The implementations of equals, compare and mismatch can be reimplemented using underlying mismatch methods that in turn defer to a single method, vectorizedMismatch, that accesses the memory contents of arrays using Unsafe.getLongUnaligned.
The vectorizedMismatch implemetnation can be optimized efficiently by C2 to obtain an approximate 8x speed up when performing a mismatch on byte[] arrays (of a suitable size to overcome fixed costs).
The contract of vectorizedMismatch is simple enough that it can be made an intrinsic (see JDK-8044082) and leverage SIMDs instructions to perform operations up to a width of say 512 bits on supported architectures. Thus even further performance improvements may be possible.
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JDK-8044082 Efficient array comparison intrinsics
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- Draft
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- is blocked by
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JDK-8033148 Lexicographic comparators and mismatchers for arrays
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- Closed
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- relates to
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JDK-8172156 (array) Tune thresholds for vectorized mismatch in Arrays.equals()
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- Open
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- Closed
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- Closed
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- Open
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- Resolved
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