Where possible use compiler builtins for CountBits and FindFirstBit.

src/core/bitmath_func.hpp

@@ -185,6 +185,18 @@ static inline T ToggleBit(T &x, const uint8 y)
 	return x = (T)(x ^ ((T)1U << y));
 }
 
+#ifdef WITH_BITMATH_BUILTINS
+
+#define FIND_FIRST_BIT(x) FindFirstBit(x)
+
+inline uint8 FindFirstBit(uint32 x)
+{
+	if (x == 0) return 0;
+
+	return __builtin_ctz(x);
+}
+
+#else
 
 /** Lookup table to check which bit is set in a 6 bit variable */
 extern const uint8 _ffb_64[64];
@@ -201,6 +213,12 @@ extern const uint8 _ffb_64[64];
  */
 #define FIND_FIRST_BIT(x) _ffb_64[(x)]
 
+uint8 FindFirstBit(uint32 x);
+
+#endif
+
+uint8 FindLastBit(uint64 x);
+
 /**
  * Finds the position of the first non-zero bit in an integer.
  *
@@ -224,9 +242,6 @@ static inline uint8 FindFirstBit2x64(const int value)
 	}
 }
 
-uint8 FindFirstBit(uint32 x);
-uint8 FindLastBit(uint64 x);
-
 /**
  * Clear the first bit in an integer.
  *
@@ -252,6 +267,15 @@ static inline T KillFirstBit(T value)
 template <typename T>
 static inline uint CountBits(T value)
 {
+#ifdef WITH_BITMATH_BUILTINS
+	if (sizeof(T) == sizeof(unsigned int)) {
+		return __builtin_popcount(value);
+	} else if (sizeof(T) == sizeof(unsigned long)) {
+		return __builtin_popcountl(value);
+	} else {
+		return __builtin_popcountll(value);
+	}
+#else
 	uint num;
 
 	/* This loop is only called once for every bit set by clearing the lowest
@@ -264,6 +288,7 @@ static inline uint CountBits(T value)
 	}
 
 	return num;
+#endif
 }
 
 /**