1.1 --- a/src/share/vm/opto/node.cpp Tue May 20 06:32:58 2008 -0700
1.2 +++ b/src/share/vm/opto/node.cpp Wed May 21 10:45:07 2008 -0700
1.3 @@ -1049,51 +1049,80 @@
1.4 Node* orig_sub = sub;
1.5 nlist.clear();
1.6 bool this_dominates = false;
1.7 - uint region_input = 0;
1.8 + bool result = false; // Conservative answer
1.9 +
1.10 while (sub != NULL) { // walk 'sub' up the chain to 'this'
1.11 if (sub == this) {
1.12 if (nlist.size() == 0) {
1.13 // No Region nodes except loops were visited before and the EntryControl
1.14 // path was taken for loops: it did not walk in a cycle.
1.15 - return true;
1.16 - } else if (!this_dominates) {
1.17 + result = true;
1.18 + break;
1.19 + } else if (this_dominates) {
1.20 + result = false; // already met before: walk in a cycle
1.21 + break;
1.22 + } else {
1.23 // Region nodes were visited. Continue walk up to Start or Root
1.24 // to make sure that it did not walk in a cycle.
1.25 this_dominates = true; // first time meet
1.26 iterations_without_region_limit = DominatorSearchLimit; // Reset
1.27 - } else {
1.28 - return false; // already met before: walk in a cycle
1.29 - }
1.30 + }
1.31 }
1.32 - if (sub->is_Start() || sub->is_Root())
1.33 - return this_dominates;
1.34 + if (sub->is_Start() || sub->is_Root()) {
1.35 + result = this_dominates;
1.36 + break;
1.37 + }
1.38 + Node* up = sub->find_exact_control(sub->in(0));
1.39 + if (up == NULL || up->is_top()) {
1.40 + result = false; // Conservative answer for dead code
1.41 + break;
1.42 + }
1.43 + if (sub == up && (sub->is_Loop() || sub->is_Region() && sub->req() != 3)) {
1.44 + // Take first valid path on the way up to 'this'.
1.45 + up = sub->in(1); // in(LoopNode::EntryControl);
1.46 + } else if (sub == up && sub->is_Region()) {
1.47 + assert(sub->req() == 3, "sanity");
1.48 + iterations_without_region_limit = DominatorSearchLimit; // Reset
1.49
1.50 - Node* up = sub->find_exact_control(sub->in(0));
1.51 - if (up == NULL || up->is_top())
1.52 - return false; // Conservative answer for dead code
1.53 -
1.54 - if (sub == up && sub->is_Loop()) {
1.55 - up = sub->in(1); // in(LoopNode::EntryControl);
1.56 - } else if (sub == up && sub->is_Region() && sub->req() == 3) {
1.57 - iterations_without_region_limit = DominatorSearchLimit; // Reset
1.58 + // Try both paths for such Regions.
1.59 + // It is not accurate without regions dominating information.
1.60 + // With such information the other path should be checked for
1.61 + // the most dominating Region which was visited before.
1.62 + bool region_was_visited_before = false;
1.63 uint i = 1;
1.64 uint size = nlist.size();
1.65 if (size == 0) {
1.66 - // No Region nodes (except Loops) were visited before.
1.67 + // No such Region nodes were visited before.
1.68 // Take first valid path on the way up to 'this'.
1.69 - } else if (nlist.at(size - 1) == sub) {
1.70 - // This Region node was just visited. Take other path.
1.71 - i = region_input + 1;
1.72 - nlist.pop();
1.73 } else {
1.74 // Was this Region node visited before?
1.75 - for (uint j = 0; j < size; j++) {
1.76 - if (nlist.at(j) == sub) {
1.77 - return false; // The Region node was visited before. Give up.
1.78 + intptr_t ni;
1.79 + int j = size - 1;
1.80 + for (; j >= 0; j--) {
1.81 + ni = (intptr_t)nlist.at(j);
1.82 + if ((Node*)(ni & ~1) == sub) {
1.83 + if ((ni & 1) != 0) {
1.84 + break; // Visited 2 paths. Give up.
1.85 + } else {
1.86 + // The Region node was visited before only once.
1.87 + nlist.remove(j);
1.88 + region_was_visited_before = true;
1.89 + for (; i < sub->req(); i++) {
1.90 + Node* in = sub->in(i);
1.91 + if (in != NULL && !in->is_top() && in != sub) {
1.92 + break;
1.93 + }
1.94 + }
1.95 + i++; // Take other path.
1.96 + break;
1.97 + }
1.98 }
1.99 }
1.100 + if (j >= 0 && (ni & 1) != 0) {
1.101 + result = false; // Visited 2 paths. Give up.
1.102 + break;
1.103 + }
1.104 // The Region node was not visited before.
1.105 - // Take first valid path on the way up to 'this'.
1.106 }
1.107 for (; i < sub->req(); i++) {
1.108 Node* in = sub->in(i);
1.109 @@ -1102,20 +1131,26 @@
1.110 }
1.111 }
1.112 if (i < sub->req()) {
1.113 - nlist.push(sub);
1.114 up = sub->in(i);
1.115 - region_input = i;
1.116 + if (region_was_visited_before && sub != up) {
1.117 + // Set 0 bit to indicate that both paths were taken.
1.118 + nlist.push((Node*)((intptr_t)sub + 1));
1.119 + } else {
1.120 + nlist.push(sub);
1.121 + }
1.122 }
1.123 }
1.124 - if (sub == up)
1.125 - return false; // some kind of tight cycle
1.126 -
1.127 - if (--iterations_without_region_limit < 0)
1.128 - return false; // dead cycle
1.129 -
1.130 + if (sub == up) {
1.131 + result = false; // some kind of tight cycle
1.132 + break;
1.133 + }
1.134 + if (--iterations_without_region_limit < 0) {
1.135 + result = false; // dead cycle
1.136 + break;
1.137 + }
1.138 sub = up;
1.139 }
1.140 - return false;
1.141 + return result;
1.142 }
1.143
1.144 //------------------------------remove_dead_region-----------------------------
