JDK-6515373 : Self referenced phi causes assert in falltrough case in RegionNode::Ideal
  • Type: Bug
  • Component: hotspot
  • Sub-Component: compiler
  • Affected Version: 7
  • Priority: P2
  • Status: Resolved
  • Resolution: Fixed
  • OS: solaris_9
  • CPU: sparc
  • Submitted: 2007-01-19
  • Updated: 2010-04-03
  • Resolved: 2007-01-31
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JDK 6 JDK 7 Other
6u2Fixed 7Fixed hs10Fixed
Related Reports
Relates :  
JDK-5067347 - dead code/loops checks and elimination.
Description
Self referenced phi causes assert in falltrough case in RegionNode::Ideal():

 assert(dead->outcnt() == 0 && !dead->is_top(), "node must be dead");

The stack looks like:

  [3] PhaseIterGVN::remove_dead_node()
  [4] PhaseIterGVN::subsume_node()
  [5] RegionNode::Ideal()
  [6] PhaseIterGVN::transform_old()
  [7] PhaseIterGVN::optimize

The ideal case has found a phi with a single input and wants to replace it. The single input is itself!

 2644   Phi     ===  2641  2644
Comments
SUGGESTED FIX Webrev: http://prt-web.sfbay.sun.com/net/prt-archiver.sfbay/data/archived_workspaces/main/c2_baseline/2007/20070122112609.kvn.6515373/workspace/webrevs/webrev-2007.01.22/index.html
22-01-2007
SUGGESTED FIX We should check if phi->in(1)==phi and kill it in this case.
19-01-2007
EVALUATION The assert is causes by this call where n == n->in(1): igv->subsume_node(n, n->in(1));
19-01-2007