[turbofan] Reduce memory consumption of graph building

src/compiler/generic-node-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_GENERIC_NODE_INL_H_
 #define V8_COMPILER_GENERIC_NODE_INL_H_
 
 #include "src/v8.h"
 
 #include "src/compiler/generic-graph.h"
 #include "src/compiler/generic-node.h"
 #include "src/zone.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
 template <class B, class S>
-GenericNode<B, S>::GenericNode(GenericGraphBase* graph, int input_count)
+GenericNode<B, S>::GenericNode(GenericGraphBase* graph, int input_count,
+                               int reserve_input_count)
     : BaseClass(graph->zone()),
       input_count_(input_count),
+      reserve_input_count_(reserve_input_count),
       has_appendable_inputs_(false),
       use_count_(0),
       first_use_(NULL),
       last_use_(NULL) {
+  DCHECK(reserve_input_count <= kMaxReservedInputs);
   inputs_.static_ = reinterpret_cast<Input*>(this + 1);
   AssignUniqueID(graph);
 }
 
 template <class B, class S>
 inline void GenericNode<B, S>::AssignUniqueID(GenericGraphBase* graph) {
   id_ = graph->NextNodeID();
 }
 
 template <class B, class S>
@@ skipping 111 matching lines @@
     for (int i = 0; i < input_count_; ++i) {
       deque->push_back(inputs_.static_[i]);
     }
     inputs_.appendable_ = deque;
     has_appendable_inputs_ = true;
   }
 }
 
 template <class B, class S>
 void GenericNode<B, S>::AppendInput(Zone* zone, GenericNode<B, S>* to_append) {
-  EnsureAppendableInputs(zone);
   Use* new_use = new (zone) Use;
   Input new_input;
   new_input.to = to_append;
   new_input.use = new_use;
-  inputs_.appendable_->push_back(new_input);
+  if (reserve_input_count_ > 0) {
+    DCHECK(!has_appendable_inputs_);
+    reserve_input_count_--;
+    inputs_.static_[input_count_] = new_input;
+  } else {
+    EnsureAppendableInputs(zone);
+    inputs_.appendable_->push_back(new_input);
+  }
   new_use->input_index = input_count_;
   new_use->from = this;
   to_append->AppendUse(new_use);
   input_count_++;
 }
 
 template <class B, class S>
 void GenericNode<B, S>::InsertInput(Zone* zone, int index,
                                     GenericNode<B, S>* to_insert) {
   DCHECK(index >= 0 && index < InputCount());
@@ skipping 44 matching lines @@
   --use_count_;
 }
 
 template <class B, class S>
 inline bool GenericNode<B, S>::OwnedBy(GenericNode* owner) const {
   return first_use_ != NULL && first_use_->from == owner &&
          first_use_->next == NULL;
 }
 
 template <class B, class S>
-S* GenericNode<B, S>::New(GenericGraphBase* graph, int input_count,
-                          S** inputs) {
+S* GenericNode<B, S>::New(GenericGraphBase* graph, int input_count, S** inputs,
+                          bool has_extensible_inputs) {
   size_t node_size = sizeof(GenericNode);
-  size_t inputs_size = input_count * sizeof(Input);
+  size_t reserve_input_count =
+      has_extensible_inputs ? kDefaultReservedInputs : 0;
+  size_t inputs_size = (input_count + reserve_input_count) * sizeof(Input);
   size_t uses_size = input_count * sizeof(Use);
   int size = static_cast<int>(node_size + inputs_size + uses_size);
   Zone* zone = graph->zone();
   void* buffer = zone->New(size);
-  S* result = new (buffer) S(graph, input_count);
+  S* result = new (buffer) S(graph, input_count, reserve_input_count);
   Input* input =
       reinterpret_cast<Input*>(reinterpret_cast<char*>(buffer) + node_size);
   Use* use =
       reinterpret_cast<Use*>(reinterpret_cast<char*>(input) + inputs_size);
 
   for (int current = 0; current < input_count; ++current) {
     GenericNode* to = *inputs++;
     input->to = to;
     input->use = use;
     use->input_index = current;
     use->from = result;
     to->AppendUse(use);
     ++use;
     ++input;
   }
   return result;
 }
 }
 }
 }  // namespace v8::internal::compiler
 
 #endif  // V8_COMPILER_GENERIC_NODE_INL_H_