Fix loop information computation for floating loops.

R=jarin@chromium.org
TEST=cctest/test-scheduler/LoopedFloatingDiamond3

Review URL: https://codereview.chromium.org/726953002

Cr-Commit-Position: refs/heads/master@{#25399}

src/compiler/scheduler.cc

@@ -763,7 +763,7 @@ class SpecialRPONumberer : public ZoneObject {
               static_cast<int>(frame->index - block->SuccessorCount());
           LoopInfo* info = &loops_[GetLoopNumber(block)];
           DCHECK(loop != info);
-          if (info->outgoing != NULL &&
+          if (block != entry && info->outgoing != NULL &&
               outgoing_index < info->outgoing->length()) {
             succ = info->outgoing->at(outgoing_index);
             frame->index++;
@@ -871,6 +871,15 @@ class SpecialRPONumberer : public ZoneObject {
   // Computes loop membership from the backedges of the control flow graph.
   void ComputeLoopInfo(ZoneVector<SpecialRPOStackFrame>& queue,
                        size_t num_loops, ZoneList<Backedge>* backedges) {
+    // Extend existing loop membership vectors.
+    for (LoopInfo& loop : loops_) {
+      BitVector* new_members = new (zone_)
+          BitVector(static_cast<int>(schedule_->BasicBlockCount()), zone_);
+      new_members->CopyFrom(*loop.members);
+      loop.members = new_members;
+    }
+
+    // Extend loop information vector.
     loops_.resize(num_loops, LoopInfo());
 
     // Compute loop membership starting from backedges.

test/cctest/compiler/test-scheduler.cc

@@ -1810,7 +1810,6 @@ TEST(NestedFloatingDiamondWithLoop) {
   HandleAndZoneScope scope;
   Graph graph(scope.main_zone());
   CommonOperatorBuilder common(scope.main_zone());
-  SimplifiedOperatorBuilder simplified(scope.main_zone());
 
   Node* start = graph.NewNode(common.Start(2));
   graph.SetStart(start);
@@ -1849,7 +1848,6 @@ TEST(LoopedFloatingDiamond1) {
   HandleAndZoneScope scope;
   Graph graph(scope.main_zone());
   CommonOperatorBuilder common(scope.main_zone());
-  SimplifiedOperatorBuilder simplified(scope.main_zone());
 
   Node* start = graph.NewNode(common.Start(2));
   graph.SetStart(start);
@@ -1887,7 +1885,6 @@ TEST(LoopedFloatingDiamond2) {
   HandleAndZoneScope scope;
   Graph graph(scope.main_zone());
   CommonOperatorBuilder common(scope.main_zone());
-  SimplifiedOperatorBuilder simplified(scope.main_zone());
 
   Node* start = graph.NewNode(common.Start(2));
   graph.SetStart(start);
@@ -1922,11 +1919,60 @@ TEST(LoopedFloatingDiamond2) {
 }
 
 
+TEST(LoopedFloatingDiamond3) {
+  HandleAndZoneScope scope;
+  Graph graph(scope.main_zone());
+  CommonOperatorBuilder common(scope.main_zone());
+
+  Node* start = graph.NewNode(common.Start(2));
+  graph.SetStart(start);
+
+  Node* p0 = graph.NewNode(common.Parameter(0), start);
+
+  Node* c = graph.NewNode(common.Int32Constant(7));
+  Node* loop = graph.NewNode(common.Loop(2), start, start);
+  Node* ind = graph.NewNode(common.Phi(kMachAnyTagged, 2), p0, p0, loop);
+
+  Node* br1 = graph.NewNode(common.Branch(), p0, graph.start());
+  Node* t1 = graph.NewNode(common.IfTrue(), br1);
+  Node* f1 = graph.NewNode(common.IfFalse(), br1);
+
+  Node* loop1 = graph.NewNode(common.Loop(2), t1, start);
+  Node* ind1 = graph.NewNode(common.Phi(kMachAnyTagged, 2), p0, p0, loop);
+
+  Node* add1 = graph.NewNode(&kIntAdd, ind1, c);
+  Node* br2 = graph.NewNode(common.Branch(), add1, loop1);
+  Node* t2 = graph.NewNode(common.IfTrue(), br2);
+  Node* f2 = graph.NewNode(common.IfFalse(), br2);
+
+  loop1->ReplaceInput(1, t2);   // close inner loop.
+  ind1->ReplaceInput(1, ind1);  // close inner induction variable.
+
+  Node* m1 = graph.NewNode(common.Merge(2), f1, f2);
+  Node* phi1 = graph.NewNode(common.Phi(kMachAnyTagged, 2), c, ind1, m1);
+
+  Node* add = graph.NewNode(&kIntAdd, ind, phi1);
+
+  Node* br = graph.NewNode(common.Branch(), add, loop);
+  Node* t = graph.NewNode(common.IfTrue(), br);
+  Node* f = graph.NewNode(common.IfFalse(), br);
+
+  loop->ReplaceInput(1, t);   // close loop.
+  ind->ReplaceInput(1, add);  // close induction variable.
+
+  Node* ret = graph.NewNode(common.Return(), ind, start, f);
+  Node* end = graph.NewNode(common.End(), ret, f);
+
+  graph.SetEnd(end);
+
+  ComputeAndVerifySchedule(28, &graph);
+}
+
+
 TEST(PhisPushedDownToDifferentBranches) {
   HandleAndZoneScope scope;
   Graph graph(scope.main_zone());
   CommonOperatorBuilder common(scope.main_zone());
-  SimplifiedOperatorBuilder simplified(scope.main_zone());
 
   Node* start = graph.NewNode(common.Start(2));
   graph.SetStart(start);