RFR: 8331724: Refactor j.l.constant implementation to internal package [v13]

[Claes Redestad]

On Wed, 15 May 2024 11:17:42 GMT, Claes Redestad <redestad at openjdk.org> wrote:

>> This PR suggests refactoring the implementation classes of java.lang.constant into a new package jdk.internal.constant to enable sharing some trusted static factory methods with users elsewhere in java.base, such as java.lang.invoke and java.lang.classfile. The refactoring also adds some "trusted" methods for use when input is pre-validated, and makes use of them where applicable in the current implementation. There are more changes in the pipeline which will be folded into #17108 or PR'ed once that is integrated. 
>> 
>> There are two optimizations mixed up here. One in `MethodTypeDesc.ofDescriptor`:
>> 
>> Name                                                             (descString) Cnt     Base     Error      Test   Error  Unit  Change
>> MethodTypeDescFactories.ofDescriptor  (Ljava/lang/Object;Ljava/lang/String;)I   6  138,371 ±   0,767   136,939 ± 1,126 ns/op   1,01x (p = 0,000*)
>> MethodTypeDescFactories.ofDescriptor                                      ()V   6   10,528 ±   2,495     4,110 ± 0,047 ns/op   2,56x (p = 0,000*)
>> MethodTypeDescFactories.ofDescriptor ([IJLjava/lang/String;Z)Ljava/util/List;   6  209,390 ±   4,583   196,175 ± 3,211 ns/op   1,07x (p = 0,000*)
>> MethodTypeDescFactories.ofDescriptor                    ()[Ljava/lang/String;   6   36,039 ±   8,684    20,794 ± 1,110 ns/op   1,73x (p = 0,000*)
>> MethodTypeDescFactories.ofDescriptor                                 (..IIJ)V   6  279,139 ±   6,248   187,934 ± 0,857 ns/op   1,49x (p = 0,000*)
>> MethodTypeDescFactories.ofDescriptor                 (.....................).   6 2174,387 ± 132,879  1150,652 ± 3,158 ns/op   1,89x (p = 0,000*)
>>   * = significant
>> 
>> 
>> The other in `ClassDesc::nested`, where to get rid of a simple static method in `ConstantUtils` I ended up speeding up and simplifying the public factory method:
>> 
>> Name                                      Cnt    Base     Error    Test   Error  Unit  Change
>> ClassDescFactories.ReferenceOnly.ofNested   6 209,853 ± 132,525  22,017 ± 0,573 ns/op   9,53x (p = 0,000*)
>>   * = significant
>> 
>> 
>> The optimizations could be split out and PRd independently, but I think they are simple enough to include in this refactoring.
>
> Claes Redestad has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Update src/java.base/share/classes/java/lang/constant/ClassDesc.java
>    
>    Co-authored-by: ExE Boss <3889017+ExE-Boss at users.noreply.github.com>
>  - Update src/java.base/share/classes/java/lang/constant/ClassDesc.java
>    
>    Co-authored-by: ExE Boss <3889017+ExE-Boss at users.noreply.github.com>

FTR I had to back out a change that would delegate to the now simplified and optimized `arrayType()` from `arrayType(int rank)` when `rank` equals `1` since the methods actually throw different exceptions, `IllegalStateException` vs `IllegalArgumentException`. This was caught by a later test. 

Unfortunate that `java.lang.constant` has chosen to use these two in particular since it's easy to miss due to the similarity of the exception names. There are also some unspecified exceptional behavior. For example on `arrayType()` only `IllegalStateException` is specified to be thrown, but calling `ClassDesc.ofDescriptor("V").arrayType()` throws an `IllegalArgumentException`. This behavior is not changed by this PR.

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PR Comment: https://git.openjdk.org/jdk/pull/19105#issuecomment-2112663111