Allocate the environment's location backing store during register allocation.

runtime/vm/intermediate_language.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.
 
 #ifndef VM_INTERMEDIATE_LANGUAGE_H_
 #define VM_INTERMEDIATE_LANGUAGE_H_
 
 #include "vm/allocation.h"
 #include "vm/ast.h"
 #include "vm/growable_array.h"
@@ skipping 2660 matching lines @@
   DISALLOW_COPY_AND_ASSIGN(BranchInstr);
 };
 
 
 #undef DECLARE_INSTRUCTION
 
 
 class Environment : public ZoneAllocated {
  public:
   // Construct an environment by copying from an array of values.
-  // TODO(vegorov): it's absolutely crucial that locations_ backing store
-  // is preallocated and never reallocated.  We use pointers into it
-  // during register allocation.
   explicit Environment(const GrowableArray<Value*>& values,
                        intptr_t fixed_parameter_count)
       : values_(values.length()),
-        locations_(values.length()),
+        locations_(NULL),
         fixed_parameter_count_(fixed_parameter_count) {
     values_.AddArray(values);
   }
 
   const GrowableArray<Value*>& values() const {
     return values_;
   }
 
-  void AddLocation(Location value) {
-    locations_.Add(value);
+  void InitializeLocations() {
+    locations_ =
+        Isolate::Current()->current_zone()->Alloc<Location>(values_.length());
   }
 
   Location LocationAt(intptr_t ix) const {
     return locations_[ix];

[Kevin Millikin (Google), 2012/08/06 14:59:18]

It's not bulletproof, but I think I'll assert ix is in the (current) range of 0
<= ix < values_.length().  Also just below.

   }
 
   Location* LocationSlotAt(intptr_t ix) const {
-    return & locations_[ix];
+    return &locations_[ix];
   }
 
   intptr_t fixed_parameter_count() const {
     return fixed_parameter_count_;
   }
 
   void PrintTo(BufferFormatter* f) const;
 
  private:
   GrowableArray<Value*> values_;
-  GrowableArray<Location> locations_;
+  Location* locations_;
   const intptr_t fixed_parameter_count_;
 
   DISALLOW_COPY_AND_ASSIGN(Environment);
 };
 
 
 // Visitor base class to visit each instruction and computation in a flow
 // graph as defined by a reversed list of basic blocks.
 class FlowGraphVisitor : public ValueObject {
  public:
@@ skipping 23 matching lines @@
   const GrowableArray<BlockEntryInstr*>& block_order_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(FlowGraphVisitor);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_INTERMEDIATE_LANGUAGE_H_