RFR: JDK-8308994: C2: Re-implement experimental post loop vectorization

[Emanuel Peter]

On Fri, 23 Jun 2023 14:50:32 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> ## TL;DR
>> 
>> This patch completely re-implements C2's experimental post loop vectorization for better stability, maintainability and performance. Compared with the original implementation, this new implementation adds a standalone loop phase in C2's ideal loop phases and can vectorize more post loops. The original implementation and all code related to multi-versioned post loops are deleted in this patch. More details about this patch can be found in the document replied in this pull request.
>
> src/hotspot/share/opto/vmaskloop.cpp line 337:
> 
>> 335:           // For load node, check if it has the same vector element size with
>> 336:           // the bottom type of the statement
>> 337:           if (!same_element_size(mem_type, stmt_bottom_type)) {
> 
> Can this limitation be removed in the future?

Write:
Vector element size does not match of the store in the statement.

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PR Review Comment: https://git.openjdk.org/jdk/pull/14581#discussion_r1239929598