diff --git a/lib/common/bitstream.h b/lib/common/bitstream.h
index 72b4f7fa9..84b6062ff 100644
--- a/lib/common/bitstream.h
+++ b/lib/common/bitstream.h
@@ -143,10 +143,16 @@ MEM_STATIC unsigned BIT_highbit32 (U32 val)
     {
 #   if defined(_MSC_VER)   /* Visual */
 #       if STATIC_BMI2 == 1
-		return _lzcnt_u32(val) ^ 31;
+            return _lzcnt_u32(val) ^ 31;
 #       else
-		unsigned long r = 0;
-		return _BitScanReverse(&r, val) ? (unsigned)r : 0;
+            if (val != 0) {
+                unsigned long r;
+                _BitScanReverse(&r, val);
+                return (unsigned)r;
+            } else {
+                /* Should not reach this code path */
+                __assume(0);
+            }
 #       endif
 #   elif defined(__GNUC__) && (__GNUC__ >= 3)   /* Use GCC Intrinsic */
         return __builtin_clz (val) ^ 31;
diff --git a/lib/common/entropy_common.c b/lib/common/entropy_common.c
index 6ba1f2209..3ac00255f 100644
--- a/lib/common/entropy_common.c
+++ b/lib/common/entropy_common.c
@@ -43,8 +43,14 @@ static U32 FSE_ctz(U32 val)
     assert(val != 0);
     {
 #   if defined(_MSC_VER)   /* Visual */
-        unsigned long r=0;
-        return _BitScanForward(&r, val) ? (unsigned)r : 0;
+        if (val != 0) {
+            unsigned long r;
+            _BitScanForward(&r, val);
+            return (unsigned)r;
+        } else {
+            /* Should not reach this code path */
+            __assume(0);
+        }
 #   elif defined(__GNUC__) && (__GNUC__ >= 3)   /* GCC Intrinsic */
         return __builtin_ctz(val);
 #   elif defined(__ICCARM__)    /* IAR Intrinsic */
diff --git a/lib/common/zstd_internal.h b/lib/common/zstd_internal.h
index aaf7d4665..efd7360a0 100644
--- a/lib/common/zstd_internal.h
+++ b/lib/common/zstd_internal.h
@@ -358,8 +358,14 @@ MEM_STATIC U32 ZSTD_highbit32(U32 val)   /* compress, dictBuilder, decodeCorpus
 #       if STATIC_BMI2 == 1
             return _lzcnt_u32(val)^31;
 #       else
-            unsigned long r=0;
-            return _BitScanReverse(&r, val) ? (unsigned)r : 0;
+            if (val != 0) {
+                unsigned long r;
+                _BitScanReverse(&r, val);
+                return (unsigned)r;
+            } else {
+                /* Should not reach this code path */
+                __assume(0);
+            }
 #       endif
 #   elif defined(__GNUC__) && (__GNUC__ >= 3)   /* GCC Intrinsic */
         return __builtin_clz (val) ^ 31;
@@ -379,10 +385,10 @@ MEM_STATIC U32 ZSTD_highbit32(U32 val)   /* compress, dictBuilder, decodeCorpus
 }
 
 /**
- * Computes CTZ on a U64.
- * This will be slow on 32-bit mode, and on unsupported compilers.
- * If you need this function to be fast (because it is hot) expand
- * support.
+ * Counts the number of trailing zeros of a `size_t`.
+ * Most compilers should support CTZ as a builtin. A backup
+ * implementation is provided if the builtin isn't supported, but
+ * it may not be terribly efficient.
