While instrumenting JDK trunk (at least as of fe3be498b83e70a9f4739ddad6642c3aa04a97d3) I got next messages in the output:

SEVERE : SHOULD NOT OCCUR: unknown cp_type: 17
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 0
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 0
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 25
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 76
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 106
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 97
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 118
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 97
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 47
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 108
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 97
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 110
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 103
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 47
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 69
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 110
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 117
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 109
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 36
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 69
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 110
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 117
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 109
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 68
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 101
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 115
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 99
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 59
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 17
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 0
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 17
SEVERE : SHOULD NOT OCCUR: unknown cp_type: 0
SEVERE : Error reading data from '/Users/shura/JDK/git/jdk/build/macosx-aarch64/support/jcov/temp/jdk-jcov/jmod_temp/jdk.jpackage/classes/jdk/jpackage/internal/PackageBuilder.class' - skipped
Exception details: NPE in com.sun.tdk.jcov.instrument.asm.ClassMorph.computeCheckSum(ClassMorph.java:462)

The instrumented JDK appears to be functional, tests are run, reports are generated.