Cycles: Move non-vectorized bitscan() to util

This way we can use bitscan() from both vectorized and non-vectorized
code, which applies to both kernel and host code.

intern/cycles/bvh/bvh_build.cpp

@@ -34,21 +34,6 @@
 
 CCL_NAMESPACE_BEGIN
 
-#if !defined(__KERNEL_SSE2__)
-/* TODO(sergey): Move to some generic header so all code
- * can use bitscan on non-SSE processors.
- */
-ccl_device_inline int bitscan(int value)
-{
-	assert(value != 0);
-	int bit = 0;
-	while(value >>= 1) {
-		++bit;
-	}
-	return bit;
-}
-#endif
-
 /* BVH Build Task */
 
 class BVHBuildTask : public Task {

intern/cycles/util/util_simd.h

@@ -430,6 +430,23 @@ __forceinline __int64 _mm_extract_epi64( __m128i input, const int index ) {
 
 #endif
 
+#else  /* __KERNEL_SSE2__ */
+
+/* This section is for utility functions which operates on non-register data
+ * which might be used from a non-vectorized code.
+ */
+
+ccl_device_inline int bitscan(int value)
+{
+	assert(value != 0);
+	int bit = 0;
+	while(value >>= 1) {
+		++bit;
+	}
+	return bit;
+}
+
+
 #endif /* __KERNEL_SSE2__ */
 
 CCL_NAMESPACE_END