gpu: Rewrite GPU command list processing with DmaPusher class.

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

src/video_core/dma_pusher.cpp

@@ -0,0 +1,110 @@
+// Copyright 2018 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include "core/core.h"
+#include "core/memory.h"
+#include "video_core/dma_pusher.h"
+#include "video_core/engines/maxwell_3d.h"
+#include "video_core/gpu.h"
+
+namespace Tegra {
+
+DmaPusher::DmaPusher(GPU& gpu) : gpu(gpu) {}
+
+DmaPusher::~DmaPusher() = default;
+
+void DmaPusher::DispatchCalls() {
+    // On entering GPU code, assume all memory may be touched by the ARM core.
+    gpu.Maxwell3D().dirty_flags.OnMemoryWrite();
+
+    while (Core::System::GetInstance().IsPoweredOn()) {
+        if (!Step()) {
+            break;
+        }
+    }
+}
+
+bool DmaPusher::Step() {
+    if (dma_get != dma_put) {
+        // Push buffer non-empty, read a word
+        const CommandHeader command_header{
+            Memory::Read32(*gpu.MemoryManager().GpuToCpuAddress(dma_get))};
+
+        dma_get += sizeof(u32);
+
+        if (!non_main) {
+            dma_mget = dma_get;
+        }
+
+        // now, see if we're in the middle of a command
+        if (dma_state.length_pending) {
+            // Second word of long non-inc methods command - method count
+            dma_state.length_pending = 0;
+            dma_state.method_count = command_header.method_count_;
+        } else if (dma_state.method_count) {
+            // Data word of methods command
+            CallMethod(command_header.argument);
+
+            if (!dma_state.non_incrementing) {
+                dma_state.method++;
+            }
+
+            if (dma_increment_once) {
+                dma_state.non_incrementing = true;
+            }
+
+            dma_state.method_count--;
+        } else {
+            // No command active - this is the first word of a new one
+            switch (command_header.mode) {
+            case SubmissionMode::Increasing:
+                SetState(command_header);
+                dma_state.non_incrementing = false;
+                dma_increment_once = false;
+                break;
+            case SubmissionMode::NonIncreasing:
+                SetState(command_header);
+                dma_state.non_incrementing = true;
+                dma_increment_once = false;
+                break;
+            case SubmissionMode::Inline:
+                dma_state.method = command_header.method;
+                dma_state.subchannel = command_header.subchannel;
+                CallMethod(command_header.arg_count);
+                dma_state.non_incrementing = true;
+                dma_increment_once = false;
+                break;
+            case SubmissionMode::IncreaseOnce:
+                SetState(command_header);
+                dma_state.non_incrementing = false;
+                dma_increment_once = true;
+                break;
+            }
+        }
+    } else if (ib_enable && !dma_pushbuffer.empty()) {
+        // Current pushbuffer empty, but we have more IB entries to read
+        const CommandListHeader& command_list_header{dma_pushbuffer.front()};
+        dma_get = command_list_header.addr;
+        dma_put = dma_get + command_list_header.size * sizeof(u32);
+        non_main = command_list_header.is_non_main;
+        dma_pushbuffer.pop();
+    } else {
+        // Otherwise, pushbuffer empty and IB empty or nonexistent - nothing to do
+        return {};
+    }
+
+    return true;
+}
+
+void DmaPusher::SetState(const CommandHeader& command_header) {
+    dma_state.method = command_header.method;
+    dma_state.subchannel = command_header.subchannel;
+    dma_state.method_count = command_header.method_count;
+}
+
+void DmaPusher::CallMethod(u32 argument) const {
+    gpu.CallMethod({dma_state.method, argument, dma_state.subchannel, dma_state.method_count});
+}
+
+} // namespace Tegra