Issue was found by Anton Ivanov:
"DecrementExactLongTest.java and IncrementExactLongTest.java fails on amd64 platform. I suppose a product bug (no intrinsic are used where it should be)"
these tests were integrated in JDK-8028587
the root cause is wrong signaturies in src/share/vm/classfile/vmSymbols.hpp, both methods use long2_long_signature, but it has to be long_long_signature.
do_intrinsic(_decrementExactL, java_lang_Math, decrementExact_name, long2_long_signature, F_S)
do_intrinsic(_incrementExactL, java_lang_Math, incrementExact_name, long2_long_signature, F_S)