RFR: 8295893: Improve printing of Constant Pool Cache Entries [v2]

[David Holmes]

On Wed, 26 Oct 2022 19:22:34 GMT, Matias Saavedra Silva <matsaave at openjdk.org> wrote:

>> As an extension of [JDK-8292699](https://bugs.openjdk.org/browse/JDK-8292699), this aims to further improve the printing of Constant Pool Cache entries. The contents and flag are decoded into human readable text with an appendix printed as before.
>> 
>> The text format and contents are tentative, please review.
>> 
>> Here is an example output when using `findmethod()`:
>> 
>> "Executing findmethod"
>> flags (bitmask):
>>    0x01  - print names of methods
>>    0x02  - print bytecodes
>>    0x04  - print the address of bytecodes
>>    0x08  - print info for invokedynamic
>>    0x10  - print info for invokehandle
>> 
>> [  0] 0x0000000801000800 class Concat0 loader data: 0x00007ffff02ddeb0 for instance a 'jdk/internal/loader/ClassLoaders$AppClassLoader'{0x00000007fef59110}
>> 0x00007fffa0400368 static method main : ([Ljava/lang/String;)V
>>    0 iconst_0
>>    1 istore_1
>>    2 iload_1
>>    3 iconst_2
>>    4 if_icmpge 24
>>    7 getstatic 7 <Concat0.s/Ljava/lang/String;> 
>>   10 invokedynamic bsm=31 13 <makeConcatWithConstants(Ljava/lang/String;)Ljava/lang/String;>
>>   BSM: REF_invokeStatic 32 <java/lang/invoke/StringConcatFactory.makeConcatWithConstants(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/String;[Ljava/lang/Object;)Ljava/lang/invoke/CallSite;> 
>>   arguments[1] = {
>>      000
>>   }
>>   ConstantPoolCacheEntry:   4
>>  - this: 0x00007fffa0400570
>>  - bytecode 1: invokedynamic ba
>>  - bytecode 2: nop 00
>>  - cp index:    13
>>  - F1:  [   0x00000008000c8658]
>>  - F2:  [   0x0000000000000003]
>>  -     Method: 0x00000008000c8658 java.lang.Object java.lang.invoke.Invokers$Holder.linkToTargetMethod(java.lang.Object, java.lang.Object)
>>  - flag values: [08|0|0|1|1|0|1|0|0|0|00|00|02]
>>  - tos: object
>>  - local signature: 1
>>  - has appendix: 1
>>  - forced virtual: 0
>>  - final: 1
>>  - virtual Final: 0
>>  - resolution Failed: 0
>>  - num Parameters: 02
>>   Method: 0x00000008000c8658 java/lang/invoke/Invokers$Holder.linkToTargetMethod(Ljava/lang/Object;Ljava/lang/Object;)Ljava/lang/Object;
>>   appendix: java.lang.invoke.BoundMethodHandle$Species_LL 
>> {0x000000011f021360} - klass: 'java/lang/invoke/BoundMethodHandle$Species_LL'
>>  - ---- fields (total size 5 words):
>>  - private 'customizationCount' 'B' @12  0 (0x00)
>>  - private volatile 'updateInProgress' 'Z' @13  false (0x00)
>>  - private final 'type' 'Ljava/lang/invoke/MethodType;' @16  a 'java/lang/invoke/MethodType'{0x000000011f0185b0} = (Ljava/lang/String;)Ljava/lang/String; (0x23e030b6)
>>  - final 'form' 'Ljava/lang/invoke/LambdaForm;' @20  a 'java/lang/invoke/LambdaForm'{0x000000011f01df40} => a 'java/lang/invoke/MemberName'{0x000000011f0211e8} = {method} {0x00007fffa04012a8} 'invoke' '(Ljava/lang/Object;Ljava/lang/Object;)Ljava/lang/Object;' in 'java/lang/invoke/LambdaForm$MH+0x0000000801000400' (0x23e03be8)
>>  - private 'asTypeCache' 'Ljava/lang/invoke/MethodHandle;' @24  NULL (0x00000000)
>>  - private 'asTypeSoftCache' 'Ljava/lang/ref/SoftReference;' @28  NULL (0x00000000)
>>  - final 'argL0' 'Ljava/lang/Object;' @32  a 'java/lang/invoke/DirectMethodHandle'{0x000000011f019b70} (0x23e0336e)
>>  - final 'argL1' 'Ljava/lang/Object;' @36  "000"{0x000000011f0193d0} (0x23e0327a)
>>                  -------------
>>   15 putstatic 17 <Concat0.d/Ljava/lang/String;> 
>>   18 iinc #1 1
>>   21 goto 2
>>   24 return
>
> Matias Saavedra Silva has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Added null check and resource mark

Updates look good. One further nit, but otherwise seems okay. But someone who is actively going to be using this needs to comment on the format/content changes. Thanks.

src/hotspot/share/oops/cpCache.cpp line 653:

> 651:        bytecode_1() == Bytecodes::_invokedynamic)) {
> 652:       oop appendix = appendix_if_resolved(cph);
> 653:       if (m != NULL) {

Please use nullptr to be consistent with earlier null check.

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

PR: https://git.openjdk.org/jdk/pull/10860