  */
 MEM_STATIC unsigned ZSTD_countTrailingZeros(size_t val)
 {
@@ -391,8 +397,14 @@ MEM_STATIC unsigned ZSTD_countTrailingZeros(size_t val)
 #           if STATIC_BMI2
                 return _tzcnt_u64(val);
 #           else
-                unsigned long r = 0;
-                return _BitScanForward64( &r, (U64)val ) ? (unsigned)(r >> 3) : 0;
+                if (val != 0) {
+                    unsigned long r;
+                    _BitScanForward64(&r, (U64)val);
+                    return (unsigned)r;
+                } else {
+                    /* Should not reach this code path */
+                    __assume(0);
+                }
 #           endif
 #       elif defined(__GNUC__) && (__GNUC__ >= 4)
             return __builtin_ctzll((U64)val);
@@ -409,10 +421,16 @@ MEM_STATIC unsigned ZSTD_countTrailingZeros(size_t val)
 #       endif
     } else { /* 32 bits */
 #       if defined(_MSC_VER)
-            unsigned long r=0;
-            return _BitScanForward( &r, (U32)val ) ? (unsigned)(r >> 3) : 0;
+            if (val != 0) {
+                unsigned long r;
+                _BitScanForward(&r, (U32)val);
+                return (unsigned)r;
+            } else {
+                /* Should not reach this code path */
+                __assume(0);
+            }
 #       elif defined(__GNUC__) && (__GNUC__ >= 3)
-            return (__builtin_ctz((U32)val) >> 3);
+            return __builtin_ctz((U32)val);
 #       else
             static const int DeBruijnBytePos[32] = {  0,  1, 28,  2, 29, 14, 24,  3,
                                                      30, 22, 20, 15, 25, 17,  4,  8,
diff --git a/lib/compress/zstd_compress_internal.h b/lib/compress/zstd_compress_internal.h
index 03b5e33b0..9e4c1ac17 100644
--- a/lib/compress/zstd_compress_internal.h
+++ b/lib/compress/zstd_compress_internal.h
@@ -672,8 +672,14 @@ static unsigned ZSTD_NbCommonBytes (size_t val)
 #           if STATIC_BMI2
                 return _tzcnt_u64(val) >> 3;
 #           else
-                unsigned long r = 0;
-                return _BitScanForward64( &r, (U64)val ) ? (unsigned)(r >> 3) : 0;
+                if (val != 0) {
+                    unsigned long r;
+                    _BitScanForward64(&r, (U64)val);
+                    return (unsigned)(r >> 3);
+                } else {
+                    /* Should not reach this code path */
+                    __assume(0);
+                }
 #           endif
 #       elif defined(__GNUC__) && (__GNUC__ >= 4)
             return (__builtin_ctzll((U64)val) >> 3);
@@ -690,8 +696,14 @@ static unsigned ZSTD_NbCommonBytes (size_t val)
 #       endif
         } else { /* 32 bits */
 #       if defined(_MSC_VER)
-            unsigned long r=0;
-            return _BitScanForward( &r, (U32)val ) ? (unsigned)(r >> 3) : 0;
+            if (val != 0) {
+                unsigned long r;
+                _BitScanForward(&r, (U32)val);
+                return (unsigned)(r >> 3);
+            } else {
+                /* Should not reach this code path */
+                __assume(0);
+            }
 #       elif defined(__GNUC__) && (__GNUC__ >= 3)
             return (__builtin_ctz((U32)val) >> 3);
