dma_pushbuffer: Optimize to avoid loop and copy on Push.

src/video_core/dma_pusher.cpp

@@ -23,6 +23,8 @@ void DmaPusher::DispatchCalls() {
     // On entering GPU code, assume all memory may be touched by the ARM core.
     gpu.Maxwell3D().dirty_flags.OnMemoryWrite();
 
+    dma_pushbuffer_subindex = 0;
+
     while (Core::System::GetInstance().IsPoweredOn()) {
         if (!Step()) {
             break;
@@ -89,11 +91,17 @@ bool DmaPusher::Step() {
         }
     } 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()};
+        const CommandList& command_list{dma_pushbuffer.front()};
+        const CommandListHeader& command_list_header{command_list[dma_pushbuffer_subindex++]};
         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();
+
+        if (dma_pushbuffer_subindex >= command_list.size()) {
+            // We've gone through the current list, remove it from the queue
+            dma_pushbuffer.pop();
+            dma_pushbuffer_subindex = 0;
+        }
     } else {
         // Otherwise, pushbuffer empty and IB empty or nonexistent - nothing to do
         return {};

src/video_core/dma_pusher.h

@@ -4,6 +4,7 @@
 
 #pragma once
 
+#include <vector>
 #include <queue>
 
 #include "common/bit_field.h"
@@ -45,6 +46,8 @@ static_assert(sizeof(CommandHeader) == sizeof(u32), "CommandHeader has incorrect
 
 class GPU;
 
+using CommandList = std::vector<Tegra::CommandListHeader>;
+
 /**
  * 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
@@ -57,8 +60,8 @@ public:
     explicit DmaPusher(GPU& gpu);
     ~DmaPusher();
 
-    void Push(const CommandListHeader& command_list_header) {
-        dma_pushbuffer.push(command_list_header);
+    void Push(CommandList&& entries) {
+        dma_pushbuffer.push(std::move(entries));
     }
 
     void DispatchCalls();
@@ -72,7 +75,8 @@ private:
 
     GPU& gpu;
 
-    std::queue<CommandListHeader> dma_pushbuffer;
+    std::queue<CommandList> dma_pushbuffer; ///< Queue of command lists to be processed
+    std::size_t dma_pushbuffer_subindex{};  ///< Index within a command list within the pushbuffer
 
     struct DmaState {
         u32 method;            ///< Current method