use intrinsics on more platforms for SkCLZ

include/core/SkMath.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 SkMath_DEFINED
@@ skipping 22 matching lines @@
 
 /** Return the integer square root of n, treated as a SkFixed (16.16)
  */
 #define SkSqrt32(n)         SkSqrtBits(n, 15)
 
 ///////////////////////////////////////////////////////////////////////////////
 
 //! Returns the number of leading zero bits (0...32)
 int SkCLZ_portable(uint32_t);
 
-#if defined(SK_CPU_ARM)
-    #define SkCLZ(x)    __builtin_clz(x)
-#endif
+#ifndef SkCLZ
+    #if defined(_MSC_VER) && _MSC_VER >= 1400
+        #include <intrin.h>
 
-#ifndef SkCLZ
-    #define SkCLZ(x)    SkCLZ_portable(x)
+        static inline int SkCLZ(uint32_t mask) {
+            if (mask) {
+                DWORD index;
+                _BitScanReverse(&index, mask);
+                return index ^ 0x1F;
+            } else {
+                return 32;
+            }
+        }
+    #elif defined(SK_CPU_ARM) || defined(__GNUC__)
+        #define SkCLZ(x)    __builtin_clz(x)
+    #else
+        #define SkCLZ(x)    SkCLZ_portable(x)
+    #endif
 #endif
 
 /**
  *  Returns (value < 0 ? 0 : value) efficiently (i.e. no compares or branches)
  */
 static inline int SkClampPos(int value) {
     return value & ~(value >> 31);
 }
 
 /** Given an integer and a positive (max) integer, return the value
@@ skipping 93 matching lines @@
  *  Only valid if a and b are unsigned and <= 32767.
  */
 static inline U8CPU SkMulDiv255Round(U16CPU a, U16CPU b) {
     SkASSERT(a <= 32767);
     SkASSERT(b <= 32767);
     unsigned prod = SkMulS16(a, b) + 128;
     return (prod + (prod >> 8)) >> 8;
 }
 
 #endif