RFR: 8345298: RISC-V: Add riscv backend for Float16 operations - scalar [v7]

[Hamlin Li]

> Hi,
> Can you help to review this patch?
> It's an implementation of https://github.com/openjdk/jdk/pull/22754 on riscv.
> 
> ## Performance
> 
> data
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> Benchmark | (vectorDim) | Mode | Cnt | Score -master | Error | Score - patch | Error | Units | Improvement (master/patch)
> -- | -- | -- | -- | -- | -- | -- | -- | -- | --
> Float16OperationsBenchmark.absBenchmark | 256 | avgt | 10 | 219.564 | 0.076 | 219.597 | 0.081 | ns/op | 1
> Float16OperationsBenchmark.absBenchmark | 512 | avgt | 10 | 358.873 | 0.575 | 355.011 | 0.07 | ns/op | 1.011
> Float16OperationsBenchmark.absBenchmark | 1024 | avgt | 10 | 582.361 | 0.189 | 581.832 | 0.006 | ns/op | 1.001
> Float16OperationsBenchmark.absBenchmark | 2048 | avgt | 10 | 1035.633 | 0.239 | 1034.854 | 0.284 | ns/op | 1.001
> Float16OperationsBenchmark.addBenchmark | 256 | avgt | 10 | 4951.702 | 0.194 | 2593.835 | 0.066 | ns/op | 1.909
> Float16OperationsBenchmark.addBenchmark | 512 | avgt | 10 | 9867.909 | 0.314 | 5167.568 | 0.162 | ns/op | 1.91
> Float16OperationsBenchmark.addBenchmark | 1024 | avgt | 10 | 21324.318 | 1.651 | 10016.456 | 1.07 | ns/op | 2.129
> Float16OperationsBenchmark.addBenchmark | 2048 | avgt | 10 | 42618.969 | 3.877 | 19985.662 | 1.233 | ns/op | 2.132
> Float16OperationsBenchmark.cosineSimilarityDequantizedFP16 | 256 | avgt | 10 | 2811.45 | 0.441 | 2701.419 | 140.699 | ns/op | 1.041
> Float16OperationsBenchmark.cosineSimilarityDequantizedFP16 | 512 | avgt | 10 | 5568.561 | 0.654 | 5577.598 | 1.123 | ns/op | 0.998
> Float16OperationsBenchmark.cosineSimilarityDequantizedFP16 | 1024 | avgt | 10 | 11109.108 | 1.7 | 11095.644 | 0.644 | ns/op | 1.001
> Float16OperationsBenchmark.cosineSimilarityDequantizedFP16 | 2048 | avgt | 10 | 20017.095 | 0.778 | 21560.165 | 0.515 | ns/op | 0.928
> Float16OperationsBenchmark.cosineSimilarityDoubleRoundingFP16 | 256 | avgt | 10 | 20864.303 | 23.768 | 1345.192 | 0.274 | ns/op | 15.51
> Float16OperationsBenchmark.cosineSimilarityDoubleRoundingFP16 | 512 | avgt | 10 | 43596.262 | 102.075 | 2580.035 | 0.397 | ns/op | 16.898
> Float16OperationsBenchmark.cosineSimilarityDoubleRoundingFP16 | 1024 | avgt | 10 | 91565.818 | 250.761 | 5191.12 | 64.598 | ns/op | 17.639
> Fl...

Hamlin Li has updated the pull request incrementally with one additional commit since the last revision:

  refine switch

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/23844/files
  - new: https://git.openjdk.org/jdk/pull/23844/files/e63061d2..3957bbca

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23844&range=06
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23844&range=05-06

  Stats: 75 lines in 1 file changed: 28 ins; 34 del; 13 mod
  Patch: https://git.openjdk.org/jdk/pull/23844.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23844/head:pull/23844

PR: https://git.openjdk.org/jdk/pull/23844