Runahead system

config.def.h

@@ -589,6 +589,12 @@ static const float slowmotion_ratio = 3.0;
 /* Maximum fast forward ratio. */
 static const float fastforward_ratio = 0.0;
 
+/* Run core logic one or more frames ahead then load the state back to reduce perceived input lag. */
+static const unsigned run_ahead_frames = 1;
+
+/* When using the Run Ahead feature, use a secondary instance of the core. */
+static const bool run_ahead_secondary_instance = true;
+
 /* Enable stdin/network command interface. */
 static const bool network_cmd_enable = false;
 static const uint16_t network_cmd_port = 55355;

configuration.c

@@ -1220,6 +1220,8 @@ static struct config_bool_setting *populate_settings_bool(settings_t *settings,
    SETTING_BOOL("ui_menubar_enable",             &settings->bools.ui_menubar_enable, true, true, false);
    SETTING_BOOL("suspend_screensaver_enable",    &settings->bools.ui_suspend_screensaver_enable, true, true, false);
    SETTING_BOOL("rewind_enable",                 &settings->bools.rewind_enable, true, rewind_enable, false);
+   SETTING_BOOL("run_ahead_enabled",             &settings->bools.run_ahead_enabled, true, false, false);
+   SETTING_BOOL("run_ahead_secondary_instance",  &settings->bools.run_ahead_secondary_instance, true, false, false);
    SETTING_BOOL("audio_sync",                    &settings->bools.audio_sync, true, audio_sync, false);
    SETTING_BOOL("video_shader_enable",           &settings->bools.video_shader_enable, true, shader_enable, false);
    SETTING_BOOL("video_shader_watch_files",      &settings->bools.video_shader_watch_files, true, video_shader_watch_files, false);
@@ -1513,6 +1515,8 @@ static struct config_uint_setting *populate_settings_uint(settings_t *settings,
    SETTING_UINT("video_msg_bgcolor_green",        &settings->uints.video_msg_bgcolor_green, true, message_bgcolor_green, false);
    SETTING_UINT("video_msg_bgcolor_blue",        &settings->uints.video_msg_bgcolor_blue, true, message_bgcolor_blue, false);
 
+   SETTING_UINT("run_ahead_frames",           &settings->uints.run_ahead_frames, true, 1,  false);
+
    *size = count;
 
    return tmp;

configuration.h

@@ -223,6 +223,8 @@ typedef struct settings
       bool playlist_entry_remove;
       bool playlist_entry_rename;
       bool rewind_enable;
+      bool run_ahead_enabled;
+      bool run_ahead_secondary_instance;
       bool pause_nonactive;
       bool block_sram_overwrite;
       bool savestate_auto_index;
@@ -380,6 +382,8 @@ typedef struct settings
       unsigned input_remap_ids[MAX_USERS][RARCH_CUSTOM_BIND_LIST_END];
 
       unsigned led_map[MAX_LEDS];
+
+      unsigned run_ahead_frames;
    } uints;
 
    struct

core.h

@@ -170,6 +170,9 @@ bool core_set_poll_type(unsigned *type);
 /* Runs the core for one frame. */
 bool core_run(void);
 
+/* Runs the core for one frame, but does not trigger any input polling */
+bool core_run_no_input_polling(void);
+
 bool core_init(void);
 
 bool core_deinit(void *data);

core_impl.c

@@ -44,6 +44,9 @@
 #include "gfx/video_driver.h"
 #include "audio/audio_driver.h"
 
+#include "runahead/copy_load_info.h"
+#include "runahead/secondary_core.h"
+
 struct                     retro_callbacks retro_ctx;
 struct                     retro_core_t current_core;
 
@@ -262,6 +265,9 @@ bool core_set_controller_port_device(retro_ctx_controller_info_t *pad)
 {
    if (!pad)
       return false;
+
+   remember_controller_port_device(pad->port, pad->device);
+
    current_core.retro_set_controller_port_device(pad->port, pad->device);
    return true;
 }
@@ -277,6 +283,8 @@ bool core_get_memory(retro_ctx_memory_info_t *info)
 
 bool core_load_game(retro_ctx_load_content_info_t *load_info)
 {
+   set_load_content_info(load_info);
+
    bool contentless = false;
    bool is_inited   = false;
 
