Use bitmath builtins for FindLastBit

src/core/bitmath_func.cpp

@@ -62,7 +62,7 @@ uint8 FindFirstBit64(uint64 x)
  * @param x The value to search
  * @return The position of the last bit set
  */
-uint8 FindLastBit(uint64 x)
+uint8 FindLastBit64(uint64 x)
 {
 	if (x == 0) return 0;
 

src/core/bitmath_func.hpp

@@ -240,7 +240,32 @@ static inline uint8 FindFirstBit(T value)
 #endif
 }
 
-uint8 FindLastBit(uint64 x);
+/**
+ * Search the last set bit in an integer variable.
+ *
+ * @param value The value to search
+ * @return The position of the last bit set, or 0 when value is 0
+ */
+template <typename T>
+static inline uint8 FindLastBit(T value)
+{
+	static_assert(sizeof(T) <= sizeof(unsigned long long));
+#ifdef WITH_BITMATH_BUILTINS
+	if (value == 0) return 0;
+	typename std::make_unsigned<T>::type unsigned_value = value;
+	if (sizeof(T) <= sizeof(unsigned int)) {
+		return __builtin_clz(1) - __builtin_clz(unsigned_value);
+	} else if (sizeof(T) == sizeof(unsigned long)) {
+		return __builtin_clzl(1) - __builtin_clzl(unsigned_value);
+	} else {
+		return __builtin_clzll(1) - __builtin_ctzll(unsigned_value);
+	}
+#else
+	extern uint8 FindLastBit64(uint64 x);
+	return FindLastBit64(value);
+#endif
+}
+
 
 /**
  * Finds the position of the first non-zero bit in an integer.

src/graph_gui.cpp

@@ -459,7 +459,7 @@ protected:
 						 * integer, so at about 31 bits because of the sign bit, the
 						 * least significant bits are removed.
 						 */
-						int mult_range = FindLastBit(x_axis_offset) + FindLastBit(abs(datapoint));
+						int mult_range = FindLastBit<uint64>(x_axis_offset) + FindLastBit<uint64>(abs(datapoint));
 						int reduce_range = std::max(mult_range - 31, 0);
 
 						/* Handle negative values differently (don't shift sign) */