[turbofan] Reduce memory consumption of graph building

src/compiler/generic-node.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_GENERIC_NODE_H_
 #define V8_COMPILER_GENERIC_NODE_H_
 
 #include "src/v8.h"
 
 #include "src/zone-containers.h"
@@ skipping 74 matching lines @@
    private:
     GenericNode* node_;
   };
 
   Uses uses() { return Uses(this); }
 
   class Edge;
 
   bool OwnedBy(GenericNode* owner) const;
 
-  static S* New(GenericGraphBase* graph, int input_count, S** inputs);
+  static S* New(GenericGraphBase* graph, int input_count, S** inputs,
+                bool has_extensible_inputs);
 
  protected:
   friend class GenericGraphBase;
 
   class Use : public ZoneObject {
    public:
     GenericNode* from;
     Use* next;
     Use* prev;
     int input_index;
@@ skipping 15 matching lines @@
     } else {
       return inputs_.static_ + index;
     }
   }
 
   inline void AppendUse(Use* use);
   inline void RemoveUse(Use* use);
 
   void* operator new(size_t, void* location) { return location; }
 
-  GenericNode(GenericGraphBase* graph, int input_count);
+  GenericNode(GenericGraphBase* graph, int input_count,
+              int reserved_input_count);
 
  private:
   void AssignUniqueID(GenericGraphBase* graph);
 
   typedef ZoneDeque<Input> InputDeque;
 
+  static const int kReservedInputCountBits = 2;
+  static const int kMaxReservedInputs = (1 << kReservedInputCountBits) - 1;
+  static const int kDefaultReservedInputs = kMaxReservedInputs;
+
   NodeId id_;
-  int input_count_ : 31;
+  int input_count_ : 29;
+  unsigned int reserve_input_count_ : kReservedInputCountBits;
   bool has_appendable_inputs_ : 1;
   union {
     // When a node is initially allocated, it uses a static buffer to hold its
     // inputs under the assumption that the number of outputs will not increase.
     // When the first input is appended, the static buffer is converted into a
     // deque to allow for space-efficient growing.
     Input* static_;
     InputDeque* appendable_;
   } inputs_;
   int use_count_;
@@ skipping 113 matching lines @@
   }
 
   typename GenericNode<B, S>::Use* current_;
   int index_;
 };
 }
 }
 }  // namespace v8::internal::compiler
 
 #endif  // V8_COMPILER_GENERIC_NODE_H_