[lworld] RFR: 8376791: [lworld] C2 compilation hits assert(!not_flat || !is_flat()) failed: inconsistency [v3]

[Quan Anh Mai]

> Hi,
> 
> The issue is that we blindly assume that the vararg argument is a not flat and not null-free array. This misses 2 factors:
> 
> - With the introduction of nullable flat layouts, it is possible to flatten a default array allocation (e.g. `new Integer[4]`)
> - The node may have its own speculative type already, we need to make sure our optimistic guess does not contradict the existing speculation.
> 
> As a result, I changed the implementation to assume that the exact type is the default refined type of the declared parameter type.
> 
> Testing:
> 
> - [ ] tier1-4,valhalla-comp-stress, Linux-x64
> 
> Please kindly review, thanks a lot.

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

  Only for top-most method

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

Changes:
  - all: https://git.openjdk.org/valhalla/pull/2030/files
  - new: https://git.openjdk.org/valhalla/pull/2030/files/887017b3..b9b87af6

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=2030&range=02
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=2030&range=01-02

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/valhalla/pull/2030.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/2030/head:pull/2030

PR: https://git.openjdk.org/valhalla/pull/2030