@@ -424,6 +432,12 @@ bool core_run(void)
    return true;
 }
 
+bool core_run_no_input_polling(void)
+{
+   current_core.retro_run();
+   return true;
+}
+
 bool core_load(unsigned poll_type_behavior)
 {
    current_core.poll_type = poll_type_behavior;

dynamic.c

@@ -66,9 +66,11 @@
 #include "msg_hash.h"
 #include "verbosity.h"
 
+#include "runahead/secondary_core.h"
+
 #ifdef HAVE_DYNAMIC
 #define SYMBOL(x) do { \
-   function_t func = dylib_proc(lib_handle, #x); \
+   function_t func = dylib_proc(lib_handle_local, #x); \
    memcpy(&current_core->x, &func, sizeof(func)); \
    if (current_core->x == NULL) { RARCH_ERR("Failed to load symbol: \"%s\"\n", #x); retroarch_fail(1, "init_libretro_sym()"); } \
 } while (0)
@@ -383,14 +385,32 @@ bool libretro_get_system_info(const char *path,
  * Setup libretro callback symbols. Returns true on success,
  * or false if symbols could not be loaded.
  **/
-static bool load_symbols(enum rarch_core_type type, struct retro_core_t *current_core)
+bool init_libretro_sym_custom(enum rarch_core_type type, struct retro_core_t *current_core, const char *lib_path, dylib_t *lib_handle_p)
 {
+   /* the library handle for use with the SYMBOL macro */
+   dylib_t lib_handle_local;
    switch (type)
    {
       case CORE_TYPE_PLAIN:
 #ifdef HAVE_DYNAMIC
-         if (!load_dynamic_core())
-            return false;
+
+         if (lib_path == NULL || lib_handle_p == NULL)
+         {
+            if (!load_dynamic_core())
+               return false;
+            lib_handle_local = lib_handle;
+         }
+         else
+         {
+            /* for a secondary core, we already have a primary library loaded, so we can skip some checks and just load the library */
+            retro_assert(lib_path != NULL && lib_handle_p != NULL);
+            lib_handle_local = dylib_load(lib_path);
+            if (lib_handle_local == NULL)
+            {
+               return false;
+            }
+            *lib_handle_p = lib_handle_local;
+         }
 #endif
 
          SYMBOL(retro_init);
@@ -615,6 +635,11 @@ static bool load_symbols(enum rarch_core_type type, struct retro_core_t *current
    return true;
 }
 
+static bool load_symbols(enum rarch_core_type type, struct retro_core_t *current_core)
+{
+   return init_libretro_sym_custom(type, current_core, NULL, NULL);
+}
+
 /**
  * init_libretro_sym:
  * @type                        : Type of core to be loaded.
@@ -634,6 +659,8 @@ bool init_libretro_sym(enum rarch_core_type type, struct retro_core_t *current_c
    if (!load_symbols(type, current_core))
       return false;
 
+   /* remember last core type created, so creating a secondary core will know what core type to use */
+   set_last_core_type(type);
    return true;
 }
 

dynamic.h

@@ -20,6 +20,7 @@
 #include <boolean.h>
 #include <retro_common_api.h>
 #include <libretro.h>
+#include <dynamic/dylib.h>
 
 #include "core_type.h"
 
@@ -132,6 +133,8 @@ bool libretro_get_shared_context(void);
 bool init_libretro_sym(enum rarch_core_type type,
       struct retro_core_t *core);
 
+bool init_libretro_sym_custom(enum rarch_core_type type, struct retro_core_t *current_core, const char *lib_path, dylib_t *lib_handle_p);
+
 /**
  * uninit_libretro_sym:
  *

griffin/griffin.c

@@ -56,6 +56,9 @@ COMPATIBILITY
 
 #include "../libretro-common/compat/compat_fnmatch.c"
 #include "../libretro-common/compat/fopen_utf8.c"
+#if defined(HAVE_DYNAMIC) && HAVE_DYNAMIC
+#include "../libretro-common/compat/unlink_utf8.c"
+#endif
 #include "../libretro-common/memmap/memalign.c"
 
 /*============================================================
@@ -1252,6 +1255,13 @@ MENU
 #include "../libretro-common/net/net_http_parse.c"
 #endif
 
