diff --git a/lib/insn.c b/lib/insn.c
index f7c06565..23bbabfc 100644
--- a/lib/insn.c
+++ b/lib/insn.c
@@ -235,9 +235,6 @@ wasm_fmax(double a, double b)
 static uint32_t
 clz(uint32_t v)
 {
-        if (v == 0) {
-                return 32;
-        }
 #if __has_builtin(__builtin_clz)
         return __builtin_clz(v);
 #else
@@ -245,7 +242,7 @@ clz(uint32_t v)
         uint32_t u = v;
         while ((u & 0x80000000) == 0) {
                 cnt++;
-                u << 1;
+                u <<= 1;
         }
         return cnt;
 #endif
@@ -254,9 +251,6 @@ clz(uint32_t v)
 static uint32_t
 ctz(uint32_t v)
 {
-        if (v == 0) {
-                return 32;
-        }
 #if __has_builtin(__builtin_ctz)
         return __builtin_ctz(v);
 #else
@@ -270,6 +264,24 @@ ctz(uint32_t v)
 #endif
 }
 
+static uint32_t
+wasm_clz(uint32_t v)
+{
+        if (v == 0) {
+                return 32;
+        }
+        return clz(v);
+}
+
+static uint32_t
+wasm_ctz(uint32_t v)
+{
+        if (v == 0) {
+                return 32;
+        }
+        return ctz(v);
+}
+
 static uint32_t
 wasm_popcount(uint32_t v)
 {
@@ -287,29 +299,29 @@ wasm_popcount(uint32_t v)
 }
 
 static uint64_t
-clz64(uint64_t v)
+wasm_clz64(uint64_t v)
 {
         if (v == 0) {
                 return 64;
         }
         uint32_t high = v >> 32;
         if (high == 0) {
-                return 32 + __builtin_clz(v);
+                return 32 + clz(v);
         }
-        return __builtin_clz(high);
+        return clz(high);
 }
 
 static uint64_t
-ctz64(uint64_t v)
+wasm_ctz64(uint64_t v)
 {
         if (v == 0) {
                 return 64;
         }
         uint32_t low = (uint32_t)v;
         if (low == 0) {
-                return 32 + __builtin_ctz((uint32_t)(v >> 32));
+                return 32 + ctz((uint32_t)(v >> 32));
         }
-        return __builtin_ctz(low);
+        return ctz(low);
 }
 
 static uint64_t
diff --git a/lib/insn_impl_base.h b/lib/insn_impl_base.h
index 6b310bba..cb6b0d47 100644
--- a/lib/insn_impl_base.h
+++ b/lib/insn_impl_base.h
@@ -383,8 +383,8 @@ CMPOP(i64_le_u, 64, uint64_t, <=)
 CMPOP(i64_ge_s, 64, int64_t, >=)
 CMPOP(i64_ge_u, 64, uint64_t, >=)
 
-BITCOUNTOP(i32_clz, i32, clz)
-BITCOUNTOP(i32_ctz, i32, ctz)
+BITCOUNTOP(i32_clz, i32, wasm_clz)
+BITCOUNTOP(i32_ctz, i32, wasm_ctz)
 BITCOUNTOP(i32_popcnt, i32, wasm_popcount)
 
 BINOP(i32_add, i, 32, ADD)
@@ -406,8 +406,8 @@ BINOP(i32_shr_u, i, 32, SHR_U)
 BINOP(i32_rotl, i, 32, ROTL)
 BINOP(i32_rotr, i, 32, ROTR)
 
-BITCOUNTOP(i64_clz, i64, clz64)
-BITCOUNTOP(i64_ctz, i64, ctz64)
+BITCOUNTOP(i64_clz, i64, wasm_clz64)
+BITCOUNTOP(i64_ctz, i64, wasm_ctz64)
 BITCOUNTOP(i64_popcnt, i64, wasm_popcount64)
 
 BINOP(i64_add, i, 64, ADD)