Use GCC builtins for clz operation

1 files changed, 26 insertions, 1 deletions

diff --git a/src/lib/utils/bit_ops.h b/src/lib/utils/bit_ops.h
index aa41db391..c7e401492 100644
--- a/src/lib/utils/bit_ops.h
+++ b/src/lib/utils/bit_ops.h
@@ -107,11 +107,36 @@ inline size_t ctz(T n)
 template<>
 inline size_t ctz(uint32_t n)
    {
+   if(n == 0)
+      return 32;
    return __builtin_ctz(n);
    }
 
-#endif
+template<>
+inline size_t ctz(uint64_t n)
+   {
+   if(n == 0)
+      return 64;
+   return __builtin_ctzll(n);
+   }
 
+template<>
+inline size_t high_bit(uint32_t x)
+   {
+   if(x == 0)
+      return 0;
+   return (32 - __builtin_clz(x));
+   }
+
+template<>
+inline size_t high_bit(uint64_t x)
+   {
+   if(x == 0)
+      return 0;
+   return (64 - __builtin_clzll(x));
+   }
+
+#endif
 
 template<typename T>
 size_t ceil_log2(T x)