RFR: JDK-8232069: Enable CDS even when UseCompressedClassPointers and/or UseCompressedOops are false

[Yumin Qi]

Hi,

    Please review fix:

    Bug: https://bugs.openjdk.java.net/browse/JDK-8232069

    Webrev:http://cr.openjdk.java.net/~minqi/8232069/webrev/

     Description: Currently CDS only works when using compressed Oops 
turned on, -XX:+UseCompressedOops (default), the fix is allowing CDS 
works with uncompressed oops and uncompressed class pointers. The 
contents of InstanceKlass::_fields are depending on UseCompressedOops 
and UseCompressedClassPointers on/off. There are three suggestions as 
described in bug description:

1. Remember the compression mode at CDS dump time. At runtime, disable 
CDS if the compression mode is changed.
2. Same as 1, but save more than one CDS archives in the JDK image. 
Choose the appropriate one at start-up
3. Recompute re-compute InstanceKlass::_fields at runtime.

The fix takes the first one, storing UseCompressedOops and 
UseCompressedClassPointers in shared archive. CDS is only allowed at 
runtime if the flags are consistent with the stored versions in archive.

  Testing: hs-tier1-2


   Thanks

   Yumin