Reland "Remove V8_HOST_CAN_READ_UNALIGNED and its uses."

src/utils.h

Index: src/utils.h
diff --git a/src/utils.h b/src/utils.h
index 07b6490bf363dd4727763eb58dcc26c989dee48b..c23cf05f6fa96642d9ee124c03202eb0556dac2b 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -680,20 +680,11 @@ inline int CompareCharsUnsigned(const lchar* lhs,
                                 const rchar* rhs,
                                 int chars) {
   const lchar* limit = lhs + chars;
-#ifdef V8_HOST_CAN_READ_UNALIGNED
-  if (sizeof(*lhs) == sizeof(*rhs)) {
-    // Number of characters in a uintptr_t.
-    static const int kStepSize = sizeof(uintptr_t) / sizeof(*lhs);  // NOLINT
-    while (lhs <= limit - kStepSize) {
-      if (*reinterpret_cast<const uintptr_t*>(lhs) !=
-          *reinterpret_cast<const uintptr_t*>(rhs)) {
-        break;
-      }
-      lhs += kStepSize;
-      rhs += kStepSize;
-    }
+  if (sizeof(*lhs) == sizeof(char) && sizeof(*rhs) == sizeof(char)) {
+    // memcmp compares byte-by-byte, yielding wrong results for two-byte
+    // strings on little-endian systems.
+    return memcmp(lhs, rhs, chars);
   }
-#endif
   while (lhs < limit) {
     int r = static_cast<int>(*lhs) - static_cast<int>(*rhs);
     if (r != 0) return r;
@@ -1286,15 +1277,11 @@ void CopyChars(sinkchar* dest, const sourcechar* src, int 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)) &&
       (chars >= static_cast<int>(kMinComplexMemCopy / sizeof(*dest)))) {
     MemCopy(dest, src, chars * sizeof(*dest));
-    return;
-  }
-#endif
-  while (dest < limit) {
-    *dest++ = static_cast<sinkchar>(*src++);
+  } else {
+    while (dest < limit) *dest++ = static_cast<sinkchar>(*src++);
   }
 }