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8275326: C2: assert(no_dead_loop) failed: dead loop detected

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Reviewed-by: kvn, thartmann
This commit is contained in:
Christian Hagedorn 2021-12-01 08:24:59 +00:00
parent 349328c929
commit 70d5dffb4e
1 changed files with 13 additions and 8 deletions
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21
src/hotspot/share/opto/cfgnode.cpp
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@ -2272,13 +2272,13 @@ Node *PhiNode::Ideal(PhaseGVN *phase, bool can_reshape) {
// Phi(...MergeMem(m0, m1:AT1, m2:AT2)...) into
// MergeMem(Phi(...m0...), Phi:AT1(...m1...), Phi:AT2(...m2...))
PhaseIterGVN* igvn = phase->is_IterGVN();
assert(igvn != NULL, "sanity check");
Node* hook = new Node(1);
PhiNode* new_base = (PhiNode*) clone();
// Must eagerly register phis, since they participate in loops.
if (igvn) {
igvn->register_new_node_with_optimizer(new_base);
hook->add_req(new_base);
}
igvn->register_new_node_with_optimizer(new_base);
hook->add_req(new_base);
MergeMemNode* result = MergeMemNode::make(new_base);
for (uint i = 1; i < req(); ++i) {
Node *ii = in(i);
@ -2290,10 +2290,8 @@ Node *PhiNode::Ideal(PhaseGVN *phase, bool can_reshape) {
if (mms.is_empty()) {
Node* new_phi = new_base->slice_memory(mms.adr_type(phase->C));
made_new_phi = true;
if (igvn) {
igvn->register_new_node_with_optimizer(new_phi);
hook->add_req(new_phi);
}
igvn->register_new_node_with_optimizer(new_phi);
hook->add_req(new_phi);
mms.set_memory(new_phi);
}
Node* phi = mms.memory();
@ -2311,6 +2309,13 @@ Node *PhiNode::Ideal(PhaseGVN *phase, bool can_reshape) {
}
}
}
// Already replace this phi node to cut it off from the graph to not interfere in dead loop checks during the
// transformations of the new phi nodes below. Otherwise, we could wrongly conclude that there is no dead loop
// because we are finding this phi node again. Also set the type of the new MergeMem node in case we are also
// visiting it in the transformations below.
igvn->replace_node(this, result);
igvn->set_type(result, result->bottom_type());
// now transform the new nodes, and return the mergemem
for (MergeMemStream mms(result); mms.next_non_empty(); ) {
Node* phi = mms.memory();