Accessing runtime directly in LibraryCallKit without going through ci

[John Rose]

On Jul 3, 2014, at 4:04 PM, Krystal Mok <rednaxelafx at gmail.com> wrote:

> Hi everyone,
> 
> I just came across this piece of code in C2 LibraryCallKit:
> 
> http://hg.openjdk.java.net/jdk9/jdk9/hotspot/file/39bac689e998/src/share/vm/opto/library_call.cpp#l435
> 
> 433:  case vmIntrinsics::_getCallerClass:
> 434:     if (!InlineReflectionGetCallerClass)  return NULL;
> 435:     if (SystemDictionary::reflect_CallerSensitive_klass() == NULL)  return NULL;
> 436:     break;
> 
> Line 435 is accessing the runtime (SystemDictionary) directly without going through ci.
> Apparently it runs "okay" in current HotSpot. But as a convention, should it be changed to go through ci? i.e.
> 
> if (C->env()->reflect_CallerSensitive_klass() == NULL)  return NULL;

Yes, it should go through the CI.  It happens to run OK since it is just a null check of a Klass* value, and the GC does not convert null to non-null values.  (This would be a slight hazard if the value were a compressed klass pointer.)

— John
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