RFR: 8342095: Add autovectorizer support for subword vector casts [v4]

[Jasmine Karthikeyan]

On Thu, 13 Feb 2025 10:10:34 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> test/hotspot/jtreg/compiler/loopopts/superword/TestCompatibleUseDefTypeSize.java line 333:
>> 
>>> 331:         applyIfPlatform = {"64-bit", "true"},
>>> 332:         applyIf = {"AlignVector", "false"},
>>> 333:         applyIfCPUFeature = {"avx", "true"})
>> 
>> This may be a little nit-picky. But why have a new test-file when this test here was already trying to cover the conversion cases? I think I wrote it back then, and was just too lazy to write all conversion cases. I'd suggest you move your cases up here ;)
>
> I think I added these tests when I was reworking `SuperWord::is_velt_basic_type_compatible_use_def`, which you are now touching as well 😊

I think I didn't realize this test was there when I was working on my patch, but I agree it makes sense to move it there for clarity.

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PR Review Comment: https://git.openjdk.org/jdk/pull/23413#discussion_r1954845649