[GPU] Add hard FPS limit without vsync

src/xenia/gpu/gpu_flags.cc

@@ -22,6 +22,13 @@ DEFINE_bool(vsync, true, "Enable VSYNC.", "GPU");
 
 DEFINE_uint64(vsync_fps, 60, "VSYNC frames per second", "GPU");
 
+DEFINE_uint64(hard_fps, 60,
+    "Hard FPS lock, ignored when vsync is used. "
+    "Game will never exceed this value", "GPU");
+
+DEFINE_bool(hard_fps_enable, false,
+    "Enable hard FPS lock, ignored if vsync is enabled", "GPU");
+
 DEFINE_bool(
     gpu_allow_invalid_fetch_constants, true,
     "Allow texture and vertex fetch constants with invalid type - generally "

src/xenia/gpu/gpu_flags.h

@@ -20,6 +20,9 @@ DECLARE_bool(vsync);
 
 DECLARE_uint64(vsync_fps);
 
+DECLARE_uint64(hard_fps);
+DECLARE_bool(hard_fps_enable);
+
 DECLARE_bool(gpu_allow_invalid_fetch_constants);
 
 DECLARE_bool(half_pixel_offset);

src/xenia/gpu/graphics_system.cc

@@ -133,8 +133,14 @@ X_STATUS GraphicsSystem::Setup(cpu::Processor* processor,
               threading::NanoSleep(estimated_nanoseconds);
             }
           }
+          
           if (!cvars::vsync) {
-            xe::threading::Sleep(std::chrono::milliseconds(1));
+            if (cvars::hard_fps_enable) {
+              uint64_t hard_frame_sleep_time = 1000000000 / cvars::hard_fps;
+              xe::threading::NanoSleep(hard_frame_sleep_time);
+            } else {
+              xe::threading::Sleep(std::chrono::milliseconds(1));
+            }
           }
         }
         return 0;