 #       else
@@ -708,8 +720,14 @@ static unsigned ZSTD_NbCommonBytes (size_t val)
 #           if STATIC_BMI2
 			    return _lzcnt_u64(val) >> 3;
 #           else
-			    unsigned long r = 0;
-			    return _BitScanReverse64(&r, (U64)val) ? (unsigned)(r >> 3) : 0;
+                if (val != 0) {
+                    unsigned long r;
+                    _BitScanReverse64(&r, (U64)val);
+                    return (unsigned)(r >> 3);
+                } else {
+                    /* Should not reach this code path */
+                    __assume(0);
+                }
 #           endif
 #       elif defined(__GNUC__) && (__GNUC__ >= 4)
             return (__builtin_clzll(val) >> 3);
@@ -723,8 +741,14 @@ static unsigned ZSTD_NbCommonBytes (size_t val)
 #       endif
         } else { /* 32 bits */
 #       if defined(_MSC_VER)
-            unsigned long r = 0;
-            return _BitScanReverse( &r, (unsigned long)val ) ? (unsigned)(r >> 3) : 0;
+            if (val != 0) {
+                unsigned long r;
+                _BitScanReverse(&r, (unsigned long)val);
+                return (unsigned)(r >> 3);
+            } else {
+                /* Should not reach this code path */
+                __assume(0);
+            }
 #       elif defined(__GNUC__) && (__GNUC__ >= 3)
             return (__builtin_clz((U32)val) >> 3);
 #       else
diff --git a/lib/compress/zstd_lazy.c b/lib/compress/zstd_lazy.c
index 1846684c3..78cc5b09b 100644
--- a/lib/compress/zstd_lazy.c
+++ b/lib/compress/zstd_lazy.c
@@ -883,8 +883,14 @@ typedef U64 ZSTD_VecMask;   /* Clarifies when we are interacting with a U64 repr
 static U32 ZSTD_VecMask_next(ZSTD_VecMask val) {
     assert(val != 0);
 #   if defined(_MSC_VER) && defined(_WIN64)
-    unsigned long r=0;
-    return _BitScanForward64(&r, val) ? (U32)r : 0; /* _BitScanForward64 not defined outside of x86/64 */
+        if (val != 0) {
+            unsigned long r;
+            _BitScanForward64(&r, val);
+            return (U32)(r);
+        } else {
+            /* Should not reach this code path */
+            __assume(0);
+        }
 #   elif (defined(__GNUC__) && ((__GNUC__ > 3) || ((__GNUC__ == 3) && (__GNUC_MINOR__ >= 4))))
     if (sizeof(size_t) == 4) {
         U32 mostSignificantWord = (U32)(val >> 32);
diff --git a/lib/dictBuilder/zdict.c b/lib/dictBuilder/zdict.c
index 9edc77fe8..d93b202e7 100644
--- a/lib/dictBuilder/zdict.c
+++ b/lib/dictBuilder/zdict.c
@@ -135,9 +135,14 @@ static unsigned ZDICT_NbCommonBytes (size_t val)
     if (MEM_isLittleEndian()) {
         if (MEM_64bits()) {
 #       if defined(_MSC_VER) && defined(_WIN64)
-            unsigned long r = 0;
-            _BitScanForward64( &r, (U64)val );
-            return (unsigned)(r>>3);
+            if (val != 0) {
+                unsigned long r;
+                _BitScanForward64(&r, (U64)val);
+                return (unsigned)(r >> 3);
+            } else {
+                /* Should not reach this code path */
+                __assume(0);
+            }
 #       elif defined(__GNUC__) && (__GNUC__ >= 3)
             return (unsigned)(__builtin_ctzll((U64)val) >> 3);
 #       else
@@ -146,9 +151,14 @@ static unsigned ZDICT_NbCommonBytes (size_t val)
