ARM: Implement memcpy using NEON.

src/platform.h

Index: src/platform.h
diff --git a/src/platform.h b/src/platform.h
index 24d21cb3aee129ba84df74a0b8b1037312b24a15..211be39d00c781b7075250d0e149e2b8dcc676e0 100644
--- a/src/platform.h
+++ b/src/platform.h
@@ -315,6 +315,9 @@ class OS {
   // Support runtime detection of Cpu implementer
   static CpuImplementer GetCpuImplementer();
 
+  // Support runtime detection of Cpu implementer
+  static CpuPart GetCpuPart(CpuImplementer implementer);
+
   // Support runtime detection of VFP3 on ARM CPUs.
   static bool ArmCpuHasFeature(CpuFeature feature);
 
@@ -343,7 +346,42 @@ class OS {
   static void MemCopy(void* dest, const void* src, size_t size) {
     MemMove(dest, src, size);
   }
-#else  // V8_TARGET_ARCH_IA32
+#elif defined(V8_HOST_ARCH_ARM)
+  typedef void (*MemCopyUint8Function)(uint8_t* dest,
+                                       const uint8_t* src,
+                                       size_t size);
+  static MemCopyUint8Function memcopy_uint8_function;
+  static void MemCopyUint8Wrapper(uint8_t* dest,
+                                  const uint8_t* src,
+                                  size_t chars) {
+    memcpy(dest, src, chars);
+  }
+  // For values < 16, the assembler function is slower than the inlined C code.
+  static const int kMinComplexMemCopy = 16;
+  static void MemCopy(void* dest, const void* src, size_t size) {
+    (*memcopy_uint8_function)(reinterpret_cast<uint8_t*>(dest),
+                              reinterpret_cast<const uint8_t*>(src),
+                              size);
+  }
+  static void MemMove(void* dest, const void* src, size_t size) {
+    memmove(dest, src, size);
+  }
+
+  typedef void (*MemCopyUint16Uint8Function)(uint16_t* dest,
+                                             const uint8_t* src,
+                                             size_t size);
+  static MemCopyUint16Uint8Function memcopy_uint16_uint8_function;
+  static void MemCopyUint16Uint8Wrapper(uint16_t* dest,
+                                        const uint8_t* src,
+                                        size_t chars);
+  // For values < 12, the assembler function is slower than the inlined C code.
+  static const int kMinComplexConvertMemCopy = 12;
+  static void MemCopyUint16Uint8(uint16_t* dest,
+                                 const uint8_t* src,
+                                 size_t size) {
+    (*memcopy_uint16_uint8_function)(dest, src, size);
+  }
+#else
   // Copy memory area to disjoint memory area.
   static void MemCopy(void* dest, const void* src, size_t size) {
     memcpy(dest, src, size);