ARM: Implement memcpy using NEON.

src/platform-posix.cc

Index: src/platform-posix.cc
diff --git a/src/platform-posix.cc b/src/platform-posix.cc
index f76ec4433265df5fc347ec32cdd4a16f864eea4c..5ece279d577a165b5c36a6c2e12e2ba40dabe59f 100644
--- a/src/platform-posix.cc
+++ b/src/platform-posix.cc
@@ -340,7 +340,26 @@ void OS::MemMove(void* dest, const void* src, size_t size) {
   (*memmove_function)(dest, src, size);
 }
 
-#endif  // V8_TARGET_ARCH_IA32
+#elif defined(V8_HOST_ARCH_ARM) && defined(V8_HOST_CAN_READ_UNALIGNED)
+void OS::MemCopyUint16Uint8Wrapper(uint16_t* dest,
+                               const uint8_t* src,
+                               size_t chars) {
+  uint16_t* limit = dest + chars;
+  while (dest < limit) {
+    *dest++ = static_cast<uint16_t>(*src++);
+  }
+}
+
+
+OS::MemCopyUint8Function OS::memcopy_uint8_function = &OS::MemCopyUint8Wrapper;
+OS::MemCopyUint16Uint8Function OS::memcopy_uint16_uint8_function =
+    &OS::MemCopyUint16Uint8Wrapper;
+// Defined in codegen-arm.cc.
+OS::MemCopyUint8Function CreateMemCopyUint8Function(
+    OS::MemCopyUint8Function stub);
+OS::MemCopyUint16Uint8Function CreateMemCopyUint16Uint8Function(
+    OS::MemCopyUint16Uint8Function stub);
+#endif
 
 
 void POSIXPostSetUp() {
@@ -349,6 +368,11 @@ void POSIXPostSetUp() {
   if (generated_memmove != NULL) {
     memmove_function = generated_memmove;
   }
+#elif defined(V8_HOST_ARCH_ARM) && defined(V8_HOST_CAN_READ_UNALIGNED)
+  OS::memcopy_uint8_function =
+      CreateMemCopyUint8Function(&OS::MemCopyUint8Wrapper);
+  OS::memcopy_uint16_uint8_function =
+      CreateMemCopyUint16Uint8Function(&OS::MemCopyUint16Uint8Wrapper);
 #endif
   init_fast_sin_function();
   init_fast_cos_function();