The function CopyCharsUnsigned(uint8_t* dest, const uint8_t* src, size_t chars) is now a specializa…

src/utils.h

Index: src/utils.h
diff --git a/src/utils.h b/src/utils.h
index 8eca39207d4aa55b222870a2e36e7ce53a273bc8..8111076f606715e776fe01d73efb373e9185e489 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -441,6 +441,18 @@ typedef void (*MemMoveFunction)(void* dest, const void* src, size_t size);
 V8_INLINE void MemCopy(void* dest, const void* src, size_t size) {
   MemMove(dest, src, size);
 }
+#elif defined(V8_TARGET_ARCH_X64)
+// Limit below which the extra overhead of the MemCopy function is likely
+// to outweigh the benefits of faster copying.
+const int kMinComplexMemCopy = 8;
+
+// Copy memory area to disjoint memory area.
+V8_INLINE void MemCopy(void* dest, const void* src, size_t size) {
+  memcpy(dest, src, size);
+}
+V8_INLINE void MemMove(void* dest, const void* src, size_t size) {
+  memmove(dest, src, size);
+}
 #elif defined(V8_HOST_ARCH_ARM)
 typedef void (*MemCopyUint8Function)(uint8_t* dest, const uint8_t* src,
                                      size_t size);
@@ -1154,7 +1166,9 @@ Vector<const char> ReadFile(FILE* file,
 template <typename sourcechar, typename sinkchar>
 INLINE(static void CopyCharsUnsigned(sinkchar* dest, const sourcechar* src,
                                      size_t chars));
-#if defined(V8_HOST_ARCH_ARM)
+#if defined(V8_HOST_ARCH_X64)
+INLINE(void CopyCharsUnsigned(uint8_t* dest, const uint8_t* src, size_t chars));
+#elif defined(V8_HOST_ARCH_ARM)
 INLINE(void CopyCharsUnsigned(uint8_t* dest, const uint8_t* src, size_t chars));
 INLINE(void CopyCharsUnsigned(uint16_t* dest, const uint8_t* src,
                               size_t chars));
@@ -1213,7 +1227,16 @@ void CopyCharsUnsigned(sinkchar* dest, const sourcechar* src, size_t chars) {
 }
 
 
-#if defined(V8_HOST_ARCH_ARM)
+#if defined(V8_HOST_ARCH_X64)
+void CopyCharsUnsigned(uint8_t* dest, const uint8_t* src, size_t chars) {
+  uint8_t* limit = dest + chars;
+  if (chars >= static_cast<int>(kMinComplexMemCopy / sizeof(*dest))) {
+    MemCopy(dest, src, chars * sizeof(*dest));
+  } else {
+    while (dest < limit) *dest++ = *src++;
+  }
+}
+#elif defined(V8_HOST_ARCH_ARM)
 void CopyCharsUnsigned(uint8_t* dest, const uint8_t* src, size_t chars) {
   switch (static_cast<unsigned>(chars)) {
     case 0: