[11u] RFR 8240795: [REDO] 8238384 CTW: C2 compilation fails with "assert(store != load->find_exact_control(load->in(0))) failed: dependence cycle found"

[Reingruber, Richard]

Hi,

I would like to downport JDK-8240795 to 11u as prerequisite for the downport of
JDK-8243670.

I need to be sponsored for this too, please.

Please review:
 
Original bug:
  https://bugs.openjdk.java.net/browse/JDK-8240795
  https://hg.openjdk.java.net/jdk/jdk/rev/993974f21271

11u webrev:
  http://cr.openjdk.java.net/~rrich/webrevs/8240795_11u_REDO__8238384_CTW__C2_compilation_fails_with__assert_dependence_cycle_found/webrev.0/
 
Modifications:

  The 2 hunks for loopnode.cpp were removed from the original patch. They do not
  apply because they are based on the enhancement 8238691 which has not been
  downported. These hunks introduced a bug which was fixed with 8252292. I don't
  intend to downport 8252292 but I have verified that the included test case
  succeeds even without it.

Testing:

test/hotspot/jtreg/compiler/escapeAnalysis/TestMissingAntiDependency.java
  - from 8252292
  - succeeds independently of the patch under review
  - will not be downported

test/hotspot/jtreg/compiler/escapeAnalysis/TestCopyOfBrokenAntiDependency.java
  - included in the patch under review
  - fails without patch (assertion "dependence cycle found")
  - succeeds with patch


CI testing @SAP: JCK and JTREG, also in Xcomp mode, SPECjvm2008, SPECjbb2015, Renaissance Suite,
SAP specific tests with fastdebug and release builds on all platforms
 
Thanks, Richard.