RFR: 8357289: Break down the String constructor into smaller methods [v7]

[Chen Liang]

On Mon, 26 May 2025 19:20:06 GMT, Shaojin Wen <swen at openjdk.org> wrote:

>> Through JVM Option +PrintInlining, we found that String has a constructor codeSize of 852, which is too large. This caused failed to inline.
>> 
>> The following is the output information of PrintInlining:
>> 
>>                 @ 9   java.lang.String::<init> (12 bytes)   inline (hot)
>> !m                 @ 1   java.nio.charset.Charset::defaultCharset (52 bytes)   inline (hot)
>> !                  @ 8   java.lang.String::<init> (852 bytes)   failed to inline: hot method too big
>> 
>> 
>> In Java code, the big method that cannot be inlined is the following constructor
>> 
>> 
>> String(Charset charset, byte[] bytes, int offset, int length) {}
>> 
>> The above String constructor is too large; break it down into smaller methods with a codeSize under 325 to allow them to be inlined by the C2.
>
> Shaojin Wen has updated the pull request incrementally with one additional commit since the last revision:
> 
>   from @liach

I think the main advantage here is that with smaller, static methods, it allows us to merge these replacement-decode methods with the no-replacement-decode methods. This is already how the encoding methods are arranged, and can simplify maintenance in the future.

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

PR Comment: https://git.openjdk.org/jdk/pull/25290#issuecomment-3001674339