De-templatize Sk4pxXfermode code a bit.

include/core/SkPostConfig.h

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkPostConfig_DEFINED
 #define SkPostConfig_DEFINED
 
@@ skipping 279 matching lines @@
  *     SK_ALWAYS_INLINE void someMethod() { ... }   // should always be inlined
  */
 #if !defined(SK_ALWAYS_INLINE)
 #  if defined(SK_BUILD_FOR_WIN)
 #    define SK_ALWAYS_INLINE __forceinline
 #  else
 #    define SK_ALWAYS_INLINE SK_ATTRIBUTE(always_inline) inline
 #  endif
 #endif
 
+#if defined(SK_BUILD_FOR_WIN)
+    #define SK_VECTORCALL __vectorcall
+#elif defined(SK_CPU_ARM32)
+    #define SK_VECTORCALL __attribute__((pcs("aapcs-vfp")))
+#else
+    #define SK_VECTORCALL
+#endif
+
 //////////////////////////////////////////////////////////////////////
 
 #if defined(__clang__) || defined(__GNUC__)
 #  define SK_PREFETCH(ptr) __builtin_prefetch(ptr)
 #  define SK_WRITE_PREFETCH(ptr) __builtin_prefetch(ptr, 1)
 #else
 #  define SK_PREFETCH(ptr)
 #  define SK_WRITE_PREFETCH(ptr)
 #endif
 
@@ skipping 43 matching lines @@
 #  define SK_GAMMA_EXPONENT (2.2f)
 #endif
 
 //////////////////////////////////////////////////////////////////////
 
 #ifndef GR_TEST_UTILS
 #  define GR_TEST_UTILS 1
 #endif
 
 #endif // SkPostConfig_DEFINED