JDK-8162496 : missing precedence edge for anti_dependence
  • Type: Bug
  • Component: hotspot
  • Sub-Component: compiler
  • Affected Version: 8u92,9
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • OS: generic
  • CPU: generic
  • Submitted: 2016-07-25
  • Updated: 2017-11-29
  • Resolved: 2016-08-18
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JDK 8 JDK 9
8u152Fixed 9 b137Fixed
Related Reports
Relates :  
JDK-8157306 - Random infrequent null pointer exceptions in javac
Description
JDK-8157306 original changes added assert for anti_dependence edges after GCM:
http://cr.openjdk.java.net/~aph/8157306.1/

Unfortunately it triggered more failures than fixed by JDK-8157306 changes.
Since that fix was critical for AARCH 64 project we decided to push it without assert and file this bug which will fix the rest of failures.

We may need to backport this and 8157306 fixes.

Failure:
#  Internal Error (hotspot/src/share/vm/opto/gcm.cpp:788), pid=14456, tid=28
#  assert(store->find_edge(load) != -1) failed: missing precedence edge

jtreg should be run with -vmoptions:'-Xcomp' to reproduce failures.
Comments
No new tests were added since the problem showed with existing Hotspot jtreg tests
07-09-2016
Fix in addition to assert: src/share/vm/opto/lcm.cpp @@ -437,6 +437,18 @@ latency_from_uses(nul_chk); latency_from_uses(best); + + // insert anti-dependences to defs in this block + if (! best->needs_anti_dependence_check()) { + for (uint k = 1; k < block->number_of_nodes(); k++) { + Node *n = block->get_node(k); + if (n->needs_anti_dependence_check() && + n->in(LoadNode::Memory) == best->in(StoreNode::Memory)) { + // Found anti-dependent load + insert_anti_dependences(block, n); + } + } + } }
06-08-2016
9-defer-SQE-ok: agreed on deferral reason
27-07-2016
9-defer-request: This failure only shows up with verification code that is currently not enabled. It's not clear if the failures are even "real" problems or if the verification code needs to be fixed because it's too strong. There are no known related problems.
26-07-2016
ILW = Potential problem, only shows up with currently not enabled verification code, no workaround = MLH = P4
26-07-2016