RFR: 8347405: MergeStores with reverse bytes order value [v5]

[kuaiwei]

On Mon, 20 Jan 2025 07:18:57 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> src/hotspot/share/opto/memnode.cpp line 3276:
>> 
>>> 3274:       merged_input_value = _phase->transform(new ReverseBytesINode(nullptr, merged_input_value));
>>> 3275:     } else {
>>> 3276:       return nullptr;
>> 
>> Suggestion:
>> 
>>       // <say why we cannot do anything for 2-element byte case>.
>>       return nullptr;
>
> Can you please put a comment here about the limitations?

I will support 2-bytes reverse too. I'm not clear if I need ReverseBytesUS or ReverseBytesS here.

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PR Review Comment: https://git.openjdk.org/jdk/pull/23030#discussion_r1923138343