move ARM64 JIT backend here

src/dolphin/BitUtils.h

@@ -0,0 +1,254 @@
+// Copyright 2017 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <climits>
+#include <cstddef>
+#include <cstring>
+#include <type_traits>
+
+namespace Common
+{
+///
+/// Retrieves the size of a type in bits.
+///
+/// @tparam T Type to get the size of.
+///
+/// @return the size of the type in bits.
+///
+template <typename T>
+constexpr size_t BitSize() noexcept
+{
+  return sizeof(T) * CHAR_BIT;
+}
+
+///
+/// Extracts a bit from a value.
+///
+/// @param  src The value to extract a bit from.
+/// @param  bit The bit to extract.
+///
+/// @tparam T   The type of the value.
+///
+/// @return The extracted bit.
+///
+template <typename T>
+constexpr T ExtractBit(const T src, const size_t bit) noexcept
+{
+  return (src >> bit) & static_cast<T>(1);
+}
+
+///
+/// Extracts a bit from a value.
+///
+/// @param  src The value to extract a bit from.
+///
+/// @tparam bit The bit to extract.
+/// @tparam T   The type of the value.
+///
+/// @return The extracted bit.
+///
+template <size_t bit, typename T>
+constexpr T ExtractBit(const T src) noexcept
+{
+  static_assert(bit < BitSize<T>(), "Specified bit must be within T's bit width.");
+
+  return ExtractBit(src, bit);
+}
+
+///
+/// Extracts a range of bits from a value.
+///
+/// @param  src    The value to extract the bits from.
+/// @param  begin  The beginning of the bit range. This is inclusive.
+/// @param  end    The ending of the bit range. This is inclusive.
+///
+/// @tparam T      The type of the value.
+/// @tparam Result The returned result type. This is the unsigned analog
+///                of a signed type if a signed type is passed as T.
+///
+/// @return The extracted bits.
+///
+template <typename T, typename Result = std::make_unsigned_t<T>>
+constexpr Result ExtractBits(const T src, const size_t begin, const size_t end) noexcept
+{
+  return static_cast<Result>(((static_cast<Result>(src) << ((BitSize<T>() - 1) - end)) >>
+                              (BitSize<T>() - end + begin - 1)));
+}
+
+///
+/// Extracts a range of bits from a value.
+///
+/// @param  src    The value to extract the bits from.
+///
+/// @tparam begin  The beginning of the bit range. This is inclusive.
+/// @tparam end    The ending of the bit range. This is inclusive.
+/// @tparam T      The type of the value.
+/// @tparam Result The returned result type. This is the unsigned analog
+///                of a signed type if a signed type is passed as T.
+///
+/// @return The extracted bits.
+///
+template <size_t begin, size_t end, typename T, typename Result = std::make_unsigned_t<T>>
+constexpr Result ExtractBits(const T src) noexcept
+{
+  static_assert(begin < end, "Beginning bit must be less than the ending bit.");
+  static_assert(begin < BitSize<T>(), "Beginning bit is larger than T's bit width.");
+  static_assert(end < BitSize<T>(), "Ending bit is larger than T's bit width.");
+
+  return ExtractBits<T, Result>(src, begin, end);
+}
+
+///
+/// Rotates a value left (ROL).
+///
+/// @param  value  The value to rotate.
+/// @param  amount The number of bits to rotate the value.
+/// @tparam T      An unsigned type.
+///
+/// @return The rotated value.
+///
+template <typename T>
+constexpr T RotateLeft(const T value, size_t amount) noexcept
+{
+  static_assert(std::is_unsigned<T>(), "Can only rotate unsigned types left.");
+
+  amount %= BitSize<T>();
+
+  if (amount == 0)
+    return value;
+
+  return static_cast<T>((value << amount) | (value >> (BitSize<T>() - amount)));
+}
+
+///
+/// Rotates a value right (ROR).
+///
+/// @param  value  The value to rotate.
+/// @param  amount The number of bits to rotate the value.
+/// @tparam T      An unsigned type.
+///
+/// @return The rotated value.
