RFR (M): 8004640: C2 assert failure in memnode.cpp: NULL+offs not RAW address?
vladimir.kozlov at oracle.com
Mon Mar 25 17:25:01 PDT 2013
IdealKit does not call transform() for raw address when generates post
barrier code and C2 type system does not accept such type.
AddPNode::Ideal() should be called to transform raw (NULL+offs) to
CastX2P(offs). We got NULL as base because cardmark byte_map_base is 0x0
which is valid value.
IdealKit delays transformations to avoid graph collapsing before it is
finished. But delaying logic is broken because during Parse phase
PhaseGVN::transform() does not replace old node with new transformed one.
Fix: always transform AddP nodes in IdealKit by calling _gvn.transform().
Clean delaying logic only to register new nodes for igvn and don't do
useless delayed transformations. Also remove is_IterGVN() checks since
IdealKit works only during Parse phase.
An other possible cause of the failure is to get dead nodes on IGVN
_worklist. I looked on recent changes and did some modifications. In
PhaseIdealLoop::build_and_optimize() moved dead nodes cleanup back after
build_loop_late(). Used replace_edge(in, NULL) in
remove_globally_dead_node() to cut all edges pointed to dead node and
did other rearrangements in that method.
Tested with compiler jtreg, ctw, jprt. Did additional testing with
GraphKit::byte_map_base_node() always returning null() with
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