+#include "../runahead/mem_util.c"
+#include "../runahead/secondary_core.c"
+#include "../runahead/run_ahead.c"
+#include "../runahead/copy_load_info.c"
+#include "../runahead/dirty_input.c"
+#include "../runahead/mylist.c"
+
 /*============================================================
 DEPENDENCIES
 ============================================================ */

intl/msg_hash_lbl.h

@@ -989,6 +989,12 @@ MSG_HASH(MENU_ENUM_LABEL_SHUTDOWN,
       "shutdown")
 MSG_HASH(MENU_ENUM_LABEL_SLOWMOTION_RATIO,
       "slowmotion_ratio")
+MSG_HASH(MENU_ENUM_LABEL_RUN_AHEAD_ENABLED,
+      "run_ahead_enabled")
+MSG_HASH(MENU_ENUM_LABEL_RUN_AHEAD_SECONDARY_INSTANCE,
+      "run_ahead_secondary_instance")
+MSG_HASH(MENU_ENUM_LABEL_RUN_AHEAD_FRAMES,
+      "run_ahead_frames")
 MSG_HASH(MENU_ENUM_LABEL_SORT_SAVEFILES_ENABLE,
       "sort_savefiles_enable")
 MSG_HASH(MENU_ENUM_LABEL_SORT_SAVESTATES_ENABLE,

intl/msg_hash_us.h

@@ -1445,6 +1445,12 @@ MSG_HASH(MENU_ENUM_LABEL_VALUE_SHUTDOWN,
       "Shutdown")
 MSG_HASH(MENU_ENUM_LABEL_VALUE_SLOWMOTION_RATIO,
       "Slow-Motion Ratio")
+MSG_HASH(MENU_ENUM_LABEL_VALUE_RUN_AHEAD_ENABLED,
+      "Run-Ahead to Reduce Latency")
+MSG_HASH(MENU_ENUM_LABEL_VALUE_RUN_AHEAD_FRAMES,
+      "Number of Frames to Run Ahead")
+MSG_HASH(MENU_ENUM_LABEL_VALUE_RUN_AHEAD_SECONDARY_INSTANCE,
+      "Runahead Use Second Instance")
 MSG_HASH(MENU_ENUM_LABEL_VALUE_SORT_SAVEFILES_ENABLE,
       "Sort Saves In Folders")
 MSG_HASH(MENU_ENUM_LABEL_VALUE_SORT_SAVESTATES_ENABLE,
@@ -2720,6 +2726,18 @@ MSG_HASH(
       MENU_ENUM_SUBLABEL_SLOWMOTION_RATIO,
       "When in slow motion, content will slow down by the factor specified/set."
       )
+MSG_HASH(
+      MENU_ENUM_SUBLABEL_RUN_AHEAD_ENABLED,
+      "Run core logic one or more frames ahead then load the state back to reduce perceived input lag."
+      )
+MSG_HASH(
+      MENU_ENUM_SUBLABEL_RUN_AHEAD_FRAMES,
+      "The number of frames to run ahead. Causes gameplay issues such as jitter if you exceed the number of lag frames internal to the game."
+      )
+MSG_HASH(
+      MENU_ENUM_SUBLABEL_RUN_AHEAD_SECONDARY_INSTANCE,
+      "Use a second instance of the RetroArch core to run ahead. Prevents audio problems due to loading state."
+      )
 MSG_HASH(
       MENU_ENUM_SUBLABEL_REWIND_ENABLE,
       "Enable rewinding. This will take a performance hit when playing."

libretro-common/compat/unlink_utf8.c

@@ -0,0 +1,30 @@
+#include <compat/unlink_utf8.h>
+#include <encodings/utf.h>
+#include "boolean.h"
+#include <malloc.h>
+
+#if defined(_WIN32_WINNT) && _WIN32_WINNT < 0x0500 || defined(_XBOX)
+#ifndef LEGACY_WIN32
+#define LEGACY_WIN32
+#endif
+#endif
+
+#ifdef _WIN32
+
+#define NOMINMAX
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+
+bool unlink_utf8(const char * filename)
+{
+#if defined(LEGACY_WIN32)
+	bool result = DeleteFileA(filename_w);
+#else
+	wchar_t * filename_w = utf8_to_utf16_string_alloc(filename);
+	bool result = DeleteFileW(filename_w);
+	free(filename_w);
+#endif
+	return result;
+}
+
+#endif