 #       endif
         } else { /* 32 bits */
 #       if defined(_MSC_VER)
-            unsigned long r=0;
-            _BitScanForward( &r, (U32)val );
-            return (unsigned)(r>>3);
+            if (val != 0) {
+                unsigned long r;
+                _BitScanForward(&r, (U32)val);
+                return (unsigned)(r >> 3);
+            } else {
+                /* Should not reach this code path */
+                __assume(0);
+            }
 #       elif defined(__GNUC__) && (__GNUC__ >= 3)
             return (unsigned)(__builtin_ctz((U32)val) >> 3);
 #       else
@@ -159,9 +169,14 @@ static unsigned ZDICT_NbCommonBytes (size_t val)
     } else {  /* Big Endian CPU */
         if (MEM_64bits()) {
 #       if defined(_MSC_VER) && defined(_WIN64)
-            unsigned long r = 0;
-            _BitScanReverse64( &r, val );
-            return (unsigned)(r>>3);
+            if (val != 0) {
+                unsigned long r;
+                _BitScanReverse64(&r, val);
+                return (unsigned)(r >> 3);
+            } else {
+                /* Should not reach this code path */
+                __assume(0);
+            }
 #       elif defined(__GNUC__) && (__GNUC__ >= 3)
             return (unsigned)(__builtin_clzll(val) >> 3);
 #       else
@@ -174,9 +189,14 @@ static unsigned ZDICT_NbCommonBytes (size_t val)
 #       endif
         } else { /* 32 bits */
 #       if defined(_MSC_VER)
-            unsigned long r = 0;
-            _BitScanReverse( &r, (unsigned long)val );
-            return (unsigned)(r>>3);
+            if (val != 0) {
+                unsigned long r;
+                _BitScanReverse(&r, (unsigned long)val);
+                return (unsigned)(r >> 3);
+            } else {
+                /* Should not reach this code path */
+                __assume(0);
+            }
 #       elif defined(__GNUC__) && (__GNUC__ >= 3)
             return (unsigned)(__builtin_clz((U32)val) >> 3);
 #       else
diff --git a/lib/legacy/zstd_v01.c b/lib/legacy/zstd_v01.c
index 7ab554797..6be9c8105 100644
--- a/lib/legacy/zstd_v01.c
+++ b/lib/legacy/zstd_v01.c
@@ -343,8 +343,7 @@ FORCE_INLINE unsigned FSE_highbit32 (U32 val)
 {
 #   if defined(_MSC_VER)   /* Visual */
     unsigned long r;
-    _BitScanReverse ( &r, val );
-    return (unsigned) r;
+    return _BitScanReverse(&r, val) ? (unsigned)r : 0;
 #   elif defined(__GNUC__) && (GCC_VERSION >= 304)   /* GCC Intrinsic */
     return __builtin_clz (val) ^ 31;
 #   else   /* Software version */
diff --git a/lib/legacy/zstd_v02.c b/lib/legacy/zstd_v02.c
index 89fdc7169..f26b99bc8 100644
--- a/lib/legacy/zstd_v02.c
+++ b/lib/legacy/zstd_v02.c
@@ -353,9 +353,8 @@ MEM_STATIC size_t BIT_readBitsFast(BIT_DStream_t* bitD, unsigned nbBits);
 MEM_STATIC unsigned BIT_highbit32 (U32 val)
 {
 #   if defined(_MSC_VER)   /* Visual */
-    unsigned long r=0;
-    _BitScanReverse ( &r, val );
-    return (unsigned) r;
+    unsigned long r;
+    return _BitScanReverse(&r, val) ? (unsigned)r : 0;
 #   elif defined(__GNUC__) && (__GNUC__ >= 3)   /* Use GCC Intrinsic */
     return __builtin_clz (val) ^ 31;
 #   else   /* Software version */
diff --git a/lib/legacy/zstd_v03.c b/lib/legacy/zstd_v03.c
