RFR: 8373343: C2: verify AddP base input only set for heap addresses [v3]

[Roland Westrelin]

> The base input of `AddP` is expected to only be set for heap accesses
> but I noticed some inconsistencies so I added an assert in the `AddP`
> constructor and fixed issues that it caught. AFAFICT, the
> inconsistencies shouldn't create issues.

Roland Westrelin has updated the pull request incrementally with one additional commit since the last revision:

  review

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/28769/files
  - new: https://git.openjdk.org/jdk/pull/28769/files/38eb3b3f..007e73cd

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28769&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28769&range=01-02

  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/28769.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28769/head:pull/28769

PR: https://git.openjdk.org/jdk/pull/28769