Make scheduler handle floating non-naked loops.

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

Review URL: https://codereview.chromium.org/706123003

Cr-Commit-Position: refs/heads/master@{#25217}
git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@25217 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/compiler/scheduler.cc

@@ -685,7 +685,7 @@ class SpecialRPONumberer : public ZoneObject {
     stack_.resize(schedule_->BasicBlockCount() - previous_block_count_);
     previous_block_count_ = schedule_->BasicBlockCount();
     int stack_depth = Push(stack_, 0, entry, kBlockUnvisited1);
-    int num_loops = 0;
+    int num_loops = static_cast<int>(loops_.size());
 
     while (stack_depth > 0) {
       int current = stack_depth - 1;
@@ -717,7 +717,7 @@ class SpecialRPONumberer : public ZoneObject {
     }
 
     // If no loops were encountered, then the order we computed was correct.
-    if (num_loops != 0) {
+    if (num_loops > static_cast<int>(loops_.size())) {
       // Otherwise, compute the loop information from the backedges in order
       // to perform a traversal that groups loop bodies together.
       ComputeLoopInfo(stack_, num_loops, &backedges_);
@@ -725,7 +725,7 @@ class SpecialRPONumberer : public ZoneObject {
       // Initialize the "loop stack". Note the entry could be a loop header.
       LoopInfo* loop =
           HasLoopNumber(entry) ? &loops_[GetLoopNumber(entry)] : NULL;
-      order = NULL;
+      order = insert_after;
 
       // Perform an iterative post-order traversal, visiting loop bodies before
       // edges that lead out of loops. Visits each block once, but linking loop
@@ -737,7 +737,7 @@ class SpecialRPONumberer : public ZoneObject {
         BasicBlock* block = frame->block;
         BasicBlock* succ = NULL;
 
-        if (frame->index < block->SuccessorCount()) {
+        if (block != end && frame->index < block->SuccessorCount()) {
           // Process the next normal successor.
           succ = block->SuccessorAt(frame->index++);
         } else if (HasLoopNumber(block)) {

test/cctest/compiler/test-scheduler.cc

@@ -1816,6 +1816,48 @@ TEST(NestedFloatingDiamonds) {
 }
 
 
+TEST(NestedFloatingDiamondWithLoop) {
+  HandleAndZoneScope scope;
+  Graph graph(scope.main_zone());
+  CommonOperatorBuilder common(scope.main_zone());
+  SimplifiedOperatorBuilder simplified(scope.main_zone());
+  MachineOperatorBuilder machine;
+
+  Node* start = graph.NewNode(common.Start(2));
+  graph.SetStart(start);
+
+  Node* p0 = graph.NewNode(common.Parameter(0), start);
+
+  Node* fv = graph.NewNode(common.Int32Constant(7));
+  Node* br = graph.NewNode(common.Branch(), p0, graph.start());
+  Node* t = graph.NewNode(common.IfTrue(), br);
+  Node* f = graph.NewNode(common.IfFalse(), br);
+
+  Node* loop = graph.NewNode(common.Loop(2), f, start);
+  Node* ind = graph.NewNode(common.Phi(kMachAnyTagged, 2), p0, p0, loop);
+
+  // TODO(mstarzinger): Make scheduler deal with non-empty loops here.
+  // Node* add = graph.NewNode(machine.IntAdd(), ind, fv);
+
+  Node* br1 = graph.NewNode(common.Branch(), ind, loop);
+  Node* t1 = graph.NewNode(common.IfTrue(), br1);
+  Node* f1 = graph.NewNode(common.IfFalse(), br1);
+
+  loop->ReplaceInput(1, t1);  // close loop.
+  ind->ReplaceInput(1, ind);  // close induction variable.
+
+  Node* m = graph.NewNode(common.Merge(2), t, f1);
+  Node* phi = graph.NewNode(common.Phi(kMachAnyTagged, 2), fv, ind, m);
+
+  Node* ret = graph.NewNode(common.Return(), phi, start, start);
+  Node* end = graph.NewNode(common.End(), ret, start);
+
+  graph.SetEnd(end);
+
+  ComputeAndVerifySchedule(19, &graph);
+}
+
+
 TEST(LoopedFloatingDiamond1) {
   HandleAndZoneScope scope;
   Graph graph(scope.main_zone());