RFR: 8365290: [perf] x86 ArrayFill intrinsic generates SPLIT_STORE for unaligned arrays [v5]

[Emanuel Peter]

On Wed, 10 Sep 2025 16:22:32 GMT, Vladimir Ivanov <vaivanov at openjdk.org> wrote:

>> Vladimir Ivanov has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   JDK-8365290 [perf] x86 ArrayFill intrinsic generates SPLIT_STORE for unaligned arrays
>
> The align cycle was updated to counted loop with alignment for 32 bytes (The main loop operates by 32 bytes values and 32bytes alignment enough to have no split_stores). Reported scores on the Xeon 6740E for the compiled version vs intrinsic are:
> 
> SRF | size | jdk26, comp | patched | p/jdk_comp
> -- | -- | -- | -- | --
> ArraysFill.testByteFill | 16 | 152077.563 | 168535.8 | 1.11
> ArraysFill.testByteFill | 31 | 125702.057 | 212504.2 | 1.69
> ArraysFill.testByteFill | 250 | 57965.263 | 127806.6 | 2.20
> ArraysFill.testByteFill | 266 | 44901.157 | 145742 | 3.25
> ArraysFill.testByteFill | 511 | 61918.237 | 109917.3 | 1.78
> ArraysFill.testByteFill | 2047 | 32222.184 | 40348.55 | 1.25
> ArraysFill.testByteFill | 2048 | 31930.607 | 35773.5 | 1.12
> ArraysFill.testByteFill | 8195 | 10690.434 | 10709.71 | 1.00
> ArraysFill.testIntFill | 16 | 144979.804 | 289781.8 | 2.00
> ArraysFill.testIntFill | 31 | 133495.302 | 212475.7 | 1.59
> ArraysFill.testIntFill | 250 | 74178.893 | 80775.39 | 1.09
> ArraysFill.testIntFill | 266 | 68009.933 | 78090.68 | 1.15
> ArraysFill.testIntFill | 511 | 39688.805 | 45553.15 | 1.15
> ArraysFill.testIntFill | 2047 | 11504.203 | 11282.22 | 0.98
> ArraysFill.testIntFill | 2048 | 11245.331 | 11512.12 | 1.02
> ArraysFill.testIntFill | 8195 | 2692.649 | 2654.157 | 0.99
> ArraysFill.testLongFill | 16 | 212541.769 | 212508.9 | 1.00
> ArraysFill.testLongFill | 31 | 137729.599 | 137624.3 | 1.00
> ArraysFill.testLongFill | 250 | 43162.979 | 43155.4 | 1.00
> ArraysFill.testLongFill | 266 | 42173.88 | 42156.26 | 1.00
> ArraysFill.testLongFill | 511 | 23364.859 | 23367.6 | 1.00
> ArraysFill.testLongFill | 2047 | 6122.745 | 6123.296 | 1.00
> ArraysFill.testLongFill | 2048 | 5792.552 | 5772.727 | 1.00
> ArraysFill.testLongFill | 8195 | 616.62 | 616.257 | 1.00
> ArraysFill.testShortFill | 16 | 152176.336 | 354182.7 | 2.33
> ArraysFill.testShortFill | 31 | 137527.651 | 227688.8 | 1.66
> ArraysFill.testShortFill | 250 | 58930.645 | 99614.52 | 1.69
> ArraysFill.testShortFill | 266 | 91088.72 | 93755.19 | 1.03
> ArraysFill.testShortFill | 511 | 65332.79 | 70824.73 | 1.08
> ArraysFill.testShortFill | 2047 | 21713.296 | 22289.87 | 1.03
> ArraysFill.testShortFill | 2048 | 21667.468 | 21021.92 | 0.97
> ArraysFill.testShortFill | 8195 | 5922.318 | 5886.738 | 0.99

@IvaVladimir I'm going on vacation for 3 weeks, so won't be able to review. Feel free to ping others to review.

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PR Comment: https://git.openjdk.org/jdk/pull/26747#issuecomment-3307189076