[lworld] RFR: 8255541: [lworld] Improve array layout checks in C2 compiled code [v3]

[Tobias Hartmann]

> C2 should use a single bit test of the layout helper value to check for flat/null-free inline type arrays. This is a prerequisite of JDK-8255046 which will then add support for checking the corresponding bits in the mark word instead.
> 
> Best regards,
> Tobias

Tobias Hartmann has updated the pull request incrementally with one additional commit since the last revision:

  Moved EnableValhalla check added to the wrong place

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

Changes:
  - all: https://git.openjdk.java.net/valhalla/pull/244/files
  - new: https://git.openjdk.java.net/valhalla/pull/244/files/8f38bb8f..d407a75b

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=valhalla&pr=244&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=valhalla&pr=244&range=01-02

  Stats: 6 lines in 1 file changed: 2 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/244.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/244/head:pull/244

PR: https://git.openjdk.java.net/valhalla/pull/244