On 2/20/2013 3:21 PM, John Rose wrote:
On Feb 20, 2013, at 11:59 AM, Coleen Phillimore
<coleen.phillim...@oracle.com <mailto:coleen.phillim...@oracle.com>>
wrote:
On 2/20/2013 2:51 PM, John Rose wrote:
On Feb 20, 2013, at 10:20 AM, Coleen Phillimore
<coleen.phillim...@oracle.com <mailto:coleen.phillim...@oracle.com>>
wrote:
Summary: Add JVM_CONSTANT_PseudoString in place of
JVM_CONSTANT_Object and use this tag to distinguish patched pseudo
strings. The original string is retained if it was present.
This is reasonable; it is a good cleanup. If you can propose a name
better than "PseudoString" I'm all ears.
If the string is really meaningless, maybe it can be deleted and we
don't need this JVM_CONSTANT_PseudoString. The only reason I kept
"String" in the name is because I thought the string would have some
meaning to be preserved.
The string is meaningless. It is just a waste of UTF8 symbol table space.
Consider getting rid of set_has_pseudo_string. That flag was
present (IIRC) only to tell the GC that there might be non-perm oops
in the constant pool. Do we still need that?
I'd be happy to. I noticed it wasn't being used. Neither is
_has_invokedynamic for that matter. _has_preresolution does do
something.
Not any more. That flag was added for the sake of the
internally-generated bytecodes:
changeset: 2522:ddd894528dbc
user: jrose
date: Thu Jun 23 17:14:06 2011 -0700
summary: 7056328: JSR 292 invocation sometimes fails in adapters
for types not on boot class path
It appears that we can get rid of all those flags.
Awesome.
I'm not sure how class file reconstitution for pseudo-strings is
going to work, but I thought it was prudent to leave the Symbol* in
the slot for the patched string.
If you really wanted to reconstitute a class file for an anonymous
class, and if that class has oop patching (pseudo-strings), you
would need either to (a) reconstitute the patches array handed to
Unsafe.defineAnonymousClass, or (b) accept whatever odd strings were
there first, as an approximation. The "odd strings" are totally
insignificant, and are typically something like
"CONSTANT_PLACEHOLDER_42" (see
InvokerBytecodeGenerator::constantPlaceholder).
Maybe there isn't a way or API to reconstitute an anonymous class.
I don't know if there is.
If reconstituting a class means recovering the parameters originally
passed to defineClass, then anonymous classes with patching are
inherently a special case. I wouldn't worry about it too much.
Okay, it would probably be done with patching and never recover the
string constant.
I'm not sure how to reconstitute a normal class in the first place.
Maybe Serguei can comment. If this class cannot be reconsitituted,
I'll change this to remove the string in the patched case and won't
need JVM_CONSTANT_PseudoString (and the constant for Object can be
removed too).
Won't we need a tag that says "this thing is a patched constant"?
JVM_CONSTANT_Patched?
If I null out the Symbol* value in JVM_CONSTANT_String, I won't need a
special constant pool constant. I missed some places to add
JVM_CONSTANT_PseudoString in my edit (as you noticed with
loadable_constant). I hate this extra constant.
I want to revert to the original change (to null out the Symbol* to
indicate it's patched), and add the Object tag and flags cleanup.
Thanks for the info how this works. I'll send out another webrev later.
Coleen
— John
