[lworld] RFR: 8279624: [lworld] interpreter should avoid value copies in withfield when possible [v2]

[Frederic Parain]

> Please review this small change to reduce the number of copies the interpreter does when executing the withfield bytecode.
> If the new value of the field to be updated is identical to the old value of the field, the interpreter simply returns the original value instance instead of creating a new copy.
> This change removes more than 8K value copies when running the hotspot_valhalla test suite.
> 
> Tested with Mach5, tiers 1 to 3.
> 
> Thank you
> 
> Fred

Frederic Parain has updated the pull request incrementally with one additional commit since the last revision:

  Add support for floating point fields

-------------

Changes:
  - all: https://git.openjdk.java.net/valhalla/pull/595/files
  - new: https://git.openjdk.java.net/valhalla/pull/595/files/e89b1cda..82e9d6f2

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=valhalla&pr=595&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=valhalla&pr=595&range=00-01

  Stats: 6 lines in 1 file changed: 6 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/595.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/595/head:pull/595

PR: https://git.openjdk.java.net/valhalla/pull/595