Fix schedule for interleaved floating control by wiring one floating control structure per block.

src/compiler/scheduler.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <deque>
 #include <queue>
 
 #include "src/compiler/scheduler.h"
 
 #include "src/compiler/graph.h"
@@ skipping 620 matching lines @@
   if (!has_floating_control_) return false;
 
   Trace("Connecting floating control...\n");
 
   // Process blocks and instructions backwards to find and connect floating
   // control nodes into the control graph according to the block they were
   // scheduled into.
   int max = static_cast<int>(schedule_->rpo_order()->size());
   for (int i = max - 1; i >= 0; i--) {
     BasicBlock* block = schedule_->rpo_order()->at(i);
+    // TODO(titzer): we place at most one floating control structure per
+    // basic block because scheduling currently can interleave phis from
+    // one subgraph with the merges from another subgraph.
+    bool one_placed = false;
     for (int j = static_cast<int>(block->nodes_.size()) - 1; j >= 0; j--) {
       Node* node = block->nodes_[j];
       SchedulerData* data = GetData(node);
-      if (data->is_floating_control_ && !data->is_connected_control_) {
+      if (data->is_floating_control_ && !data->is_connected_control_ &&
+          !one_placed) {
         Trace("  Floating control #%d:%s was scheduled in B%d\n", node->id(),
               node->op()->mnemonic(), block->id());
         ConnectFloatingControlSubgraph(block, node);
+        one_placed = true;
       }
     }
   }
 
   return true;
 }
 
 
 void Scheduler::ConnectFloatingControlSubgraph(BasicBlock* block, Node* end) {
   Node* block_start = block->nodes_[0];
@@ skipping 452 matching lines @@
 
 #if DEBUG
   if (FLAG_trace_turbo_scheduler) PrintRPO(num_loops, loops, final_order);
   VerifySpecialRPO(num_loops, loops, final_order);
 #endif
   return final_order;
 }
 }
 }
 }  // namespace v8::internal::compiler