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6701887: JDK7 server VM in endless loop in Node::dominates

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The method Node::dominates loops in the dead code which does not have a Region node.

Reviewed-by: jrose, never
This commit is contained in:
Vladimir Kozlov 2008-05-15 22:43:11 -07:00
parent 9bcba384cb
commit 60c74ba115
3 changed files with 23 additions and 15 deletions
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3
hotspot/src/share/vm/opto/c2_globals.hpp
View File

@ -390,5 +390,8 @@
\
product(intx, MaxLabelRootDepth, 1100, \
"Maximum times call Label_Root to prevent stack overflow") \
\
diagnostic(intx, DominatorSearchLimit, 1000, \
"Iterations limit in Node::dominates") \
C2_FLAGS(DECLARE_DEVELOPER_FLAG, DECLARE_PD_DEVELOPER_FLAG, DECLARE_PRODUCT_FLAG, DECLARE_PD_PRODUCT_FLAG, DECLARE_DIAGNOSTIC_FLAG, DECLARE_NOTPRODUCT_FLAG)

15
hotspot/src/share/vm/opto/memnode.cpp
View File

@ -256,7 +256,7 @@ bool MemNode::all_controls_dominate(Node* dom, Node* sub) {
if (dom == NULL || dom->is_top())
return false; // Conservative answer for dead code
if (dom->is_Start() || dom->is_Root() || dom == sub)
if (dom->is_Con() || dom->is_Start() || dom->is_Root() || dom == sub)
return true;
// 'dom' dominates 'sub' if its control edge and control edges
@ -298,7 +298,7 @@ bool MemNode::all_controls_dominate(Node* dom, Node* sub) {
return false; // Conservative answer for dead code
assert(n->is_CFG(), "expecting control");
}
if (n->is_Start() || n->is_Root()) {
if (n->is_Con() || n->is_Start() || n->is_Root()) {
only_dominating_controls = true;
} else if (n->is_CFG()) {
if (n->dominates(sub, nlist))
@ -308,12 +308,11 @@ bool MemNode::all_controls_dominate(Node* dom, Node* sub) {
} else {
// First, own control edge.
Node* m = n->find_exact_control(n->in(0));
if (m == NULL)
continue;
if (m->is_top())
return false; // Conservative answer for dead code
dom_list.push(m);
if (m != NULL) {
if (m->is_top())
return false; // Conservative answer for dead code
dom_list.push(m);
}
// Now, the rest of edges.
uint cnt = n->req();
for (uint i = 1; i < cnt; i++) {

20
hotspot/src/share/vm/opto/node.cpp
View File

@ -1043,6 +1043,9 @@ bool Node::dominates(Node* sub, Node_List &nlist) {
assert(this->is_CFG(), "expecting control");
assert(sub != NULL && sub->is_CFG(), "expecting control");
// detect dead cycle without regions
int iterations_without_region_limit = DominatorSearchLimit;
Node* orig_sub = sub;
nlist.clear();
bool this_dominates = false;
@ -1057,6 +1060,7 @@ bool Node::dominates(Node* sub, Node_List &nlist) {
// Region nodes were visited. Continue walk up to Start or Root
// to make sure that it did not walk in a cycle.
this_dominates = true; // first time meet
iterations_without_region_limit = DominatorSearchLimit; // Reset
} else {
return false; // already met before: walk in a cycle
}
@ -1069,19 +1073,20 @@ bool Node::dominates(Node* sub, Node_List &nlist) {
return false; // Conservative answer for dead code
if (sub == up && sub->is_Loop()) {
up = sub->in(0); // in(LoopNode::EntryControl);
} else if (sub == up && sub->is_Region()) {
up = sub->in(1); // in(LoopNode::EntryControl);
} else if (sub == up && sub->is_Region() && sub->req() == 3) {
iterations_without_region_limit = DominatorSearchLimit; // Reset
uint i = 1;
if (nlist.size() == 0) {
uint size = nlist.size();
if (size == 0) {
// No Region nodes (except Loops) were visited before.
// Take first valid path on the way up to 'this'.
} else if (nlist.at(nlist.size() - 1) == sub) {
} else if (nlist.at(size - 1) == sub) {
// This Region node was just visited. Take other path.
i = region_input + 1;
nlist.pop();
} else {
// Was this Region node visited before?
uint size = nlist.size();
for (uint j = 0; j < size; j++) {
if (nlist.at(j) == sub) {
return false; // The Region node was visited before. Give up.
@ -1104,8 +1109,9 @@ bool Node::dominates(Node* sub, Node_List &nlist) {
}
if (sub == up)
return false; // some kind of tight cycle
if (orig_sub == up)
return false; // walk in a cycle
if (--iterations_without_region_limit < 0)
return false; // dead cycle
sub = up;
}