gpu: Rewrite GPU command list processing with DmaPusher class.

- More accurate impl., fixes Undertale (among other games).

src/video_core/dma_pusher.h

@@ -0,0 +1,95 @@
+// Copyright 2018 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <queue>
+
+#include "common/bit_field.h"
+#include "common/common_types.h"
+#include "video_core/memory_manager.h"
+
+namespace Tegra {
+
+enum class SubmissionMode : u32 {
+    IncreasingOld = 0,
+    Increasing = 1,
+    NonIncreasingOld = 2,
+    NonIncreasing = 3,
+    Inline = 4,
+    IncreaseOnce = 5
+};
+
+struct CommandListHeader {
+    union {
+        u64 raw;
+        BitField<0, 40, GPUVAddr> addr;
+        BitField<41, 1, u64> is_non_main;
+        BitField<42, 21, u64> size;
+    };
+};
+static_assert(sizeof(CommandListHeader) == sizeof(u64), "CommandListHeader is incorrect size");
+
+union CommandHeader {
+    u32 argument;
+    BitField<0, 13, u32> method;
+    BitField<0, 24, u32> method_count_;
+    BitField<13, 3, u32> subchannel;
+    BitField<16, 13, u32> arg_count;
+    BitField<16, 13, u32> method_count;
+    BitField<29, 3, SubmissionMode> mode;
+};
+static_assert(std::is_standard_layout_v<CommandHeader>, "CommandHeader is not standard layout");
+static_assert(sizeof(CommandHeader) == sizeof(u32), "CommandHeader has incorrect size!");
+
+class GPU;
+
+/**
+ * The DmaPusher class implements DMA submission to FIFOs, providing an area of memory that the
+ * emulated app fills with commands and tells PFIFO to process. The pushbuffers are then assembled
+ * into a "command stream" consisting of 32-bit words that make up "commands".
+ * See https://envytools.readthedocs.io/en/latest/hw/fifo/dma-pusher.html#fifo-dma-pusher for
+ * details on this implementation.
+ */
+class DmaPusher {
+public:
+    explicit DmaPusher(GPU& gpu);
+    ~DmaPusher();
+
+    void Push(const CommandListHeader& command_list_header) {
+        dma_pushbuffer.push(command_list_header);
+    }
+
+    void DispatchCalls();
+
+private:
+    bool Step();
+
+    void SetState(const CommandHeader& command_header);
+
+    void CallMethod(u32 argument) const;
+
+    GPU& gpu;
+
+    std::queue<CommandListHeader> dma_pushbuffer;
+
+    struct DmaState {
+        u32 method;            ///< Current method
+        u32 subchannel;        ///< Current subchannel
+        u32 method_count;      ///< Current method count
+        u32 length_pending;    ///< Large NI command length pending
+        bool non_incrementing; ///< Current command’s NI flag
+    };
+
+    DmaState dma_state{};
+    bool dma_increment_once{};
+
+    GPUVAddr dma_put{};   ///< pushbuffer current end address
+    GPUVAddr dma_get{};   ///< pushbuffer current read address
+    GPUVAddr dma_mget{};  ///< main pushbuffer last read address
+    bool ib_enable{true}; ///< IB mode enabled
+    bool non_main{};      ///< non-main pushbuffer active
+};
+
+} // namespace Tegra