Eliminate temporary locals for some expressions

runtime/vm/bit_vector.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_BIT_VECTOR_H_
 #define VM_BIT_VECTOR_H_
 
 #include "vm/allocation.h"
 #include "vm/isolate.h"
 #include "vm/zone.h"
@@ skipping 30 matching lines @@
     intptr_t word_index_;
     uword current_word_;
 
     friend class BitVector;
   };
 
   explicit BitVector(intptr_t length)
       : length_(length),
         data_length_(SizeFor(length)),
         data_(Isolate::Current()->current_zone()->Alloc<uword>(data_length_)) {
-    ASSERT(length > 0);
     Clear();
   }
 
   void CopyFrom(const BitVector* other) {
     Clear();
     AddAll(other);
   }
 
   static intptr_t SizeFor(intptr_t length) {
     return 1 + ((length - 1) / kBitsPerWord);
@@ skipping 49 matching lines @@
   intptr_t length_;
   intptr_t data_length_;
   uword* data_;
 
   DISALLOW_COPY_AND_ASSIGN(BitVector);
 };
 
 }  // namespace dart
 
 #endif  // VM_BIT_VECTOR_H_