RFR: 8361702: C2: assert(is_dominator(compute_early_ctrl(limit, limit_ctrl), pre_end)) failed: node pinned on loop exit test? [v2]

[Roland Westrelin]

> A node in a pre loop only has uses out of the loop dominated by the
> loop exit. `PhaseIdealLoop::try_sink_out_of_loop()` sets its control
> to the loop exit projection. A range check in the main loop has this
> node as input (through a chain of some other nodes). Range check
> elimination needs to update the exit condition of the pre loop with an
> expression that depends on the node pinned on its exit: that's
> impossible and the assert fires. This is a variant of 8314024 (this
> one was for a node with uses out of the pre loop on multiple paths). I
> propose the same fix: leave the node with control in the pre loop in
> this case.

Roland Westrelin has updated the pull request incrementally with four additional commits since the last revision:

 - Update test/hotspot/jtreg/compiler/rangechecks/TestSunkRangeFromPreLoopRCE3.java
   
   Co-authored-by: Christian Hagedorn <christian.hagedorn at oracle.com>
 - Update test/hotspot/jtreg/compiler/rangechecks/TestSunkRangeFromPreLoopRCE2.java
   
   Co-authored-by: Christian Hagedorn <christian.hagedorn at oracle.com>
 - Update src/hotspot/share/opto/loopopts.cpp
   
   Co-authored-by: Christian Hagedorn <christian.hagedorn at oracle.com>
 - Update test/hotspot/jtreg/compiler/rangechecks/TestSunkRangeFromPreLoopRCE2.java
   
   Co-authored-by: Christian Hagedorn <christian.hagedorn at oracle.com>

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/26424/files
  - new: https://git.openjdk.org/jdk/pull/26424/files/8abae076..2140c98d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=26424&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26424&range=00-01

  Stats: 9 lines in 3 files changed: 3 ins; 6 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/26424.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26424/head:pull/26424

PR: https://git.openjdk.org/jdk/pull/26424