On Fri, 10 Jul 2026 03:31:09 GMT, Kuai Wei <[email protected]> wrote: >> I recently noticed a behavioral discrepancy in >> jdk.internal.util.ArraysSupport.vectorizedMismatch between the Java >> implementation and the platform intrinsic implementations. >> >> Current behavior >> >> The Java implementation may leave a tail of elements unchecked, returning >> the bitwise complement of the number of remaining elements (i.e., >> ~remaining). >> The x86_64 intrinsic, by contrast, compares all elements and simply returns >> -1 when no mismatch is found. >> >> Proposed change >> >> This PR refines the Java implementation so that it always compares all >> elements and returns -1 when no mismatch is found, matching the x86_64 >> intrinsic behavior. >> >> A regression test is included at >> `test/hotspot/jtreg/compiler/intrinsics/VectorizedMismatchReturnDiffTest.java` >> which demonstrates the original behavioral difference. >> >> ## Test >> - [x] tier1 test suites on linux x86_64 >> - [x] tier1 test suites on linux aarch64 >> >> --------- >> - [x] I confirm that I make this contribution in accordance with the >> [OpenJDK Interim AI Policy](https://openjdk.org/legal/ai). > > Kuai Wei has updated the pull request incrementally with one additional > commit since the last revision: > > change callsites of other java source
src/java.base/share/classes/jdk/internal/util/ArraysSupport.java line 154: > 152: // boundary and reach an inaccessible page. Copy exact tail > bytes to a temp > 153: // buffer to avoid out-of-bounds access. > 154: byte[] buff = new byte[Long.BYTES]; What's the point of messing with a temp buffer? Why can't you simply compare tail bytes one by one? ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/31802#discussion_r3561389465
