hg: jdk/sandbox: 8249605: C2: assert(no_dead_loop) failed: dead loop detected

[chris.hegarty at oracle.com]

Changeset: 6565fb0907fa
Author:    chagedorn
Date:      2020-08-03 09:21 +0200
URL:       https://hg.openjdk.java.net/jdk/sandbox/rev/6565fb0907fa

8249605: C2: assert(no_dead_loop) failed: dead loop detected
Summary: Fixed dead loop detection in PhiNode::Ideal() to additionally account for dead MergeMemNodes
Reviewed-by: kvn, thartmann

! src/hotspot/share/opto/cfgnode.cpp
+ test/hotspot/jtreg/compiler/c2/TestDeadPhiMergeMemLoop.java