[WIP] Supporting arm_neon_optional flag for blink platform.

Source/wtf/CPU.h

Index: Source/wtf/CPU.h
diff --git a/Source/wtf/CPU.h b/Source/wtf/CPU.h
index 061d128afab82d7c4883c04f7e28a4d226e0e4a8..ada4d8521b5a1bfc3f44b644a086e17229978f60 100644
--- a/Source/wtf/CPU.h
+++ b/Source/wtf/CPU.h
@@ -2,7 +2,7 @@
  * Copyright (C) 2006, 2007, 2008, 2009, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2007-2009 Torch Mobile, Inc.
  * Copyright (C) 2010, 2011 Research In Motion Limited. All rights reserved.
- * Copyright (C) 2013 Samsung Electronics. All rights reserved.
+ * Copyright (C) 2013-2014 Samsung Electronics. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -155,12 +155,39 @@
 #  endif
 #endif /* !defined(WTF_CPU_ARM_THUMB2) */
 
-#if defined(__ARM_NEON__) && !defined(WTF_CPU_ARM_NEON)
-#define WTF_CPU_ARM_NEON 1
+// The isSupportedNEON() function returns true if the target device
+// is ARMv7-A and supports Neon instructions. In OPTIONAL mode, this actually
+// probes the CPU at runtime (and caches the result).
+#if CPU(ARM_NEON)
+static inline bool isSupportedNEON(void) { return true; }
+#elif CPU(ARM_NEON_OPTIONAL)
+extern bool isSupportedNEON(void) WTF_PURE_FUNCTION;
+#else
+static inline bool isSupportedNEON(void) { return false; }
+#endif
+
+// Helper macro
+#if CPU(ARM)
+#define WTF_CPU_ARM_HAS_NEON() isSupportedNEON()
+#endif
+
+// Use WTF_CPU_ARM_NEON_WRAP(symbol) to map 'symbol' to a NEON-specific symbol
+// when applicable. This will transform 'symbol' differently depending on
+// the current NEON configuration, i.e.:
+//
+//    NONE                             -> 'symbol'
+//    WTF_CPU_ARM_NEON                 -> 'symbolNEON'
+//    WTF_CPU_ARM_NEON_OPTIONAL        -> 'symbol' or 'symbolNEON' depending on runtime check.
+#if CPU(ARM_NEON)
+#  define WTF_CPU_ARM_NEON_WRAP(x) (x ## NEON)
+#elif CPU(ARM_NEON_OPTIONAL)
+#  define WTF_CPU_ARM_NEON_WRAP(x) (WTF_CPU_ARM_HAS_NEON() ? x ## NEON : x)
+#else
+#  define WTF_CPU_ARM_NEON_WRAP(x) (x)
 #endif
 
-#if CPU(ARM_NEON) && (!COMPILER(GCC) || GCC_VERSION_AT_LEAST(4, 7, 0))
-// All NEON intrinsics usage can be disabled by this macro.
+#if (CPU(ARM_NEON) || CPU(ARM_NEON_OPTIONAL)) && (!COMPILER(GCC) || GCC_VERSION_AT_LEAST(4, 7, 0))
+// All NEON intrinsics usage can be enabled by this macro.
 #define HAVE_ARM_NEON_INTRINSICS 1
 #endif