+///
+template <typename T>
+constexpr T RotateRight(const T value, size_t amount) noexcept
+{
+  static_assert(std::is_unsigned<T>(), "Can only rotate unsigned types right.");
+
+  amount %= BitSize<T>();
+
+  if (amount == 0)
+    return value;
+
+  return static_cast<T>((value >> amount) | (value << (BitSize<T>() - amount)));
+}
+
+///
+/// Verifies whether the supplied value is a valid bit mask of the form 0b00...0011...11.
+/// Both edge cases of all zeros and all ones are considered valid masks, too.
+///
+/// @param  mask The mask value to test for validity.
+///
+/// @tparam T    The type of the value.
+///
+/// @return A bool indicating whether the mask is valid.
+///
+template <typename T>
+constexpr bool IsValidLowMask(const T mask) noexcept
+{
+  static_assert(std::is_integral<T>::value, "Mask must be an integral type.");
+  static_assert(std::is_unsigned<T>::value, "Signed masks can introduce hard to find bugs.");
+
+  // Can be efficiently determined without looping or bit counting. It's the counterpart
+  // to https://graphics.stanford.edu/~seander/bithacks.html#DetermineIfPowerOf2
+  // and doesn't require special casing either edge case.
+  return (mask & (mask + 1)) == 0;
+}
+
+///
+/// Reinterpret objects of one type as another by bit-casting between object representations.
+///
+/// @remark This is the example implementation of std::bit_cast which is to be included
+///         in C++2a. See http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0476r2.html
+///         for more details. The only difference is this variant is not constexpr,
+///         as the mechanism for bit_cast requires a compiler built-in to have that quality.
+///
+/// @param source The source object to convert to another representation.
+///
+/// @tparam To   The type to reinterpret source as.
+/// @tparam From The initial type representation of source.
+///
+/// @return The representation of type From as type To.
+///
+/// @pre Both To and From types must be the same size
+/// @pre Both To and From types must satisfy the TriviallyCopyable concept.
+///
+template <typename To, typename From>
+inline To BitCast(const From& source) noexcept
+{
+  static_assert(sizeof(From) == sizeof(To),
+                "BitCast source and destination types must be equal in size.");
+  static_assert(std::is_trivially_copyable<From>(),
+                "BitCast source type must be trivially copyable.");
+  static_assert(std::is_trivially_copyable<To>(),
+                "BitCast destination type must be trivially copyable.");
+
+  std::aligned_storage_t<sizeof(To), alignof(To)> storage;
+  std::memcpy(&storage, &source, sizeof(storage));
+  return reinterpret_cast<To&>(storage);
+}
+
+template <typename T, typename PtrType>
+class BitCastPtrType
+{
+public:
+  static_assert(std::is_trivially_copyable<PtrType>(),
+                "BitCastPtr source type must be trivially copyable.");
+  static_assert(std::is_trivially_copyable<T>(),
+                "BitCastPtr destination type must be trivially copyable.");
+
+  explicit BitCastPtrType(PtrType* ptr) : m_ptr(ptr) {}
+
+  // Enable operator= only for pointers to non-const data
+  template <typename S>
+  inline typename std::enable_if<std::is_same<S, T>() && !std::is_const<PtrType>()>::type
+  operator=(const S& source)
+  {
+    std::memcpy(m_ptr, &source, sizeof(source));
+  }
+
+  inline operator T() const
+  {
+    T result;
+    std::memcpy(&result, m_ptr, sizeof(result));
+    return result;
+  }
+
+private:
+  PtrType* m_ptr;
+};
+
+// Provides an aliasing-safe alternative to reinterpret_cast'ing pointers to structs
+// Conversion constructor and operator= provided for a convenient syntax.
+// Usage: MyStruct s = BitCastPtr<MyStruct>(some_ptr);
+// BitCastPtr<MyStruct>(some_ptr) = s;
+template <typename T, typename PtrType>
+inline auto BitCastPtr(PtrType* ptr) noexcept -> BitCastPtrType<T, PtrType>
+{
+  return BitCastPtrType<T, PtrType>{ptr};
+}
+
+template <typename T>
+void SetBit(T& value, size_t bit_number, bool bit_value)
+{
+  static_assert(std::is_unsigned<T>(), "SetBit is only sane on unsigned types.");
+
+  if (bit_value)
+    value |= (T{1} << bit_number);
+  else
+    value &= ~(T{1} << bit_number);
+}
+
+}  // namespace Common