Implement control reducer, which reduces branches and phis together in a single fixpoint.

src/compiler/operator-properties-inl.h

 // 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.
 
 #ifndef V8_COMPILER_OPERATOR_PROPERTIES_INL_H_
 #define V8_COMPILER_OPERATOR_PROPERTIES_INL_H_
 
 #include "src/compiler/common-operator.h"
 #include "src/compiler/js-operator.h"
 #include "src/compiler/linkage.h"
@@ skipping 96 matching lines @@
       op->opcode() == IrOpcode::kFinish ||
       op->opcode() == IrOpcode::kTerminate) {
     return OpParameter<int>(op);
   }
   if (op->HasProperty(Operator::kNoRead) && op->HasProperty(Operator::kNoWrite))
     return 0;  // no effects.
   return 1;
 }
 
 inline int OperatorProperties::GetControlInputCount(const Operator* op) {
+  // TODO(titzer): fix this mess; just make them a count on the operator.
   switch (op->opcode()) {
     case IrOpcode::kPhi:
     case IrOpcode::kEffectPhi:
     case IrOpcode::kLoad:
     case IrOpcode::kLoadElement:
     case IrOpcode::kLoadField:
       return 1;
 #define OPCODE_CASE(x) case IrOpcode::k##x:
       CONTROL_OP_LIST(OPCODE_CASE)
 #undef OPCODE_CASE
-      // Branch operator is special
       if (op->opcode() == IrOpcode::kBranch) return 1;
+      if (op->opcode() == IrOpcode::kTerminate) return 1;
       // Control operators are Operator1<int>.
       return OpParameter<int>(op);
     default:
       // Operators that have write effects must have a control
       // dependency. Effect dependencies only ensure the correct order of
       // write/read operations without consideration of control flow. Without an
       // explicit control dependency writes can be float in the schedule too
       // early along a path that shouldn't generate a side-effect.
       return op->HasProperty(Operator::kNoWrite) ? 0 : 1;
   }
@@ skipping 46 matching lines @@
          opcode == IrOpcode::kDead || opcode == IrOpcode::kLoop ||
          opcode == IrOpcode::kMerge || opcode == IrOpcode::kIfTrue ||
          opcode == IrOpcode::kIfFalse;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_OPERATOR_PROPERTIES_INL_H_