Merge pull request #270 from neobrain/bitfield_fixes

Bitfield fixes

Source/Core/Common/BitField.h

@@ -36,6 +36,8 @@
 #include <limits>
 #include <type_traits>
 
+#include "Common.h"
+
 /*
  * Abstract bitfield class
  *
@@ -92,13 +94,23 @@
  *
  * Caveats:
  *
+ * 1)
  * BitField provides automatic casting from and to the storage type where
  * appropriate. However, when using non-typesafe functions like printf, an
  * explicit cast must be performed on the BitField object to make sure it gets
  * passed correctly, e.g.:
  * printf("Value: %d", (s32)some_register.some_signed_fields);
  *
+ * 2)
+ * Not really a caveat, but potentially irritating: This class is used in some
+ * packed structures that do not guarantee proper alignment. Therefore we have
+ * to use #pragma pack here not to pack the members of the class, but instead
+ * to break GCC's assumption that the members of the class are aligned on
+ * sizeof(StorageType).
+ * TODO(neobrain): Confirm that this is a proper fix and not just masking
+ * symptoms.
  */
+#pragma pack(1)
 template<std::size_t position, std::size_t bits, typename T>
 struct BitField
 {
@@ -113,13 +125,13 @@ public:
 	// so that we can use this within unions
 	BitField() = default;
 
-	BitField& operator=(T val)
+	__forceinline BitField& operator=(T val)
 	{
 		storage = (storage & ~GetMask()) | ((val << position) & GetMask());
 		return *this;
 	}
 
-	operator T() const
+	__forceinline operator T() const
 	{
 		if (std::numeric_limits<T>::is_signed)
 		{
@@ -144,7 +156,7 @@ private:
 	// Unsigned version of StorageType
 	typedef typename std::make_unsigned<StorageType>::type StorageTypeU;
 
-	StorageType GetMask() const
+	__forceinline StorageType GetMask() const
 	{
 		return ((~(StorageTypeU)0) >> (8*sizeof(T) - bits)) << position;
 	}
@@ -158,3 +170,4 @@ private:
 	static_assert(bits <= 8 * sizeof(T), "Invalid number of bits");
 	static_assert(bits > 0, "Invalid number of bits");
 };
+#pragma pack()