[jdk21u] RFR: 8316679: C2 SuperWord: wrong result, load should not be moved before store if not comparable

[Paul Hohensee]

On Mon, 6 Nov 2023 15:40:00 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Unclean backport to fix the vectorization bug. The patch is unclean because JDK 21u does not have [JDK-8312332](https://bugs.openjdk.org/browse/JDK-8312332) refactoring, that I do not want to backport. I have reapplied the patch by renaming `SWPointer` again.
> 
> Note @eme64, @TobiHartmann.
> 
> Additional testing:
>  - [x] MacOS AArch64 Server fastdebug, new regression test fails without the patch, passes with it
>  - [x] MacOS AArch64 Server fastdebug, `compiler/loopopts`
>  - [x] Linux x86_64 server fastdebug, `tier1 tier2 tier3 tier4`

Marked as reviewed by phh (Reviewer).

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PR Review: https://git.openjdk.org/jdk21u/pull/327#pullrequestreview-1721118124