[turbofan] Optimize certain chains of Branch into a Switch.

src/compiler/operator.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_H_
 #define V8_COMPILER_OPERATOR_H_
 
 #include <ostream>  // NOLINT(readability/streams)
 
 #include "src/base/flags.h"
@@ skipping 67 matching lines @@
   // should have unequal hashcodes with high probability.
   virtual size_t HashCode() const { return base::hash<Opcode>()(opcode()); }
 
   // Check whether this operator has the given property.
   bool HasProperty(Property property) const {
     return (properties() & property) == property;
   }
 
   Properties properties() const { return properties_; }
 
+  // TODO(bmeurer): Use bit fields below?
+  static const size_t kMaxControlOutputCount = (1u << 16) - 1;
+
   // TODO(titzer): convert return values here to size_t.
   int ValueInputCount() const { return value_in_; }
   int EffectInputCount() const { return effect_in_; }
   int ControlInputCount() const { return control_in_; }
 
   int ValueOutputCount() const { return value_out_; }
   int EffectOutputCount() const { return effect_out_; }
   int ControlOutputCount() const { return control_out_; }
 
   static size_t ZeroIfPure(Properties properties) {
     return (properties & kPure) == kPure ? 0 : 1;
   }
 
   // TODO(titzer): API for input and output types, for typechecking graph.
  protected:
   // Print the full operator into the given stream, including any
   // static parameters. Useful for debugging and visualizing the IR.
   virtual void PrintTo(std::ostream& os) const;
   friend std::ostream& operator<<(std::ostream& os, const Operator& op);
 
  private:
   Opcode opcode_;
   Properties properties_;
   const char* mnemonic_;
   uint32_t value_in_;
   uint16_t effect_in_;
   uint16_t control_in_;
   uint16_t value_out_;
   uint8_t effect_out_;
-  uint8_t control_out_;
+  uint16_t control_out_;
 
   DISALLOW_COPY_AND_ASSIGN(Operator);
 };
 
 DEFINE_OPERATORS_FOR_FLAGS(Operator::Properties)
 
 std::ostream& operator<<(std::ostream& os, const Operator& op);
 
 
 // A templatized implementation of Operator that has one static parameter of
@@ skipping 59 matching lines @@
   return reinterpret_cast<const Operator1<double, base::bit_equal_to<double>,
                                           base::bit_hash<double>>*>(op)
       ->parameter();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_OPERATOR_H_