(RFR) 8240245: Avoid calling is_shared_class_visible() in SystemDictionary::load_shared_class()

[Yumin Qi]

Hi,

   Please check the updated webrev at: 
http://cr.openjdk.java.net/~minqi/2020/8240245/webrev-01/
   In this version, test case 
test/hotspot/jtreg/runtime/cds/appcds/jigsaw/modulepath/ModulePathAndCP.java
   modfied/added cases to reflect --module-path used at runtime.

   Thanks
   Yumin*
*
On 5/22/20 8:45 AM, Yumin Qi wrote:
> Hi, Please review
>
>   bug: 8240245: https://bugs.openjdk.java.net/browse/JDK-8240245
>   Webrev: http://cr.openjdk.java.net/~minqi/2020/8240245/webrev-00/
>
> Summary: When -Xbootclasspath/a: and --module-path are not specified, 
> for bultin loaders, is_shared_class_visible will always return true so 
> we can skip such check. Another optimization is guarding the call to 
> load_shared_class with UseSharedSpaces, save unnecessary calls for 
> non-shared run.
>
> For java -version, the performance data:
>
> Results of " perf stat -r 40 bin/java -Xshare:on 
> -XX:SharedArchiveFile=jdk2.jsa -Xint -version "
>    1:     59008853    59008564 (  -289)                41.100 40.342 ( 
> -0.758)      --
>    2:     58983285    59026645 ( 43360)  ++++          39.841 40.708 
> (  0.867)    ++
>    3:     59008801    59005425 ( -3376)                39.903 40.881 
> (  0.978)   +++
>    4:     59032045    58990500 (-41545)      ----      39.809 40.443 
> (  0.634)    ++
>    5:     59029813    58976124 (-53689)      -----     40.121 39.238 ( 
> -0.883)      --
>    6:     59036617    58998279 (-38338)      ----      40.644 39.875 ( 
> -0.769)      --
>    7:     59003768    59005109 (  1341)                39.416 38.991 ( 
> -0.425)      -
>    8:     58972545    58985824 ( 13279)     +          40.811 40.001 ( 
> -0.810)      --
>    9:     59007110    58981883 (-25227)      --        40.969 39.090 ( 
> -1.879)      -----
>   10:     58992934    58987333 ( -5601)      -         40.521 40.371 ( 
> -0.150)
> ============================================================
>           59007573    58996566 (-11006)      -         40.310 39.989 ( 
> -0.321)      -
> instr delta =       -11006    -0.0187%
> time  delta =       -0.321 ms -0.7966%
>
> Tests:  tier1,tier2
>
> Thanks
> Yumin