RFR (M) Close alignment gaps in InstanceKlass

[Chris Plummer]

Hi Coleen,

The SA changes look good. BTW, I've already made the 
TestIntConstant.java change in the Loom project. 
InstanceKlass::_misc_is_unsafe_anonymous was already changed to "8" in 
loom. You might want to sync up with Ron to make sure you aren't making 
conflicting changes in this area. Your code looks like:

  249   enum {
  250     _misc_rewritten                           = 1 << 0,  // 
methods rewritten.
  251     _misc_has_nonstatic_fields                = 1 << 1,  // for 
sizing with UseCompressedOops
  252     _misc_should_verify_class                 = 1 << 2,  // allow 
caching of preverification
  253     _misc_is_unsafe_anonymous                 = 1 << 3,  // has 
embedded _unsafe_anonymous_host field
  254     _misc_is_contended                        = 1 << 4,  // marked 
with contended annotation

Loom looks like:

   static const unsigned _misc_kind_field_size = 0;
...
   // Start after _misc_kind field.
   enum {
     _misc_rewritten                           = 1 << 
(_misc_kind_field_size + 0),  // methods rewritten.
     _misc_has_nonstatic_fields                = 1 << 
(_misc_kind_field_size + 1),  // for sizing with UseCompressedOops
     _misc_should_verify_class                 = 1 << 
(_misc_kind_field_size + 2),  // allow caching of preverification
     _misc_is_unsafe_anonymous                 = 1 << 
(_misc_kind_field_size + 3),  // has embedded _unsafe_anonymous_host field
     _misc_is_contended                        = 1 << 
(_misc_kind_field_size + 4),  // marked with contended annotation
...

At the very least this is a merge conflict that loom will need to deal 
with and it would help to know about in advance (Alan normally does the 
merges).

thanks,

Chris

On 4/21/20 1:12 PM, coleen.phillimore at oracle.com wrote:
> Summary: moved fields around and some constant fields into ConstantPool
>
> This is a simple change except that I moved some constant fields from 
> InstanceKlass into the constant pool so they can be shared read-only 
> in the CDS archive.  There are associated repercussions in SA and 
> JVMCI, so please look at these changes.  Also moved similarly sized 
> fields together in the class so there's less likelihood of introducing 
> gaps in future InstanceKlass changes.
>
> InstanceKlass is reduced from 544 to 520 bytes in a simple Hello World 
> class.
>
> open webrev at http://cr.openjdk.java.net/~coleenp/2020/8238048.01/webrev
> bug link https://bugs.openjdk.java.net/browse/JDK-8238048
>
> Tested with tier1-6.
>
> Thanks,
> Coleen
>
>