New linear scan allocator.

runtime/vm/growable_array.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 // Defines growable array classes, that differ where they are allocated:
 // - GrowableArray: allocate on stack.
 // - ZoneGrowableArray: allocated in the zone.
 
 #ifndef VM_GROWABLE_ARRAY_H_
 #define VM_GROWABLE_ARRAY_H_
 
@@ skipping 18 matching lines @@
     if (initial_capacity > 0) {
       capacity_ = Utils::RoundUpToPowerOfTwo(initial_capacity);
       data_ = reinterpret_cast<T*>(zone_->Allocate(capacity_ * sizeof(T)));
     }
   }
 
   int length() const { return length_; }
   T* data() const { return data_; }
   bool is_empty() const { return length_ == 0; }
 
+  void TruncateTo(intptr_t length) {
+    ASSERT(length_ >= length);
+    length_ = length;
+  }
+
   void Add(const T& value) {
     Resize(length() + 1);
     Last() = value;
   }
 
   void RemoveLast() {
     ASSERT(length_ > 0);
     length_--;
   }
 
@@ skipping 95 matching lines @@
           initial_capacity,
           Isolate::Current()->current_zone()->GetBaseZone()) {}
   ZoneGrowableArray() :
       BaseGrowableArray<T, ZoneAllocated>(
           Isolate::Current()->current_zone()->GetBaseZone()) {}
 };
 
 }  // namespace dart
 
 #endif  // VM_GROWABLE_ARRAY_H_