RFR: 8366333: AArch64: Enhance SVE subword type implementation of vector compress [v4]

[erifan]

On Tue, 30 Sep 2025 06:57:34 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> erifan has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Improve coding style a bit
>
> test/hotspot/jtreg/compiler/vectorapi/VectorCompressTest.java line 170:
> 
>> 168:     @Test
>> 169:     @IR(counts = { IRNode.COMPRESS_VB, "= 1" },
>> 170:         applyIfCPUFeature = { "sve", "true" })
> 
> Hi @erifan,
> Nice work!,
> Can you please also enable these tests for x86? Following are the relevant features. 
> 
> CompressVB     -> avx512_vbmi2, avx512_vl
> CompressVS     -> avx512_vbmi2. avx512_vl
> CompressVI/VF -> avx512f, avx512vl
> ComprssVL/VD -> avx512f, avx512vl
> 
> PS: avx512_vbmi2 is missing from test/IREncodingPrinter.java
> 
> FYI , currently, we don't support sub-word compression intrinsics on AVX2/E-core targets.  I created a vectorized algorithm without any x86 backend change just using vector APIs, and it showed 12x improvement.
> 
> https://github.com/jatin-bhateja/external_staging/blob/main/VectorizedAlgos/SubwordCompress/short_vector_compress.java
> 
> 
> PROMPT>java -cp .  --add-modules=jdk.incubator.vector short_vector_compress 0
> WARNING: Using incubator modules: jdk.incubator.vector
> [ baseline time] 976 ms  [res] 429507073
> PROMPT>java -cp .  --add-modules=jdk.incubator.vector short_vector_compress 1
> WARNING: Using incubator modules: jdk.incubator.vector
> [ withopt time] 80 ms  [res] 429507073
> PROMPT>

Done, please help me check if it is correct, thank you! I have tested it locally.

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PR Review Comment: https://git.openjdk.org/jdk/pull/27188#discussion_r2409522760