RFR: 8295893: Improve printing of Constant Pool Cache Entries
Matias Saavedra Silva
matsaave at openjdk.org
Tue Oct 25 22:27:20 UTC 2022
On Tue, 25 Oct 2022 19:37:12 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$MH+0x0000000801000400' (0x23e03be8)
> - private 'asTypeCache' 'Ljava/lang/invoke/MethodHandle;' @24 NULL (0x00000000)
> - private 'asTypeSoftCache' 'Ljava/lang/ref/SoftReference;' @28 NULL (0x00000000)
> - final 'argL0' 'Ljava/lang/Object;' @32 a 'java/lang/invoke/DirectMethodHandle'{0x000000011f019b70} (0x23e0336e)
> - final 'argL1' 'Ljava/lang/Object;' @36 "000"{0x000000011f0193d0} (0x23e0327a)
> -------------
> 15 putstatic 17 <Concat0.d/Ljava/lang/String;>
> 18 iinc #1 1
> 21 goto 2
> 24 return
Calling findmethod will result in this output for an invokedynamic call:
(gdb) call findmethod("Concat0", "main", 0x8)
"Executing findmethod"
flags (bitmask):
0x01 - print names of methods
0x02 - print bytecodes
0x04 - print the address of bytecodes
0x08 - print info for invokedynamic
0x10 - print info for invokehandle
[ 0] 0x0000000801000800 class Concat0 loader data: 0x00007ffff02ddeb0 for instance a 'jdk/internal/loader/ClassLoaders$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
You can see that the flag value is currently decoded twice, once as a quick translation and once in full detail. Printing will look nearly identical for a field but with different flags and no appendix.
-------------
PR: https://git.openjdk.org/jdk/pull/10860
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