index 5262d515a..744bde515 100644
--- a/lib/legacy/zstd_v03.c
+++ b/lib/legacy/zstd_v03.c
@@ -356,9 +356,8 @@ MEM_STATIC size_t BIT_readBitsFast(BIT_DStream_t* bitD, unsigned nbBits);
 MEM_STATIC unsigned BIT_highbit32 (U32 val)
 {
 #   if defined(_MSC_VER)   /* Visual */
-    unsigned long r=0;
-    _BitScanReverse ( &r, val );
-    return (unsigned) r;
+    unsigned long r;
+    return _BitScanReverse(&r, val) ? (unsigned)r : 0;
 #   elif defined(__GNUC__) && (__GNUC__ >= 3)   /* Use GCC Intrinsic */
     return __builtin_clz (val) ^ 31;
 #   else   /* Software version */
diff --git a/lib/legacy/zstd_v04.c b/lib/legacy/zstd_v04.c
index bee1b99dd..4d336b59f 100644
--- a/lib/legacy/zstd_v04.c
+++ b/lib/legacy/zstd_v04.c
@@ -627,9 +627,8 @@ MEM_STATIC size_t BIT_readBitsFast(BIT_DStream_t* bitD, unsigned nbBits);
 MEM_STATIC unsigned BIT_highbit32 (U32 val)
 {
 #   if defined(_MSC_VER)   /* Visual */
-    unsigned long r=0;
-    _BitScanReverse ( &r, val );
-    return (unsigned) r;
+    unsigned long r;
+    return _BitScanReverse(&r, val) ? (unsigned)r : 0;
 #   elif defined(__GNUC__) && (__GNUC__ >= 3)   /* Use GCC Intrinsic */
     return __builtin_clz (val) ^ 31;
 #   else   /* Software version */
diff --git a/lib/legacy/zstd_v05.c b/lib/legacy/zstd_v05.c
index eb8966bb4..bc293661e 100644
--- a/lib/legacy/zstd_v05.c
+++ b/lib/legacy/zstd_v05.c
@@ -756,9 +756,8 @@ MEM_STATIC size_t BITv05_readBitsFast(BITv05_DStream_t* bitD, unsigned nbBits);
 MEM_STATIC unsigned BITv05_highbit32 (U32 val)
 {
 #   if defined(_MSC_VER)   /* Visual */
-    unsigned long r=0;
-    _BitScanReverse ( &r, val );
-    return (unsigned) r;
+    unsigned long r;
+    return _BitScanReverse(&r, val) ? (unsigned)r : 0;
 #   elif defined(__GNUC__) && (__GNUC__ >= 3)   /* Use GCC Intrinsic */
     return __builtin_clz (val) ^ 31;
 #   else   /* Software version */
diff --git a/lib/legacy/zstd_v06.c b/lib/legacy/zstd_v06.c
index fcb16d4d8..7d6a35922 100644
--- a/lib/legacy/zstd_v06.c
+++ b/lib/legacy/zstd_v06.c
@@ -860,9 +860,8 @@ MEM_STATIC size_t BITv06_readBitsFast(BITv06_DStream_t* bitD, unsigned nbBits);
 MEM_STATIC unsigned BITv06_highbit32 ( U32 val)
 {
 #   if defined(_MSC_VER)   /* Visual */
-    unsigned long r=0;
-    _BitScanReverse ( &r, val );
-    return (unsigned) r;
+    unsigned long r;
+    return _BitScanReverse(&r, val) ? (unsigned)r : 0;
 #   elif defined(__GNUC__) && (__GNUC__ >= 3)   /* Use GCC Intrinsic */
     return __builtin_clz (val) ^ 31;
 #   else   /* Software version */
diff --git a/lib/legacy/zstd_v07.c b/lib/legacy/zstd_v07.c
index 0d0e46609..1449ef3ab 100644
--- a/lib/legacy/zstd_v07.c
+++ b/lib/legacy/zstd_v07.c
@@ -530,9 +530,8 @@ MEM_STATIC size_t BITv07_readBitsFast(BITv07_DStream_t* bitD, unsigned nbBits);
 MEM_STATIC unsigned BITv07_highbit32 (U32 val)
 {
 #   if defined(_MSC_VER)   /* Visual */
-    unsigned long r=0;
-    _BitScanReverse ( &r, val );
-    return (unsigned) r;
+    unsigned long r;
+    return _BitScanReverse(&r, val) ? (unsigned)r : 0;
 #   elif defined(__GNUC__) && (__GNUC__ >= 3)   /* Use GCC Intrinsic */
     return __builtin_clz (val) ^ 31;
 #   else   /* Software version */