Attached test case taken from recently release parquet-mr bit packing optimization (https://github.com/apache/parquet-mr/commit/d730fa7466f9fa15e1e4a4254f22af9c6783acdc)
shows performance degradation with JDK-21 but work fine with JDK-17,18,19 and 20.

CommandLine:
java --add-modules=jdk.incubator.vector -XX:+UnlockDiagnosticVMOptions -XX:-UseOnStackReplacement -XX:+TraceTypeProfile -XX:TypeProfileLevel=222 -XX:CompileCommand=PrintIntrinsics,VectorBitUnpacker3::unpack8Values_vec -cp . VectorBitUnpacker3


JDK-21
=======
openjdk 21-ea 2023-09-19
OpenJDK Runtime Environment (build 21-ea+25-2212)
OpenJDK 64-Bit Server VM (build 21-ea+25-2212, mixed mode, sharing)
 
TypeProfile shows profile pollution and abstract Species as receiver type.

 jdk.incubator.vector.AbstractShuffle::toBitsVectorTemplate
                                                          @ 9 jdk.incubator.vector.ShortVector$ShortSpecies::elementType (4 bytes)
                                                           \-> TypeProfile (2799/10469 counts) = jdk/incubator/vector/ShortVector$ShortSpecies
 jdk.incubator.vector.AbstractShuffle::toBitsVectorTemplate
                                                          @ 9 jdk.incubator.vector.ByteVector$ByteSpecies::elementType (4 bytes)
                                                           \-> TypeProfile (7670/10469 counts) = jdk/incubator/vector/ByteVector$ByteSpecies
 jdk.incubator.vector.AbstractShuffle::toBitsVectorTemplate
                                                          @ 14 jdk.incubator.vector.ShortVector$ShortSpecies::dummyVector (5 bytes)
                                                           \-> TypeProfile (2799/10469 counts) = jdk/incubator/vector/ShortVector$ShortSpecies
 jdk.incubator.vector.AbstractShuffle::toBitsVectorTemplate
                                                          @ 14 jdk.incubator.vector.ByteVector$ByteSpecies::dummyVector (5 bytes)
                                                           \-> TypeProfile (7670/10469 counts) = jdk/incubator/vector/ByteVector$ByteSpecies



Print-Intrinsics Log:-
                                                        @ 45 jdk.internal.vm.vector.VectorSupport::convert (36 bytes) failed to inline (intrinsic)
                                                                  @ 19 jdk.internal.vm.vector.VectorSupport::fromBitsCoerced (35 bytes) failed to inline (intrinsic)


JDK-20
=======
openjdk 20.0.1 2023-04-18
OpenJDK Runtime Environment (build 20.0.1+9-29)
OpenJDK 64-Bit Server VM (build 20.0.1+9-29, mixed mode, sharing)

No such method name toBitsVectorTemplate in JDK-20.

Intrinsification log shows both the APIs are getting intrinsified
                                        @ 322 jdk.internal.vm.vector.VectorSupport::convert (36 bytes) (intrinsic)
                                        @ 1 java.lang.Object::getClass (0 bytes) (intrinsic)
                                        @ 5 java.lang.Object::getClass (0 bytes) (intrinsic)
                                                  @ 19 jdk.internal.vm.vector.VectorSupport::fromBitsCoerced (35 bytes) (intrinsic)
                                                  @ 1 java.lang.Object::getClass (0 bytes) (intrinsic)
                                                  @ 5 java.lang.Object::getClass (0 bytes) (intrinsic)