RFR: 8346954: [JMH] jdk.incubator.vector.MaskedLogicOpts fails due to IndexOutOfBoundsException

[Jatin Bhateja]

On Thu, 13 Feb 2025 12:06:09 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> Suite MaskedLogicOpts.maskedLogicOperationsLong512() failed on both x86 and AArch64 with the following error:
>> 
>> 
>> java.lang.IndexOutOfBoundsException: Index 252 out of bounds for length 249
>> 
>> 
>> The variable `long256_arr_idx` is misused when indexing  'LongVector l2, l3, l4, l5' in function `maskedLogicOperationsLongKernel()`. 'long256_arr_idx' increases by 4 every time the benchmark runs and ensures the incremented value remains within the bounds of the array. However, for `LongVector.SPECIES_512`, it loads 8 numbers from the array each time the benchmark runs, resulting in an out-of-range indexing issue.
>> 
>> Hence, we revised the index variables from `long256_arr_idx` to `long512_arr_idx`, which has a stride of 8, to ensure that the loaded vector is inside of the array boundary for all vector species. This is also consistent with other kernel functions.
>> 
>> Additionally, some defined but unused variables have been removed.
>
> test/micro/org/openjdk/bench/jdk/incubator/vector/MaskedLogicOpts.java line 122:
> 
>> 120:     @Setup(Level.Invocation)
>> 121:     public void init_per_invoc() {
>> 122:         int512_arr_idx = (int512_arr_idx + 16) & (ARRAYLEN-1);
> 
> Benchmark assumes that ARRAYLEN is a POT value, thus it will also be good to use the modulous operator for rounding here, it will be expensive but will not impact the performance of the Benchmarking kernels.

Please try with following command line
`java -jar target/benchmarks.jar -f 1 -i 2 -wi 1 -w 30 -p ARRAYLEN=30 MaskedLogic`

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PR Review Comment: https://git.openjdk.org/jdk/pull/22963#discussion_r1954384129