RFR: 8347405: MergeStores with reverse bytes order value [v10]

[kuaiwei]

> This patch enhance MergeStores optimization to support merge value with reverse byte order.
> 
> Below is benchmark result before and after the patch:
> 
> On aliyun g8y (aarch64)
> |name   | before        | score2        | ratio |
> |---|---|---|---|
> |MergeStoreBench.setCharBS      |5669.655000    |5669.566000    | 0.00 %|
> |MergeStoreBench.setCharBV      |5516.911000    |5516.273000    | 0.01 %|
> |MergeStoreBench.setCharC       |5578.644000    |5552.809000    | 0.47 %|
> |MergeStoreBench.setCharLS      |5782.140000    |5779.264000    | 0.05 %|
> |MergeStoreBench.setCharLV      |5496.403000    |5499.195000    | -0.05 %|
> |MergeStoreBench.setIntB        |6087.703000    |2768.385000    | 119.90 %|
> |MergeStoreBench.setIntBU       |6733.813000    |2950.240000    | 128.25 %|
> |MergeStoreBench.setIntBV       |1362.233000    |1361.821000    | 0.03 %|
> |MergeStoreBench.setIntL        |2834.785000    |2833.042000    | 0.06 %|
> |MergeStoreBench.setIntLU       |2947.145000    |2946.874000    | 0.01 %|
> |MergeStoreBench.setIntLV       |5506.791000    |5506.229000    | 0.01 %|
> |MergeStoreBench.setIntRB       |7634.279000    |5611.058000    | 36.06 %|
> |MergeStoreBench.setIntRBU      |7766.737000    |5551.281000    | 39.91 %|
> |MergeStoreBench.setIntRL       |5689.793000    |5689.385000    | 0.01 %|
> |MergeStoreBench.setIntRLU      |5628.287000    |5628.789000    | -0.01 %|
> |MergeStoreBench.setIntRU       |5536.039000    |5534.910000    | 0.02 %|
> |MergeStoreBench.setIntU        |5595.363000    |5567.810000    | 0.49 %|
> |MergeStoreBench.setLongB       |13722.671000   |6811.098000    | 101.48 %|
> |MergeStoreBench.setLongBU      |13728.844000   |4280.240000    | 220.75 %|
> |MergeStoreBench.setLongBV      |2785.255000    |2785.949000    | -0.02 %|
> |MergeStoreBench.setLongL       |5714.615000    |5710.402000    | 0.07 %|
> |MergeStoreBench.setLongLU      |4128.746000    |4129.324000    | -0.01 %|
> |MergeStoreBench.setLongLV      |2793.125000    |2794.438000    | -0.05 %|
> |MergeStoreBench.setLongRB      |14465.223000   |7015.050000    | 106.20 %|
> |MergeStoreBench.setLongRBU     |14546.954000   |6173.210000    | 135.65 %|
> |MergeStoreBench.setLongRL      |6816.145000    |6813.348000    | 0.04 %|
> |MergeStoreBench.setLongRLU     |4289.445000    |4284.239000    | 0.12 %|
> |MergeStoreBench.setLongRU      |3132.471000    |3133.093000    | -0.02 %|
> |MergeStoreBench.setLongU       |3086.779000    |3087.298000    | -0.02 %|
> 
> AMD EPYC 9T24
> |name   | before | after  | ratio |
> |---|---|---|---|
> |MergeStoreBench.setChar...

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

  Fix test502aBE

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/23030/files
  - new: https://git.openjdk.org/jdk/pull/23030/files/1e1113ed..f773fa36

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23030&range=09
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23030&range=08-09

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/23030.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23030/head:pull/23030

PR: https://git.openjdk.org/jdk/pull/23030