diff --git a/src/libFLAC/bitmath.c b/src/libFLAC/bitmath.c
index 043bb490..189977c6 100644
--- a/src/libFLAC/bitmath.c
+++ b/src/libFLAC/bitmath.c
@@ -58,10 +58,16 @@
  * ilog2(17) = 4
  * ilog2(18) = 4
  */
+
+#ifndef __GNUC__
+
+/* For GNUC, use static inline version in include/private/bitmath.h. */
+
 unsigned FLAC__bitmath_ilog2(FLAC__uint32 v)
 {
-	unsigned l = 0;
-	FLAC__ASSERT(v > 0);
+ 	unsigned l = 0;
+    if (v == 0)
+		return 0;
 	while(v >>= 1)
 		l++;
 	return l;
@@ -70,11 +76,13 @@ unsigned FLAC__bitmath_ilog2(FLAC__uint32 v)
 unsigned FLAC__bitmath_ilog2_wide(FLAC__uint64 v)
 {
 	unsigned l = 0;
-	FLAC__ASSERT(v > 0);
+    if (v == 0)
+		return 0;
 	while(v >>= 1)
 		l++;
 	return l;
 }
+#endif
 
 /* An example of what FLAC__bitmath_silog2() computes:
  *
diff --git a/src/libFLAC/bitreader.c b/src/libFLAC/bitreader.c
index c3edd163..ef24951c 100644
--- a/src/libFLAC/bitreader.c
+++ b/src/libFLAC/bitreader.c
@@ -55,14 +55,24 @@ typedef FLAC__uint32 brword;
 #else
 #define SWAP_BE_WORD_TO_HOST(x) ENDSWAP_32(x)
 #endif
+
+#if defined(__GNUC__)
+/*  "int __builtin_clz (unsigned int x) If x is 0, the result is undefined" */
+static inline uint32_t
+COUNT_ZERO_MSBS (uint32_t word)
+{
+	if (word == 0)
+		return 32;
+	return __builtin_clz (word);
+}
+#else
 /* counts the # of zero MSBs in a word */
 #define COUNT_ZERO_MSBS(word) ( \
 	(word) <= 0xffff ? \
 		( (word) <= 0xff? byte_to_unary_table[word] + 24 : byte_to_unary_table[(word) >> 8] + 16 ) : \
 		( (word) <= 0xffffff? byte_to_unary_table[word >> 16] + 8 : byte_to_unary_table[(word) >> 24] ) \
 )
-/* this alternate might be slightly faster on some systems/compilers: */
-#define COUNT_ZERO_MSBS2(word) ( (word) <= 0xff ? byte_to_unary_table[word] + 24 : ((word) <= 0xffff ? byte_to_unary_table[(word) >> 8] + 16 : ((word) <= 0xffffff ? byte_to_unary_table[(word) >> 16] + 8 : byte_to_unary_table[(word) >> 24])) )
+#endif
 
 
 /*
diff --git a/src/libFLAC/include/private/bitmath.h b/src/libFLAC/include/private/bitmath.h
index 67b70bad..b3d18f47 100644
--- a/src/libFLAC/include/private/bitmath.h
+++ b/src/libFLAC/include/private/bitmath.h
@@ -34,8 +34,30 @@
 
 #include "FLAC/ordinals.h"
 
+
+#if defined(__GNUC__)
+
+static inline unsigned FLAC__bitmath_ilog2(FLAC__uint32 v)
+{
+    if (v == 0)
+		return 0;
+    return sizeof(FLAC__uint32) * __CHAR_BIT__  - 1 - __builtin_clz(v);
+}
+
+static inline unsigned FLAC__bitmath_ilog2_wide(FLAC__uint64 v)
+{
+    if (v == 0)
+		return 0;
+    return sizeof(FLAC__uint64) * __CHAR_BIT__ - 1 - __builtin_clzll(v);
+}
+
+#else
+
 unsigned FLAC__bitmath_ilog2(FLAC__uint32 v);
 unsigned FLAC__bitmath_ilog2_wide(FLAC__uint64 v);
+
+#endif
+
 unsigned FLAC__bitmath_silog2(int v);
 unsigned FLAC__bitmath_silog2_wide(FLAC__int64 v);