On Fri, 30 Oct 2026 08:31:34 GMT, Jatin Bhateja <[email protected]> wrote:
>> Hi All,
>>
>> x86 AVX-512 targets provides packed shifts for 16, 32, and 64-bit lanes, but
>> not for bytes. C2 lowers LShiftVB, RShiftVB, and URShiftVB by widening bytes
>> to words, shifting, masking, and packing. That sequence is the byte-shift
>> bottleneck.
>>
>> GFNI **gf2p8affineqb** instruction applies one 8×8 bit matrix to every byte.
>> Logical left, logical right, and arithmetic right shifts by 0..7 are fixed
>> matrices derived from the identity 0x0102040810204080.
>>
>> Patch uses this lowering for 128-, 256-, and 512-bit vectors when GFNI is
>> available and keeps the existing widen/shift/pack path when GFNI is absent.
>>
>> Following are the performance numbers of benchmark included with the patch.
>>
>> System: AMD EPYC 9755 128-Core Processor (Turin) Fixed frequency 2.5Ghz
>>
>> Baseline:-
>> ----------
>> Benchmark (shift) Mode Cnt Score Error Units
>> ByteShiftBenchmark.ashr128 3 thrpt 2 24787.795 ops/us
>> ByteShiftBenchmark.ashr256 3 thrpt 2 29184.019 ops/us
>> ByteShiftBenchmark.ashr512 3 thrpt 2 42397.653 ops/us
>> ByteShiftBenchmark.lshl128 3 thrpt 2 25241.434 ops/us
>> ByteShiftBenchmark.lshl256 3 thrpt 2 28274.012 ops/us
>> ByteShiftBenchmark.lshl512 3 thrpt 2 47331.675 ops/us
>> ByteShiftBenchmark.lshr128 3 thrpt 2 25197.166 ops/us
>> ByteShiftBenchmark.lshr256 3 thrpt 2 27587.841 ops/us
>> ByteShiftBenchmark.lshr512 3 thrpt 2 38011.674 ops/us
>>
>> Withopt:-
>> ---------
>> Benchmark (shift) Mode Cnt Score Error Units
>> ByteShiftBenchmark.ashr128 3 thrpt 2 30674.163 ops/us
>> ByteShiftBenchmark.ashr256 3 thrpt 2 43275.297 ops/us
>> ByteShiftBenchmark.ashr512 3 thrpt 2 72744.344 ops/us
>> ByteShiftBenchmark.lshl128 3 thrpt 2 28799.612 ops/us
>> ByteShiftBenchmark.lshl256 3 thrpt 2 40797.362 ops/us
>> ByteShiftBenchmark.lshl512 3 thrpt 2 82156.329 ops/us
>> ByteShiftBenchmark.lshr128 3 thrpt 2 30325.171 ops/us
>> ByteShiftBenchmark.lshr256 3 thrpt 2 42775.756 ops/us
>> ByteShiftBenchmark.lshr512 3 thrpt 2 65255.800 ops/us
>>
>>
>>
>> Kindly review and share your feedback.
>>
>> Best Regards,
>> Jatin
>>
>> ---------
>> - [x] I confirm that I make th...
>
> Jatin Bhateja has updated the pull request incrementally with one additional
> commit since the last revision:
>
> Review comments resolution
test/hotspot/jtreg/compiler/vectorapi/TestGFNIUniformByteShift.java line 48:
> 46: * @library /test/lib /
> 47: * @requires vm.compiler2.enabled
> 48: * @run driver ${test.main.class}
We should also run this test with UseAVX=0, 1, and 2. So may be additional run
directives?
test/hotspot/jtreg/compiler/vectorapi/TestGFNIUniformByteShift.java line 188:
> 186: applyIfCPUFeatureAnd = {"gfni", "true", "avx", "true"})
> 187: public static void testAutoVecArithmeticRightShift() {
> 188: for (int s = 0; s < SHIFT; s++) {
Adding some out of range values for SHIFT would be good to add for auto
vectorization tests.
test/micro/org/openjdk/bench/jdk/incubator/vector/ByteShiftBenchmark.java line
69:
> 67: }
> 68: }
> 69:
An auto vectorizer test in the jmh would be good to add as well.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/33113#discussion_r4447931264
PR Review Comment: https://git.openjdk.org/jdk/pull/33113#discussion_r4447993166
PR Review Comment: https://git.openjdk.org/jdk/pull/33113#discussion_r4447946204
