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BitField: Make mostly constexpr capable 

Makes the constructor and retrieval functions constexpr.
This commit is contained in:
Lioncash 2017-03-23 10:53:13 -04:00
parent 4b5995a6e0
commit caef08988e
1 changed files with 15 additions and 16 deletions
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31
Source/Core/Common/BitField.h
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@ -121,7 +121,7 @@ private:
public:
// Force default constructor to be created
// so that we can use this within unions
BitField() = default;
constexpr BitField() = default;
// We explicitly delete the copy assignment operator here, because the
// default copy assignment would copy the full storage value, rather than
@ -139,20 +139,8 @@ public:
return *this;
}
__forceinline T Value() const
{
if (std::numeric_limits<T>::is_signed)
{
std::size_t shift = 8 * sizeof(T) - bits;
return (T)((storage << (shift - position)) >> shift);
}
else
{
return (T)((storage & GetMask()) >> position);
}
}
__forceinline operator T() const { return Value(); }
constexpr T Value() const { return Value(std::is_signed<T>()); }
constexpr operator T() const { return Value(); }
private:
// StorageType is T for non-enum types and the underlying type of T if
// T is an enumeration. Note that T is wrapped within an enable_if in the
@ -161,10 +149,21 @@ private:
typedef typename std::conditional<std::is_enum<T>::value, std::underlying_type<T>,
std::enable_if<true, T>>::type::type StorageType;
constexpr T Value(std::true_type) const
{
using shift_amount = std::integral_constant<size_t, 8 * sizeof(T) - bits>;
return static_cast<T>((storage << (shift_amount() - position)) >> shift_amount());
}
constexpr T Value(std::false_type) const
{
return static_cast<T>((storage & GetMask()) >> position);
}
// Unsigned version of StorageType
typedef typename std::make_unsigned<StorageType>::type StorageTypeU;
__forceinline StorageType GetMask() const
static constexpr StorageType GetMask()
{
return (((StorageTypeU)~0) >> (8 * sizeof(T) - bits)) << position;
}