diff --git a/moo/lib/bigint.c b/moo/lib/bigint.c
index 9cc5d04..4468afb 100644
--- a/moo/lib/bigint.c
+++ b/moo/lib/bigint.c
@@ -2107,7 +2107,7 @@ moo_oop_t moo_divints (moo_t* moo, moo_oop_t x, moo_oop_t y, int modulo, moo_oop
 					{
  						/* 
 						2**x = v
-						x = logv(2) = log(v) / log(2)
+						x = log2(v)
 						x is the number of shift to make */
 	TODO:
 	DO SHIFTING. how to get remainder..
@@ -2117,7 +2117,7 @@ moo_oop_t moo_divints (moo_t* moo, moo_oop_t x, moo_oop_t y, int modulo, moo_oop
 						if (!z) return MOO_NULL;
 						rshift_unsigned_array (z, MOO_OBJ_GET_SIZE(z), log(v)/log(2));
 					}
-#ebduf
+#endif
 			}
 
 			moo_pushvolat (moo, &x);
diff --git a/moo/lib/moo-utl.h b/moo/lib/moo-utl.h
index 83c6b7c..5b3b4cf 100644
--- a/moo/lib/moo-utl.h
+++ b/moo/lib/moo-utl.h
@@ -640,6 +640,12 @@ MOO_EXPORT moo_oow_t moo_utf16_to_uc (
 
 /* ------------------------------------------------------------------------- */
 
+MOO_EXPORT int moo_log2_for_pow2 (
+	moo_oow_t pow2v
+);
+
+/* ------------------------------------------------------------------------- */
+
 #if defined(MOO_HAVE_UINT16_T)
 MOO_EXPORT moo_uint16_t moo_ntoh16 (
 	moo_uint16_t x
diff --git a/moo/lib/pf-sys.c b/moo/lib/pf-sys.c
index a09eacd..78fb792 100644
--- a/moo/lib/pf-sys.c
+++ b/moo/lib/pf-sys.c
@@ -184,13 +184,13 @@ static MOO_INLINE moo_oop_t _fetch_raw_int (moo_t* moo, moo_int8_t* rawptr, moo_
 			v = ((struct st_int32_t*)&rawptr[offset])->v;
 			break;
 
-	#if defined(MOO_HAVE_INT64_T) &&  (MOO_SIZEOF_OOW_T >= MOO_SIZEOF_INT64_T)
+	#if defined(MOO_HAVE_INT64_T) &&  (MOO_SIZEOF_OOW_T >= 8)
 		case 8: 
 			v = ((struct st_int64_t*)&rawptr[offset])->v;
 			break;
 	#endif
 
-	#if defined(MOO_HAVE_INT128_T) && (MOO_SIZEOF_OOW_T >= MOO_SIZEOF_INT128_T)
+	#if defined(MOO_HAVE_INT128_T) && (MOO_SIZEOF_OOW_T >= 16)
 		case 16: 
 			v = ((struct st_int128_t*)&rawptr[offset])->v;
 			break;
@@ -279,13 +279,13 @@ static MOO_INLINE int _store_raw_int (moo_t* moo, moo_uint8_t* rawptr, moo_oow_t
 			((struct st_int32_t*)&rawptr[offset])->v = w;
 			return 0;
 
-	#if defined(MOO_HAVE_INT64_T) && (MOO_SIZEOF_OOW_T >= MOO_SIZEOF_INT64_T)
+	#if defined(MOO_HAVE_INT64_T) && (MOO_SIZEOF_OOW_T >= 8)
 		case 8:
 			((struct st_int64_t*)&rawptr[offset])->v = w; 
 			return 0;
 	#endif
 
-	#if defined(MOO_HAVE_INT128_T) && (MOO_SIZEOF_OOW_T >= MOO_SIZEOF_INT128_T)
+	#if defined(MOO_HAVE_INT128_T) && (MOO_SIZEOF_OOW_T >= 16)
 		case 16:
 			((struct st_int128_t*)&rawptr[offset])->v = w; 
 			return 0;
diff --git a/moo/lib/utl.c b/moo/lib/utl.c
index 774e549..a6bb754 100644
--- a/moo/lib/utl.c
+++ b/moo/lib/utl.c
@@ -26,6 +26,45 @@
 
 #include "moo-prv.h"
 
+/* ----------------------------------------------------------------------- */
+int moo_log2_for_pow2 (moo_oow_t pow2v)
+{
+#if defined(MOO_HAVE_UINT32_T) && (MOO_SIZEOF_OOW_T == 4)
+
+	static const int debruijn[32] = 
+	{
+		0, 1, 28, 2, 29, 14, 24, 3,
+		30, 22, 20, 15, 25, 17, 4, 8, 
+		31, 27, 13, 23, 21, 19, 16, 7,
+		26, 12, 18, 6, 11, 5, 10, 9
+	};
+
+	return debruijn[(moo_uint32_t)(pow2v * 0x077CB531u) >> 27];
+
+#elif defined(MOO_HAVE_UINT64_T) && (MOO_SIZEOF_OOW_T == 8)
+
+	static const int debruijn[64] = 
+	{
+		0, 1,  2, 53,  3,  7, 54, 27,
+		4, 38, 41,  8, 34, 55, 48, 28,
+		62,  5, 39, 46, 44, 42, 22,  9,
+		24, 35, 59, 56, 49, 18, 29, 11,
+		63, 52,  6, 26, 37, 40, 33, 47,
+		61, 45, 43, 21, 23, 58, 17, 10,
+		51, 25, 36, 32, 60, 20, 57, 16,
+		50, 31, 19, 15, 30, 14, 13, 12
+	};
+
+	return debruijn[(moo_uint64_t)(pow2v * 0x022fdd63cc95386dllu) >> 58];
+
+#else
+	int i;
+	for (i = -1; pow2v; i++) pow2v >>= 1;
+	return (i == -1) ? 0 : i;
+
+#endif
+}
+
 /* ----------------------------------------------------------------------- */
 
 #if defined(MOO_HAVE_UINT16_T)