RFR: 8270886: Crash in PhaseIdealLoop::verify_strip_mined_scheduling [v2]

[Roland Westrelin]

> The crash occurs because an OuterStripMinedLoopEnd has only a single
> projection. The root cause is that an IfNode has a single
> projection. When the condition of that If constant folds, the IfNode
> ends up with no use which causes it to be removed. The
> OuterStripMinedLoopEnd projection is removed as a consequence.
> 
> When the If is constructed, it does have 2 projections. One of the
> projections lead to an infinite loop. That infinite loop has a
> safepoint node that's input to the Root node. When
> remove_root_to_sfpts_edges() executes in Compile::Optimize(), that
> edge is removed. But because PhaseRenumberLive runs next (a subclass
> of PhaseRemoveUseless), the infinite loop is removed.
> 
> The fix is to simply move the call to remove_root_to_sfpts_edges()
> after PhaseRemoveUseless.

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

  review

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4911/files
  - new: https://git.openjdk.java.net/jdk/pull/4911/files/92b480a1..93d04625

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4911&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4911&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4911.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4911/head:pull/4911

PR: https://git.openjdk.java.net/jdk/pull/4911