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comparison src/share/vm/opto/node.cpp @ 155:723be81c1212

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6701887: JDK7 server VM in endless loop in Node::dominates Summary: The method Node::dominates loops in the dead code which does not have a Region node. Reviewed-by: jrose, never
author kvn
date Thu, 15 May 2008 22:43:11 -0700
parents ec73d88d5b43
children 885ed790ecf0
comparison
equal deleted inserted replaced
154:09c2ba680204 155:723be81c1212
1041 // Check if 'this' control node dominates or equal to 'sub' control node. 1041 // Check if 'this' control node dominates or equal to 'sub' control node.
1042 bool Node::dominates(Node* sub, Node_List &nlist) { 1042 bool Node::dominates(Node* sub, Node_List &nlist) {
1043 assert(this->is_CFG(), "expecting control"); 1043 assert(this->is_CFG(), "expecting control");
1044 assert(sub != NULL && sub->is_CFG(), "expecting control"); 1044 assert(sub != NULL && sub->is_CFG(), "expecting control");
1045 1045
1046 // detect dead cycle without regions
1047 int iterations_without_region_limit = DominatorSearchLimit;
1048
1046 Node* orig_sub = sub; 1049 Node* orig_sub = sub;
1047 nlist.clear(); 1050 nlist.clear();
1048 bool this_dominates = false; 1051 bool this_dominates = false;
1049 uint region_input = 0; 1052 uint region_input = 0;
1050 while (sub != NULL) { // walk 'sub' up the chain to 'this' 1053 while (sub != NULL) { // walk 'sub' up the chain to 'this'
1055 return true; 1058 return true;
1056 } else if (!this_dominates) { 1059 } else if (!this_dominates) {
1057 // Region nodes were visited. Continue walk up to Start or Root 1060 // Region nodes were visited. Continue walk up to Start or Root
1058 // to make sure that it did not walk in a cycle. 1061 // to make sure that it did not walk in a cycle.
1059 this_dominates = true; // first time meet 1062 this_dominates = true; // first time meet
1063 iterations_without_region_limit = DominatorSearchLimit; // Reset
1060 } else { 1064 } else {
1061 return false; // already met before: walk in a cycle 1065 return false; // already met before: walk in a cycle
1062 } 1066 }
1063 } 1067 }
1064 if (sub->is_Start() || sub->is_Root()) 1068 if (sub->is_Start() || sub->is_Root())
1067 Node* up = sub->find_exact_control(sub->in(0)); 1071 Node* up = sub->find_exact_control(sub->in(0));
1068 if (up == NULL || up->is_top()) 1072 if (up == NULL || up->is_top())
1069 return false; // Conservative answer for dead code 1073 return false; // Conservative answer for dead code
1070 1074
1071 if (sub == up && sub->is_Loop()) { 1075 if (sub == up && sub->is_Loop()) {
1072 up = sub->in(0); // in(LoopNode::EntryControl); 1076 up = sub->in(1); // in(LoopNode::EntryControl);
1073 } else if (sub == up && sub->is_Region()) { 1077 } else if (sub == up && sub->is_Region() && sub->req() == 3) {
1078 iterations_without_region_limit = DominatorSearchLimit; // Reset
1074 uint i = 1; 1079 uint i = 1;
1075 if (nlist.size() == 0) { 1080 uint size = nlist.size();
1081 if (size == 0) {
1076 // No Region nodes (except Loops) were visited before. 1082 // No Region nodes (except Loops) were visited before.
1077 // Take first valid path on the way up to 'this'. 1083 // Take first valid path on the way up to 'this'.
1078 } else if (nlist.at(nlist.size() - 1) == sub) { 1084 } else if (nlist.at(size - 1) == sub) {
1079 // This Region node was just visited. Take other path. 1085 // This Region node was just visited. Take other path.
1080 i = region_input + 1; 1086 i = region_input + 1;
1081 nlist.pop(); 1087 nlist.pop();
1082 } else { 1088 } else {
1083 // Was this Region node visited before? 1089 // Was this Region node visited before?
1084 uint size = nlist.size();
1085 for (uint j = 0; j < size; j++) { 1090 for (uint j = 0; j < size; j++) {
1086 if (nlist.at(j) == sub) { 1091 if (nlist.at(j) == sub) {
1087 return false; // The Region node was visited before. Give up. 1092 return false; // The Region node was visited before. Give up.
1088 } 1093 }
1089 } 1094 }
1102 region_input = i; 1107 region_input = i;
1103 } 1108 }
1104 } 1109 }
1105 if (sub == up) 1110 if (sub == up)
1106 return false; // some kind of tight cycle 1111 return false; // some kind of tight cycle
1107 if (orig_sub == up) 1112
1108 return false; // walk in a cycle 1113 if (--iterations_without_region_limit < 0)
1114 return false; // dead cycle
1109 1115
1110 sub = up; 1116 sub = up;
1111 } 1117 }
1112 return false; 1118 return false;
1113 } 1119 }