ReadSetting with the default is a convenience function reading
settings, not for use in an internal environment. It tries to manage
the default value of a setting.
The current BitField implementation requires the use of the union, which makes it both non-constexpr (due to accessing inactive union members), and prevents the usage of smaller types and enums, reducing its flexibility.
Furthermore, BitField is not trivially copyable (and by extension, not trivial).
Moreover, it is not well documented that BitField performs automatic sign extension on signed integers, as a recent PR made an assumption that these signed integers were zero extended.
These considerations resulted in this new BitField implementation, which uses macros to generate functions for accessing / setting bitfield values.
2 macros are provided:
`YUZU_RO_BITFIELD` for read-only BitFields, which generates a member function that directly returns the specified type.
`YUZU_BITFIELD`, which generates a member function that returns a `BitFieldHelper` class which allows setting the value using `operator=` or `Set()`, and performs implicit conversion to the specified type.
Types:
The following type tags are added:
Automatic type deduction:
AutoUInt, AutoSignExtSInt, AutoZeroExtSInt, AutoFloat
Automatic type deduction selects the smallest type that contains at least the specified NumBits bits.
However, in testing, MSVC is pretty bad at optimizing smaller-than-32-bit accesses, so it may be advisable to specify 32 bit types in performance sensitive code.
Signed Integers:
SignExtSInt<>, ZeroExtSInt<>
The new SignExtSInt and ZeroExtSInt are mandatory type tags for signed integers to explicitly specify whether to sign extend (preserving the sign and value) or zero extend the bitfield value.
These changes have sacrificed compatibility with `_be` types. This is a worthwhile sacrifice as we do not have usages of these types in BitField.
Example usage:
```cpp
struct MyTestStruct {
u32 raw;
YUZU_RO_BITFIELD(0, 3, AutoUInt, field0);
YUZU_BITFIELD(3, 4, AutoSignExtSInt, field1);
YUZU_BITFIELD(7, 5, ZeroExtSInt<s16>, field2);
YUZU_RO_BITFIELD(12, 1, bool, flag0);
};
MyTestStruct s{0x1234567};
s.field1() = -1;
s.field2() = -2;
fmt::print("field0={}, field1={}, field2={}, flag0={}", s.field0(), s.field1(), s.field2(), s.flag0());
```
Narr the Reg