RFR: 8309811: BytecodePrinter cannot handle unlinked classes [v2]

[Coleen Phillimore]

On Tue, 27 Jun 2023 05:27:31 GMT, Ioi Lam <iklam at openjdk.org> wrote:

>> `BytecodePrinter` assumes that it's printing a method from a linked class (e.g., it assumes that the two bytes following an `invokestatic` bytecode have been rewritten to be a `ConstantPoolCache` index.)
>> 
>> This works fine for `-XX:+TraceBytecodes`, which prints only code from linked classes. However, it doesn't work `Method::print_codes_on()` for a method from an unlinked class.
>> 
>> The old code in `BytecodePrinter` uses a very convoluted logic to go from the rewritten index back to the `cp_index`. It's also difficult to understand the type of the indices from the badly named variables like `i` and `orig_i`.
>> 
>> I had to rewrite all the logic for fetching the indices. Now they are in this form:
>> 
>> 
>>     case Bytecodes::_putfield:
>>     case Bytecodes::_getfield:
>>       {
>>         int cp_index;
>>         if (is_linked()) {
>>           int cpcache_index = get_native_index_u2();
>>           cp_index = cpcache()->entry_at(cpcache_index)->constant_pool_index();
>>         } else {
>>           cp_index = get_Java_index_u2();
>>         }
>>         print_field_or_method(cp_index, st);
>>       }
>> 
>> 
>> The indices have names like `cp_index`, `cpcache_index`, `indy_index` so we know exactly what we are dealing with.
>> 
>> Other changes:
>> - Added test cases to cover both linked/unlinked classes for the bytecodes modified by this PR
>> - Fixed the printing of strings to escape unprintable characters (E.g., "\u0001" is very common used by indified string concat)
>> - Added a test case for `-XX:+TraceBytecodes`
>> - Added a develop flag `-XX:TraceBytecodesStopAt=` so the test cases won't produce excessive output.
>
> Ioi Lam has updated the pull request incrementally with one additional commit since the last revision:
> 
>   @coleenp comments

Ok, looks good.

-------------

Marked as reviewed by coleenp (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/14623#pullrequestreview-1500880871