Backout e54c650e8748 (bug 737239) due to lack of proper reviews.

gfx/thebes/gfxUtils.h

@@ -181,14 +181,48 @@ public:
 namespace mozilla {
 namespace gfx {
 
-
 /*
- * Copyright 2008 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.
+ * Copyright 2008 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.
  */
 
+// Some helper functions for power-of-two arithmetic
+// from Skia
+#if defined(__arm__)
+    #define CountLeadingZeroes(x) __builtin_clz(x)
+#else
+
+#define sub_shift(zeros, x, n)  \
+    zeros -= n;                 \
+    x >>= n
+
+static inline int CountLeadingZeroes(uint32_t aNumber)
+{
+    if (aNumber == 0) {
+        return 32;
+    }
+    int zeros = 31;
+    if (aNumber & 0xFFFF0000) {
+        sub_shift(zeros, aNumber, 16);
+    }
+    if (aNumber & 0xFF00) {
+        sub_shift(zeros, aNumber, 8);
+    }
+    if (aNumber & 0xF0) {
+        sub_shift(zeros, aNumber, 4);
+    }
+    if (aNumber & 0xC) {
+        sub_shift(zeros, aNumber, 2);
+    }
+    if (aNumber & 0x2) {
+        sub_shift(zeros, aNumber, 1);
+    }
+    return zeros;
+}
+#endif
+
 /**
  * Returns true if |aNumber| is a power of two
  */
@@ -205,17 +239,7 @@ IsPowerOfTwo(int aNumber)
 static inline int
 NextPowerOfTwo(int aNumber)
 {
-#if defined(__arm__)
-    return 1 << (32 - __builtin_clz(aNumber - 1));
-#else
-    --aNumber;
-    aNumber |= aNumber >> 1;
-    aNumber |= aNumber >> 2;
-    aNumber |= aNumber >> 4;
-    aNumber |= aNumber >> 8;
-    aNumber |= aNumber >> 16;
-    return ++aNumber;
-#endif
+    return 1 << (32 - CountLeadingZeroes(aNumber - 1));
 }
 
 } // namespace gfx