[jdk16] RFR: 8258790: C2: Crash on empty macro node list [v2]

[Vladimir Ivanov]

> The fix for 8257624 is incomplete: it doesn't cover the case when macro node array becomes empty as a result of multiple nodes removal. In such case, the out-of-bounds access still takes place (at index "-1"). 
> 
> Proposed fix is to adjust the index before performing "i > 0" check.    
> 
> Testing:
> - [x] failing tests
> - [ ] hs-precheckin-comp, hs-tier1, hs-tier2

Vladimir Ivanov has updated the pull request incrementally with one additional commit since the last revision:

  Reformat i-1 => i - 1

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

Changes:
  - all: https://git.openjdk.java.net/jdk16/pull/56/files
  - new: https://git.openjdk.java.net/jdk16/pull/56/files/174e9889..b94ba8f3

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk16&pr=56&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk16&pr=56&range=00-01

  Stats: 4 lines in 1 file changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk16/pull/56.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk16 pull/56/head:pull/56

PR: https://git.openjdk.java.net/jdk16/pull/56