[jdk16] RFR: 8259227: C2 crashes with SIGFPE due to a division that floats above its zero check [v2]

[Christian Hagedorn]

> This bug is very similar to [JDK-8257822](https://bugs.openjdk.java.net/browse/JDK-8257822). In this testcase, a `Div` node has no longer its zero check as direct control input and is later moved before the zero check by `IfNode::dominated_by()` which updates all data nodes to a dominating `If` (in JDK-8257822 it was done by `PhaseIdealLoop::dominated_by()`) .
> 
> I suggest to use the same fix for `IfNode::dominated_by()` as for `PhaseIdealLoop::dominated_by()` in JDK-8257822 to only move data nodes to the dominating `If` if it is not a `Div` or `Mod` node that could have a zero divisor (i.e. a zero check).
> 
> Thanks,
> Christian

Christian Hagedorn has updated the pull request incrementally with one additional commit since the last revision:

  
  
  Add additional runs without fixed seed

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

Changes:
  - all: https://git.openjdk.java.net/jdk16/pull/89/files
  - new: https://git.openjdk.java.net/jdk16/pull/89/files/4273fcfb..461681a6

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk16&pr=89&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk16&pr=89&range=00-01

  Stats: 7 lines in 2 files changed: 6 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk16/pull/89.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk16 pull/89/head:pull/89

PR: https://git.openjdk.java.net/jdk16/pull/89