RFR: 8347405: MergeStores with reverse bytes order value [v13]

[kuaiwei]

On Wed, 5 Mar 2025 06:40:01 GMT, Fei Yang <fyang at openjdk.org> wrote:

>> kuaiwei has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 19 commits:
>> 
>>  - Merge remote-tracking branch 'origin/master' into pr/merge_stores_reverse
>>  - Add readable comment
>>  - Fix for review comments
>>  - Allow ValueOrder::Reverse on big-endian platforms
>>  - Revert "Merge more stores"
>>    
>>    This reverts commit 1e1113ed02ec5a9fe181f215d5667e8de487fe47.
>>  - Revert "Fix test502aBE"
>>    
>>    This reverts commit f773fa368577c4f67957c4d40968c5c45e3ae205.
>>  - Fix test502aBE
>>  - Merge more stores
>>  - Remove an useless assertion
>>  - Remove tailing white space
>>  - ... and 9 more: https://git.openjdk.org/jdk/compare/aac9cb45...b3243a56
>
> test/hotspot/jtreg/compiler/c2/TestMergeStores.java line 810:
> 
>> 808:                    IRNode.REVERSE_BYTES_L, "1"},
>> 809:         applyIf = {"UseUnalignedAccesses", "true"},
>> 810:         applyIfPlatformAnd = {"little-endian", "true", "riscv64", "false"})   // Exclude RISCV64 because ReverseBytes are not supported
> 
> Seems to me the code comment could be made more accurate. In fact, all the `ReverseBytes` variants will be available on riscv64 if we have the Zbb extension [1]. And I see the newly added IR tests in this file also works on such platforms. I wonder if there is an easy way to enable these IR tests for these platforms.
> 
> [1] https://github.com/openjdk/jdk/blob/master/src/hotspot/cpu/riscv/riscv_b.ad#L181

@RealFYang , thanks for your comments. As you mentioned, IR test framework can not check Zbb extension for RISCV platform, so I disable it for RISCV64. I think we can make a new PR to enhance IR test framework and enable the test.

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PR Review Comment: https://git.openjdk.org/jdk/pull/23030#discussion_r1982457147