For this method:

static Integer test(Integer[] a) {
    return a[0];
}

when being called from:

static void run() {
    test(new Integer[1]);
}

Then the class check of a would fail and the method gets recompiled. If I change the method to:

static Integer test(Integer[] a) {
    field = new Integer[1];
    return a[0];
}

Then it is clear what is the issue, the class that is put in the new array is:

narrowklass: precise [precise java/lang/Integer: 0x0000759cf0007ff0 (java/io/Serializable,java/lang/Comparable,java/lang/constant/Constable,java/lang/constant/ConstantDesc):Constant:exact * (java/lang/Cloneable,java/io/Serializable): :Constant:exact:flat:refined_type *

While the one that is used in the speculative type check is:

narrowklass: precise [precise java/lang/Integer: 0x0000759cf0007ff0 (java/io/Serializable,java/lang/Comparable,java/lang/constant/Constable,java/lang/constant/ConstantDesc):Constant:exact * (java/lang/Cloneable,java/io/Serializable): :Constant:exact:flat:atomic:refined_type *

(Notice the last part, one is flat:atomic, another is only flat)

Furthermore, if I don't compile run, then there is no decompilation happening. It seems the compiler use a different klass pointer from the one used by the interpreter.