video_core: Add basic command list processing (#117)

src/common/bit_field.h

@@ -0,0 +1,166 @@
+// SPDX-FileCopyrightText: 2014 Tony Wasserka
+// SPDX-FileCopyrightText: 2014 Dolphin Emulator Project
+// SPDX-License-Identifier: BSD-3-Clause AND GPL-2.0-or-later
+
+#pragma once
+
+#include <cstddef>
+#include <limits>
+#include <type_traits>
+
+/*
+ * Abstract bitfield class
+ *
+ * Allows endianness-independent access to individual bitfields within some raw
+ * integer value. The assembly generated by this class is identical to the
+ * usage of raw bitfields, so it's a perfectly fine replacement.
+ *
+ * For BitField<X,Y,Z>, X is the distance of the bitfield to the LSB of the
+ * raw value, Y is the length in bits of the bitfield. Z is an integer type
+ * which determines the sign of the bitfield. Z must have the same size as the
+ * raw integer.
+ *
+ *
+ * General usage:
+ *
+ * Create a new union with the raw integer value as a member.
+ * Then for each bitfield you want to expose, add a BitField member
+ * in the union. The template parameters are the bit offset and the number
+ * of desired bits.
+ *
+ * Changes in the bitfield members will then get reflected in the raw integer
+ * value and vice-versa.
+ *
+ *
+ * Sample usage:
+ *
+ * union SomeRegister
+ * {
+ *     u32 hex;
+ *
+ *     BitField<0,7,u32> first_seven_bits;     // unsigned
+ *     BitField<7,8,u32> next_eight_bits;      // unsigned
+ *     BitField<3,15,s32> some_signed_fields;  // signed
+ * };
+ *
+ * This is equivalent to the little-endian specific code:
+ *
+ * union SomeRegister
+ * {
+ *     u32 hex;
+ *
+ *     struct
+ *     {
+ *         u32 first_seven_bits : 7;
+ *         u32 next_eight_bits : 8;
+ *     };
+ *     struct
+ *     {
+ *         u32 : 3; // padding
+ *         s32 some_signed_fields : 15;
+ *     };
+ * };
+ *
+ *
+ * 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).
+ */
+#pragma pack(1)
+template <std::size_t Position, std::size_t Bits, typename T>
+struct BitField {
+private:
+    // UnderlyingType 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
+    // former case to workaround compile errors which arise when using
+    // std::underlying_type<T>::type directly.
+    using UnderlyingType = typename std::conditional_t<std::is_enum_v<T>, std::underlying_type<T>,
+                                                       std::enable_if<true, T>>::type;
+
+    // We store the value as the unsigned type to avoid undefined behaviour on value shifting
+    using StorageType = std::make_unsigned_t<UnderlyingType>;
+
+public:
+    /// Constants to allow limited introspection of fields if needed
+    static constexpr std::size_t position = Position;
+    static constexpr std::size_t bits = Bits;
+    static constexpr StorageType mask = (((StorageType)~0) >> (8 * sizeof(T) - bits)) << position;
+
+    /**
+     * Formats a value by masking and shifting it according to the field parameters. A value
+     * containing several bitfields can be assembled by formatting each of their values and ORing
+     * the results together.
+     */
+    [[nodiscard]] static constexpr StorageType FormatValue(const T& value) {
+        return (static_cast<StorageType>(value) << position) & mask;
+    }
+
+    /**
+     * Extracts a value from the passed storage. In most situations prefer use the member functions
+     * (such as Value() or operator T), but this can be used to extract a value from a bitfield
+     * union in a constexpr context.
+     */
+    [[nodiscard]] static constexpr T ExtractValue(const StorageType& storage) {
+        if constexpr (std::numeric_limits<UnderlyingType>::is_signed) {
+            std::size_t shift = 8 * sizeof(T) - bits;
+            return static_cast<T>(static_cast<UnderlyingType>(storage << (shift - position)) >>
+                                  shift);
+        } else {
+            return static_cast<T>((storage & mask) >> position);
+        }
+    }
+
+    // This constructor and assignment operator might be considered ambiguous:
+    // Would they initialize the storage or just the bitfield?
+    // Hence, delete them. Use the Assign method to set bitfield values!
+    BitField(T val) = delete;
+    BitField& operator=(T val) = delete;
+
+    constexpr BitField() noexcept = default;
+
+    constexpr BitField(const BitField&) noexcept = default;
+    constexpr BitField& operator=(const BitField&) noexcept = default;
+
+    constexpr BitField(BitField&&) noexcept = default;
+    constexpr BitField& operator=(BitField&&) noexcept = default;
+
+    [[nodiscard]] constexpr operator T() const {
+        return Value();
+    }
+
+    constexpr void Assign(const T& value) {
+        storage = (static_cast<StorageType>(storage) & ~mask) | FormatValue(value);
+    }
+
+    [[nodiscard]] constexpr T Value() const {
+        return ExtractValue(storage);
+    }
+
+    [[nodiscard]] constexpr explicit operator bool() const {
+        return Value() != 0;
+    }
+
+private:
+    StorageType storage;
+
+    static_assert(bits + position <= 8 * sizeof(T), "Bitfield out of range");
+
+    // And, you know, just in case people specify something stupid like bits=position=0x80000000
+    static_assert(position < 8 * sizeof(T), "Invalid position");
+    static_assert(bits <= 8 * sizeof(T), "Invalid number of bits");
+    static_assert(bits > 0, "Invalid number of bits");
+    static_assert(std::is_trivially_copyable_v<T>, "T must be trivially copyable in a BitField");
+};
+#pragma pack()

src/common/native_clock.cpp

@@ -13,8 +13,8 @@
 namespace Common {
 
 NativeClock::NativeClock()
-    : rdtsc_frequency{EstimateRDTSCFrequency()}, ns_rdtsc_factor{GetFixedPoint64Factor(
-                                                     std::nano::den, rdtsc_frequency)},
+    : rdtsc_frequency{EstimateRDTSCFrequency()},
+      ns_rdtsc_factor{GetFixedPoint64Factor(std::nano::den, rdtsc_frequency)},
       us_rdtsc_factor{GetFixedPoint64Factor(std::micro::den, rdtsc_frequency)},
       ms_rdtsc_factor{GetFixedPoint64Factor(std::milli::den, rdtsc_frequency)} {}