[lworld] RFR: 8375196: [lworld] TestArrays triggers assert in LRG::set_num_regs [v2]

[Quan Anh Mai]

> Hi,
> 
> The issue is that `PhaseMacroExpand::value_from_mem_phi` does not take into consideration flat arrays, so it incorrectly returns the whole object for a load from one of its fields. This results in a byte `Phi` with an input being an `oop`, triggering the assert during `LRG::set_num_regs` because the size of a `Phi` and its input are different.
> 
> Please take a look and leave your reviews, thanks a lot.

Quan Anh Mai has updated the pull request incrementally with one additional commit since the last revision:

  Add reminder at LibraryCallKit::inline_newArray

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

Changes:
  - all: https://git.openjdk.org/valhalla/pull/1909/files
  - new: https://git.openjdk.org/valhalla/pull/1909/files/718c0d02..45b98d92

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=1909&range=01
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=1909&range=00-01

  Stats: 3 lines in 1 file changed: 3 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/valhalla/pull/1909.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1909/head:pull/1909

PR: https://git.openjdk.org/valhalla/pull/1909