libretro-common/include/compat/unlink_utf8.h

@@ -0,0 +1,23 @@
+#ifndef __UNLINK_UTF8_H
+#define __UNLINK_UTF8_H
+
+#include "boolean.h"
+
+#ifdef _WIN32
+
+#if __cplusplus
+extern "C"
+{
+#endif
+
+bool unlink_utf8(const char * filename);
+
+#if __cplusplus
+}
+#endif
+
+#else
+#include <unistd.h>
+#define unlink_utf8 unlink
+#endif
+#endif

menu/cbs/menu_cbs_sublabel.c

@@ -172,6 +172,9 @@ default_sublabel_macro(action_bind_sublabel_savestate_auto_index,          MENU_
 default_sublabel_macro(action_bind_sublabel_block_sram_overwrite,          MENU_ENUM_SUBLABEL_BLOCK_SRAM_OVERWRITE)
 default_sublabel_macro(action_bind_sublabel_fastforward_ratio,             MENU_ENUM_SUBLABEL_FASTFORWARD_RATIO)
 default_sublabel_macro(action_bind_sublabel_slowmotion_ratio,              MENU_ENUM_SUBLABEL_SLOWMOTION_RATIO)
+default_sublabel_macro(action_bind_sublabel_run_ahead_enabled,             MENU_ENUM_SUBLABEL_RUN_AHEAD_ENABLED)
+default_sublabel_macro(action_bind_sublabel_run_ahead_secondary_instance,  MENU_ENUM_SUBLABEL_RUN_AHEAD_SECONDARY_INSTANCE)
+default_sublabel_macro(action_bind_sublabel_run_ahead_frames,              MENU_ENUM_SUBLABEL_RUN_AHEAD_FRAMES)
 default_sublabel_macro(action_bind_sublabel_rewind,                        MENU_ENUM_SUBLABEL_REWIND_ENABLE)
 default_sublabel_macro(action_bind_sublabel_rewind_granularity,            MENU_ENUM_SUBLABEL_REWIND_GRANULARITY)
 default_sublabel_macro(action_bind_sublabel_libretro_log_level,            MENU_ENUM_SUBLABEL_LIBRETRO_LOG_LEVEL)
@@ -1109,6 +1112,15 @@ int menu_cbs_init_bind_sublabel(menu_file_list_cbs_t *cbs,
          case MENU_ENUM_LABEL_SLOWMOTION_RATIO:
             BIND_ACTION_SUBLABEL(cbs, action_bind_sublabel_slowmotion_ratio);
             break;
+         case MENU_ENUM_LABEL_RUN_AHEAD_ENABLED:
+            BIND_ACTION_SUBLABEL(cbs, action_bind_sublabel_run_ahead_enabled);
+            break;
+         case MENU_ENUM_LABEL_RUN_AHEAD_SECONDARY_INSTANCE:
+            BIND_ACTION_SUBLABEL(cbs, action_bind_sublabel_run_ahead_secondary_instance);
+            break;
+         case MENU_ENUM_LABEL_RUN_AHEAD_FRAMES:
+            BIND_ACTION_SUBLABEL(cbs, action_bind_sublabel_run_ahead_frames);
+            break;
          case MENU_ENUM_LABEL_FASTFORWARD_RATIO:
             BIND_ACTION_SUBLABEL(cbs, action_bind_sublabel_fastforward_ratio);
             break;

menu/menu_displaylist.c

@@ -4963,6 +4963,15 @@ bool menu_displaylist_ctl(enum menu_displaylist_ctl_state type, void *data)
          menu_displaylist_parse_settings_enum(menu, info,
                MENU_ENUM_LABEL_SLOWMOTION_RATIO,
                PARSE_ONLY_FLOAT, false);
+         menu_displaylist_parse_settings_enum(menu, info,
+            MENU_ENUM_LABEL_RUN_AHEAD_ENABLED,
+            PARSE_ONLY_BOOL, false);
+         menu_displaylist_parse_settings_enum(menu, info,
+            MENU_ENUM_LABEL_RUN_AHEAD_FRAMES,
+            PARSE_ONLY_UINT, false);
+         menu_displaylist_parse_settings_enum(menu, info,
+            MENU_ENUM_LABEL_RUN_AHEAD_SECONDARY_INSTANCE,
+            PARSE_ONLY_BOOL, false);
          if (settings->bools.menu_show_advanced_settings)
             menu_displaylist_parse_settings_enum(menu, info,
                   MENU_ENUM_LABEL_MENU_THROTTLE_FRAMERATE,