Fix test timeout; faster DEBUG String::CharAt by not using mutable accessor.

runtime/vm/object.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_OBJECT_H_
 #define VM_OBJECT_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/utils.h"
@@ skipping 5823 matching lines @@
   friend class ExternalOneByteString;
   friend class ExternalTwoByteString;
   // So that the MarkingVisitor can print a debug string from a NoHandleScope.
   friend class MarkingVisitor;
 };
 
 
 class OneByteString : public AllStatic {
  public:
   static uint16_t CharAt(const String& str, intptr_t index) {
-    NoGCScope no_gc;
-    return *CharAddr(str, index);
+    ASSERT((index >= 0) && (index < str.Length()));
+    ASSERT(str.IsOneByteString());
+    return raw_ptr(str)->data()[index];
   }
 
   static void SetCharAt(const String& str, intptr_t index, uint8_t code_unit) {
     NoGCScope no_gc;
     *CharAddr(str, index) = code_unit;
   }
   static RawOneByteString* EscapeSpecialCharacters(const String& str);
   // We use the same maximum elements for all strings.
   static const intptr_t kBytesPerElement = 1;
   static const intptr_t kMaxElements = String::kMaxElements;
@@ skipping 109 matching lines @@
   friend class ExternalOneByteString;
   friend class SnapshotReader;
   friend class StringHasher;
 };
 
 
 class TwoByteString : public AllStatic {
  public:
   static uint16_t CharAt(const String& str, intptr_t index) {
     NoGCScope no_gc;
     return *CharAddr(str, index);

[Ivan Posva, 2014/10/20 21:15:10]

How about fixing it here as well?

[koda, 2014/10/20 23:58:28]

Done.

   }
 
   static void SetCharAt(const String& str, intptr_t index, uint16_t ch) {
     NoGCScope no_gc;
     *CharAddr(str, index) = ch;
   }
 
   static RawTwoByteString* EscapeSpecialCharacters(const String& str);
 
   // We use the same maximum elements for all strings.
@@ skipping 80 matching lines @@
   friend class Class;
   friend class String;
   friend class SnapshotReader;
 };
 
 
 class ExternalOneByteString : public AllStatic {
  public:
   static uint16_t CharAt(const String& str, intptr_t index) {
     NoGCScope no_gc;
     return *CharAddr(str, index);

[Ivan Posva, 2014/10/20 21:15:10]

Ditto, here and other places.

[koda, 2014/10/20 23:58:28]

Not needed for external strings, since their CharAddr returns a const pointer,
and hence do not incur the overhead.

   }
 
   static void* GetPeer(const String& str) {
     return raw_ptr(str)->external_data_->peer();
   }
 
   // We use the same maximum elements for all strings.
   static const intptr_t kBytesPerElement = 1;
   static const intptr_t kMaxElements = String::kMaxElements;
 
@@ skipping 1470 matching lines @@
 
 
 RawObject* MegamorphicCache::GetTargetFunction(const Array& array,
                                                intptr_t index) {
   return array.At((index * kEntryLength) + kTargetFunctionIndex);
 }
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_