review for 7086585: make Java field injection more flexible

Tom Rodriguez tom.rodriguez at
Fri Sep 9 09:28:09 PDT 2011

On Sep 9, 2011, at 2:05 AM, Christian Thalinger wrote:

> On Sep 8, 2011, at 10:38 PM, Tom Rodriguez wrote:
>> 1577 lines changed: 621 ins; 612 del; 344 mod; 65541 unchg
> agent/src/share/classes/sun/jvm/hotspot/ui/classbrowser/
> 1120                 // TypeArray klfields = kls.getFields();
> You want to keep this line?

Nope.  I deleted it.

> Otherwise this looks good.



>> 7086585: make Java field injection more flexible
>> Reviewed-by:
>> Classes which are special to the JVM often need fields for the VM's
>> use.  Currently the mechanism for this is adhoc or relies on the Java
>> code declaring the needed fields.  We need a mechanism for flexibly
>> injecting needed fields.  The basic idea is to built a standard
>> mechanism for declaring injected fields and to inject them during
>> class file parsing so that they get laid out and tracked like normal
>> fields.  This is also means that they can simply be looked up when CDS
>> is used so we don't have to rely on hardcoding them.  To do this I
>> hide the encoding of the fields array and replaced all existing
>> iteration with a new set of *FieldStream classes.  JavaFieldStream
>> only iterates true Java fields so the behavious of existing code is
>> completely unchanged.
>> The new fields use a special access flag JVM_ACC_INTERNAL to describe
>> themselves and instead of having the name_index and signature_index
>> refer to the constant pool they are vmSymbols::SID so they are looked
>> up directly from the vmSymbols.  All of this is hidden inside the
>> RawFieldDescriptor class which is responsible for decoding fields from
>> the field array.
>> I also cleaned up the field layout code a bit.  I eliminated the
>> _ALIGNED_ AllocationType since there's no longer any difference in how
>> we align double word types.  I turned FieldAllocationCount into a real
>> class and moved some of the layout code into it.
>> I deleted the nonexistent MethodHandle::vmslot field.  I moved
>> ClassLoader::parallelCapable into java_lang_ClassLoader.  I deleted
>> some dead field injection like the Reference.discovered field which
>> has existed since 1.5, and the existing logic for java.lang.Class
>> fields since it now uses the field injection machinery.
>> Tested with runthese, the sajdi tests, the tmtools suite, the nsk
>> regression, jdb, jdi, jvmti, hprof and jit subsuites along with
>> vm/mlvm, but with and without the JDK changes that remove these fields
>> and rely on injection to introduce them.  They will be removed under
>> 7088481 and those changes are
> That looks good too.
> -- Christian

More information about the hotspot-compiler-dev mailing list