The MemorySegment::mismatch implementation added vectorized mismatch of long sizes. The implementation is trivial, but the starting point for a more optimized implementation, if needed. ArraysSupport::vectorizedMismatchLarge incorrectly returns the bitwise complement of the offset of the first mismatch, where it should return the bitwise complement of the number of remaining pairs of elements to be checked in the tail of the two arrays. The AbstractMemorySegmentImpl::mismatch masked this problem, since it seamlessly compared the remaining tail, which is larger than it should be.
Webrev: https://cr.openjdk.java.net/~chegar/8247696/webrev.00/ I updated the exiting BulkOps micro-benchmark to cover mismatch. Here are the results, compared to ByteBuffer::mismatch, on my machine: Benchmark Mode Cnt Score Error Units BulkOps.mismatch_large_bytebuffer avgt 30 740186.973 ? 119314.207 ns/op BulkOps.mismatch_large_segment avgt 30 683475.305 ? 76355.043 ns/op BulkOps.mismatch_small_bytebuffer avgt 30 7.367 ? 0.523 ns/op BulkOps.mismatch_small_segment avgt 30 4.140 ? 0.602 ns/op -Chris.
