RFR: 8321003: RISC-V: C2 MulReductionVI [v7]

[Hamlin Li]

> Hi,
> Can you help to review this patch to implement MulReductionVI/MulReductionVL/MulReductionVF/MulReductionVD?
> This optimization is mainly for the vector API.
> On riscv, there is no straightforward instructions to do it, but we can do it with a reduction tree, which could reduce the time complexity to lg(N).
> 
> 
> Thanks
> 
> ## Test
> 
> ### jtreg
> test/jdk/jdk/incubator/vector/
> 
> ### Performance
> 
> run on bananapi
> 
> master vs patch
> <google-sheets-html-origin style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); font-style: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none;">
> Benchmark | (size) | Mode | Cnt | Score - master | Error - patch | Score - patch | Error - patch | Units | Improvement
> -- | -- | -- | -- | -- | -- | -- | -- | -- | --
> ByteMaxVector.MULLanes | 1024 | avgt | 10 | 11170.052 | 499.676 | 1294.424 | 8.346 | ns/op | 88.40%
> ByteMaxVector.MULMaskedLanes | 1024 | avgt | 10 | 12514.587 | 55.06 | 1413.028 | 0.259 | ns/op | 88.70%
> DoubleMaxVector.MULLanes | 1024 | avgt | 10 | 57672.51 | 1750.417 | 4775.633 | 1.454 | ns/op | 91.70%
> DoubleMaxVector.MULMaskedLanes | 1024 | avgt | 10 | 63656.523 | 1063.048 | 5899.259 | 1.692 | ns/op | 90.70%
> FloatMaxVector.MULLanes | 1024 | avgt | 10 | 30997.218 | 728.73 | 2473.069 | 5.84 | ns/op | 92.00%
> FloatMaxVector.MULMaskedLanes | 1024 | avgt | 10 | 35515.329 | 227.873 | 3284.17 | 0.608 | ns/op | 90.80%
> IntMaxVector.MULLanes | 1024 | avgt | 10 | 31130.453 | 878.261 | 3304.118 | 5.96 | ns/op | 89.40%
> IntMaxVector.MULMaskedLanes | 1024 | avgt | 10 | 36851.976 | 394.001 | 3969.407 | 0.511 | ns/op | 89.20%
> LongMaxVector.MULLanes | 1024 | avgt | 10 | 58795.752 | 1030.985 | 6883.995 | 3.15 | ns/op | 88.30%
> LongMaxVector.MULMaskedLanes | 1024 | avgt | 10 | 63642.904 | 386.521 | 7892.735 | 9.359 | ns/op | 87.60%
> ShortMaxVector.MULLanes | 1024 | avgt | 10 | 16857.441 | 762.428 | 2287.141 | 0.186 | ns/op | 86.40%
> ShortMaxVector.MULMaskedLanes | 1024 | avgt | 10 | 21171.375 | 74.684 | 2532.913 | 0.274 | ns/op | 88.00%
> 
> </google-sheets-html-origin>

Hamlin Li has updated the pull request incrementally with two additional commits since the last revision:

 - rename
 - remove fp

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/23580/files
  - new: https://git.openjdk.org/jdk/pull/23580/files/b6882221..487ec26e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23580&range=06
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23580&range=05-06

  Stats: 144 lines in 5 files changed: 0 ins; 130 del; 14 mod
  Patch: https://git.openjdk.org/jdk/pull/23580.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23580/head:pull/23580

PR: https://git.openjdk.org/jdk/pull/23580