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

[Nicole Xu]

On Wed, 8 Jan 2025 09:04:47 GMT, Nicole Xu <duke 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()` resulting in the IndexOutOfBoundsException error. On the other hand, the unified index for 128-bit, 256-bit and 512-bit species might not be proper since it leaves gaps in between when accessing the data for 128-bit and 256-bit species. This will unnecessarily include the noise due to cache misses or (on some targets) prefetching additional cache lines which are not usable, thereby impacting the crispness of microbenchmark.
> 
> Hence, we improved the benchmark from several aspects,
> 1. Used sufficient number of predicated operations within the vector loop while minimizing the noise due to memory operations.
> 2. Modified the index computation logic which can now withstand any ARRAYLEN without resulting in an IOOBE.
> 3. Removed redundant vector read/writes to instance fields, thus eliminating significant boxing penalty which translates into throughput gains.

This pull request has now been integrated.

Changeset: 107ee878
Author:    Nicole Xu <yuyangx at nvidia.com>
URL:       https://git.openjdk.org/jdk/commit/107ee878d66f4006f102c1fd12af3bf156a25757
Stats:     145 lines in 1 file changed: 5 ins; 29 del; 111 mod

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

Co-authored-by: Jatin Bhateja <jbhateja at openjdk.org>
Reviewed-by: jbhateja, xgong

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PR: https://git.openjdk.org/jdk/pull/22963