JDK-7086585 : make Java field injection more flexible
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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.
See main CR
7086585: make Java field injection more flexible
Reviewed-by: jrose, twisti, kvn, coleenp
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
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 http://cr.openjdk.java.net/~never/7088481.