RFR: 8339214: Remove misleading CodeBuilder.loadConstant(Opcode, ConstantDesc) [v2]

[Chen Liang]

On Sat, 31 Aug 2024 10:16:57 GMT, ExE Boss <duke at openjdk.org> wrote:

>> src/jdk.jfr/share/classes/jdk/jfr/internal/EventInstrumentation.java line 679:
>> 
>>> 677:         getEventConfiguration(blockCodeBuilder);
>>> 678:         // stack: [EW] [EW] [EC]
>>> 679:         blockCodeBuilder.loadConstant(eventTypeId);
>> 
>> Does this means an int (single slot) can be pushed if the event type id happens to be below Integer.MAX_VALUE?
>
> No, because the type of `eventTypeId` is `long`, so the boxed type is `Long`, therefore the only instructions are `LDC2_W`, `LCONST_0`, and `LCONST_1`:
> 
> https://github.com/openjdk/jdk/blob/86c4104d86d91fefae3d9dc11e4f2684d29fcde1/src/java.base/share/classes/java/lang/classfile/CodeBuilder.java#L639-L642

No, because int and long are not interchangeable in the jvm. Only subints can be replaced by ints.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20779#discussion_r1739708292