RFR: 8251271: C2: Compile::_for_igvn list is corrupted after RenumberLiveNodes [v2]

[Nhat Nguyen]

> I'm following up on this thread http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2020-September/039910.html
> I'm clearing `for_igvn` before restoring as suggested by Xin

Nhat Nguyen has updated the pull request incrementally with one additional commit since the last revision:

  Clear for_igvn in PhaseRenumberLive

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/713/files
  - new: https://git.openjdk.java.net/jdk/pull/713/files/4ab0abc7..35835f81

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=713&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=713&range=00-01

  Stats: 10 lines in 2 files changed: 4 ins; 5 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/713.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/713/head:pull/713

PR: https://git.openjdk.java.net/jdk/pull/713