `Math.mulxLow` with a help of compiler > could > make this limitation go away. Namely, a compiler could coalesce these two > calls > into a one `mulx` instruction, making it possible to implement big numbers > with > a 32 bit limb. > > The code sample is following: > > var hi = Math.mulxHigh(a, b); // High 32 bits of the multiplication > result > var lo = Math.mulxLow(a, b); // Low 32 bits of the multiplication > result > > And this could be translated to a just: > > movx rax, rbx, rcx > > on IA32 platform. On the platforms that do not have a single instruction > for > this operation, the resulting code should still be faster, because it could > avoid `integer -> floating point -> integer` conversion. > > I'm open to any suggestions. What do you think? > > Thank you, > Fedor. > > [0]: > https://github.com/indutny/bn.js/blob/95e0623aaa637a3a6a87f9a7b30aafed758aa4eb/lib/bn.js#L590-L599 > > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1 > > iQIcBAEBAgAGBQJTs+A8AAoJEPsOEJWxeXmZ0O4P/2TmAjLCZ6HwKjPheaAXEXIB > tg3SbRyQNS/he/ZRs+0JkSePKVHlpgg/BBzlSJ4JGnFIEv2zYA/MfKzwrMGhkAXq > 1vYSUgm5sAwXZpmsJwEND6Kvb7sAPP19y2eKuJ/FwiHdkJXgEsT+Mz0w3nKwYd04 > 9g1FHTTn5Z+hnRP/9evGwUCV05cLQaD1VMnlzYfVvRHkGy3coEH0+5HtvSB/bnFA > mkTQV26bimlllIhrE4QWWRPGR3bFq9Ec5kQr10Gm9LGYLgL7D7fBaQNvc+EkTMxE > ELyabtrSwpRxfDlrXHZZPFM7vta9dYFnYnYpd95q904d94U7wG0H5WM6SA30cFdE > J40/IIo5DBbDIHcGxypOvIEjBJvvBFCdKXd8JVYm5BUGowRrNVdWDK0HuurrWYwc > fDVrx1mD45+HBwmtBcvYrN84hDkgyXnZgoxBqUCzL4EBK0bT7dnvZKG7yBP4gUE0 > UxptldK4MYSdcsczQcjVoDZ/crcgHMoW4vpK8t++Rpmqic0p786ijCjH3HMppyoO > LcPqGgWE2CyIm/VwS6omEoo5s9yYpDfpHuZ8ZnJp0/lD2s7DgQWtZsvveS4jGx4p > K5LrLUul8r6ydnkRLQCUmH23IwpoeA+NOZF06mIyMcObXrv8Gknp1WIA4/kt55Fs > xzciHPFWb/vavbGCEu+7 > =9xHZ > -----END PGP SIGNATURE----- >
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