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8065618: C2 RA incorrectly removes kill projections

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Don't remove KILL projections if their "defining" nodes have SCMemProj projection (memory side effects).

Reviewed-by: iveresov
This commit is contained in:
Vladimir Kozlov 2014-11-21 17:17:41 -08:00
parent 585ca822b8
commit f36e847523
1 changed files with 16 additions and 0 deletions
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16
hotspot/src/share/vm/opto/ifg.cpp
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@ -527,6 +527,22 @@ bool PhaseChaitin::remove_node_if_not_used(Block* b, uint location, Node* n, uin
Node* def = n->in(0);
if (!n->is_Proj() ||
(_lrg_map.live_range_id(def) && !liveout->member(_lrg_map.live_range_id(def)))) {
if (n->is_MachProj()) {
// Don't remove KILL projections if their "defining" nodes have
// memory effects (have SCMemProj projection node) -
// they are not dead even when their result is not used.
// For example, compareAndSwapL (and other CAS) and EncodeISOArray nodes.
// The method add_input_to_liveout() keeps such nodes alive (put them on liveout list)
// when it sees SCMemProj node in a block. Unfortunately SCMemProj node could be placed
// in block in such order that KILL MachProj nodes are processed first.
uint cnt = def->outcnt();
for (uint i = 0; i < cnt; i++) {
Node* proj = def->raw_out(i);
if (proj->Opcode() == Op_SCMemProj) {
return false;
}
}
}
b->remove_node(location);
LRG& lrg = lrgs(lid);
if (lrg._def == n) {