[riscv-port] RFR: 8278644: riscv: Intrinsify mulAdd [v2]

[Fei Yang]

On Tue, 21 Dec 2021 09:06:25 GMT, Feilong Jiang <fjiang at openjdk.org> wrote:

>> BigInteger intrinsic: mulAdd intrinsic is missed in current vm. It should be implemented.
>> The JMH test of mulAdd intrinsic on the matched board shows that the performance can be improved by 0.69%~21.91% when the length of BigInteger changed from 1 to 5000, compared with that of C2.
>> JMH test: [MyBenchmark.java](https://bugs.openjdk.java.net/secure/attachment/97414/MyBenchmark.java)
>> 
>> Performed full jtreg test with qemu without new failures.
>> 
>> Results list as follows
>> | length | intrinsic(ops/ms) | no intrinsic(ops/ms) | intrinsic / no intrinsic |
>> | ------ | ------ | ------ | ------ | 
>> | 1 | 1643.111 | 1623.814 | 1.18% |
>> | 2 | 1597.927 | 1585.216 | 0.80% |
>> | 3 | 1542.249 | 1502.455 | 2.65% |
>> | 5 | 1533.371 | 1522.837 | 0.69% |
>> | 10 | 1377.683 | 1361.718 | 1.17% |
>> | 50 | 925.826 | 844.276 | 9.62% |
>> | 100 | 638.767 | 576.276 | 10.84% |
>> | 1000 | 99.870 | 84.796 | 17.78% |
>> | 2000 | 51.511 | 43.624 | 18.08% |
>> | 5000 | 18.017 | 14.779 | 21.91% |
>
> Feilong Jiang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   change the type of i in for loop to match the type of unroll

Looks good. Thanks.

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Marked as reviewed by fyang (Lead).

PR: https://git.openjdk.java.net/riscv-port/pull/36