Re: RFR: 8338930: StringConcatFactory hardCoded string concatenation strategy [v3]

[ExE Boss]

On Sun, 25 Aug 2024 14:29:16 GMT, Shaojin Wen <d...@openjdk.org> wrote:

>> This is a follow-up to PR #20273, which improves performance when the number 
>> of parameters exceeds 20.
>> 
>> When the number of parameters is large, the possibility of reuse will be 
>> lower, so we can use the static concat method and write the length and coder 
>> directly into the bytecode to solve the performance regression problem.
>
> Shaojin Wen has updated the pull request incrementally with one additional 
> commit since the last revision:
> 
>   add control flag `reuseThreshold`

As the `paramTypes` passed to `MethodType​::methodType(…)` and 
`MethodTypeDesc​::of(…)` are guaranteed valid and aren’t mutated afterwards, 
this can use `MethodType​::methodType​(…, trusted = true)` and 
`MethodTypeDescImpl​::ofValidated(…)`:

src/java.base/share/classes/java/lang/invoke/StringConcatFactory.java line 1202:

> 1200:                 paramTypes[i + prefixArgs] = needStringOf(cl) ? 
> CD_String : ConstantUtils.classDesc(cl);
> 1201:             }
> 1202:             return MethodTypeDesc.of(CD_int, paramTypes);

Suggestion:

            return MethodTypeDescImpl.ofValidated(CD_int, paramTypes);

src/java.base/share/classes/java/lang/invoke/StringConcatFactory.java line 1219:

> 1217:                 }
> 1218:             }
> 1219:             return MethodTypeDesc.of(CD_int, paramTypes);

Suggestion:

            return MethodTypeDescImpl.ofValidated(CD_int, 
paramTypes.toArray(ConstantUtils.EMPTY_CLASSDESC));

src/java.base/share/classes/java/lang/invoke/StringConcatFactory.java line 1234:

> 1232:                 paramTypes[i + 1] = needStringOf(cl) ? CD_String : 
> ConstantUtils.classDesc(cl);
> 1233:             }
> 1234:             return MethodTypeDesc.of(CD_int, paramTypes);

Suggestion:

            return MethodTypeDescImpl.ofValidated(CD_int, paramTypes);

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

PR Review: https://git.openjdk.org/jdk/pull/20675#pullrequestreview-2259314494
PR Review Comment: https://git.openjdk.org/jdk/pull/20675#discussion_r1730377690
PR Review Comment: https://git.openjdk.org/jdk/pull/20675#discussion_r1730377709
PR Review Comment: https://git.openjdk.org/jdk/pull/20675#discussion_r1730377739