Class.getName() not inlined at concatenation expression

[Сергей Цыпанов]

Hello,

it seems Class.getName() cannot be inlined by optimizing compiler due to inner if-block.

As Andrey Pangin explained [1] the reason is profile polution and C1/C2 cannot eliminate inner branch.
This results in regression which can be demonstrated by this benchmark:

@OutputTimeUnit(TimeUnit.NANOSECONDS)
public class BrokenConcatenationBenchmark {

  @Benchmark
  public String slow(Data data) {
    final Class<? extends Data> clazz = data.clazz;
    return "class " + clazz.getName();
  }

  @Benchmark
  public String fast(Data data) {
    final Class<? extends Data> clazz = data.clazz;
    final String clazzName = clazz.getName();
    return "class " + clazzName;
  }

  @State(Scope.Thread)
  public static class Data {
    final Class<? extends Data> clazz = getClass();

    @Setup
    public void setup() {
      //explicitly load name via native method Class.getName0()
      clazz.getName();
    }
  }
}

I propose to extract Class.getName() expression into a separate variable in some core classes (Class, MethodHandleProxies, Object and URLConnection).
This change is useless in later JDKs yet seems to be valid for JDK8 where we do not have indified String concatenation.
Patch is attached.


1. https://stackoverflow.com/questions/59157085/java-8-class-getname-slows-down-string-concatenation-chain
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