Do not use wide reads in CopyCharsUnsigned.

src/utils.h

 // Copyright 2012 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_UTILS_H_
 #define V8_UTILS_H_
 
 #include <limits.h>
 #include <stdlib.h>
 #include <string.h>
@@ skipping 1269 matching lines @@
                         reinterpret_cast<const uint16_t*>(src),
                         chars);
     }
   }
 }
 
 template <typename sourcechar, typename sinkchar>
 void CopyCharsUnsigned(sinkchar* dest, const sourcechar* src, int chars) {
   sinkchar* limit = dest + chars;
 #ifdef V8_HOST_CAN_READ_UNALIGNED
-  if (sizeof(*dest) == sizeof(*src)) {
-    if (chars >= static_cast<int>(kMinComplexMemCopy / sizeof(*dest))) {
-      MemCopy(dest, src, chars * sizeof(*dest));
-      return;
-    }
-    // Number of characters in a uintptr_t.
-    static const int kStepSize = sizeof(uintptr_t) / sizeof(*dest);  // NOLINT
-    DCHECK(dest + kStepSize > dest);  // Check for overflow.
-    while (dest + kStepSize <= limit) {
-      *reinterpret_cast<uintptr_t*>(dest) =
-          *reinterpret_cast<const uintptr_t*>(src);
-      dest += kStepSize;
-      src += kStepSize;
-    }
+  if ((sizeof(*dest) == sizeof(*src)) &&
+      (chars >= static_cast<int>(kMinComplexMemCopy / sizeof(*dest)))) {
+    MemCopy(dest, src, chars * sizeof(*dest));
+    return;
   }
 #endif
   while (dest < limit) {
     *dest++ = static_cast<sinkchar>(*src++);
   }
 }
 
 
 #if defined(V8_HOST_ARCH_ARM)
 void CopyCharsUnsigned(uint8_t* dest, const uint8_t* src, int chars) {
@@ skipping 163 matching lines @@
   // Takes the address of the limit variable in order to find out where
   // the top of stack is right now.
   uintptr_t limit = reinterpret_cast<uintptr_t>(&limit);
   return limit;
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_UTILS_H_