On Fri, 15 May 2026 09:52:20 GMT, Ferenc Rakoczi <[email protected]> wrote:
>> An aarch64 implementation of the MontgomeryIntegerPolynomial256.mult() >> method and IntegerPolynomial.conditionalAssign(). Since 64-bit >> multiplication is not supported on Neon and manually performing this >> operation with 32-bit limbs is slower than with GPRs, a hybrid neon/gpr >> approach is used. Neon instructions are used to compute intermediate values >> used in the last two iterations of the main "loop", while the GPRs compute >> the first few iterations. At the method level this improves performance by >> ~9% and at the API level roughly 5%. >> >> >> >> --------- >> - [x] I confirm that I make this contribution in accordance with the >> [OpenJDK Interim AI Policy](https://openjdk.org/legal/ai). > > Ferenc Rakoczi has updated the pull request incrementally with one additional > commit since the last revision: > > Accepting more suggestions from Andrew Dinn. src/hotspot/cpu/aarch64/stubGenerator_aarch64.cpp line 7758: > 7756: __ lsr(tmp, lo, montMulP256Shift2); > 7757: __ orr(hi, hi, tmp); > 7758: __ andr(lo, lo, mask); Suggestion: // compute 104-bit (40 + 64) full product __ umulh(hi, a, b); __ mul(lo, a, b); // combine 40 + 12 bits into hi result __ lsl(hi, hi, montMulP256Shift1); __ lsr(tmp, lo, montMulP256Shift2); __ orr(hi, hi, tmp); // mask off 52 bits of lo result __ andr(lo, lo, mask); ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/30941#discussion_r3259892902
