RFR (M) Close alignment gaps in InstanceKlass

[coleen.phillimore at oracle.com]

On 4/21/20 4:41 PM, Chris Plummer wrote:
> 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).

It looks like there are other changes in loom that motivated changing it 
like this.  Why is misc_kind_field_size = 0?

Did loom add more misc_flags ?  It turns out that there are plenty of 
available flags in the access_flags if more are needed.

Thank you for looking at the SA changes.

Coelen
>
> 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
>>
>>
>