From 248c175609b435fb3a3ebdcc1f7a2c17d9bd77fd Mon Sep 17 00:00:00 2001
From: Tatsuya79
Date: Thu, 8 Feb 2018 13:02:18 +0100
Subject: Overclock by reducing cycles.

---
 libretro/libretro.c | 31 +++++++++++++++++++++++++++++++
 src/snes9x.h        |  8 +++++---
 2 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/libretro/libretro.c b/libretro/libretro.c
index b7d371c..959d2e6 100644
--- a/libretro/libretro.c
+++ b/libretro/libretro.c
@@ -91,6 +91,7 @@ static uint32 joys[5];
 
 bool8 ROMAPUEnabled = 0;
 char currentWorkingDir[MAX_PATH+1] = {0};
+bool overclock_cycles = false;
 
 memstream_t *s_stream;
 
@@ -351,10 +352,17 @@ static void snes_init (void)
 
 void retro_init (void)
 {
+   static const struct retro_variable vars[] =
+   {
+      { "snes9x2002_overclock_cycles", "CPU Overclock (Hack, Unsafe, Restart); disabled|enabled" },
+      { NULL, NULL },
+   };
+
    if (!environ_cb(RETRO_ENVIRONMENT_GET_OVERSCAN, &use_overscan))
 	   use_overscan = FALSE;
 
    snes_init();
+   environ_cb(RETRO_ENVIRONMENT_SET_VARIABLES, (void*)vars);
 }
 
 /* libsnes uses relative values for analogue devices. 
@@ -414,10 +422,31 @@ static void report_buttons (void)
 	}
 }
 
+static void check_variables(void)
+{
+   struct retro_variable var;
+
+   var.key = "snes9x2002_overclock_cycles";
+   var.value = NULL;
+
+   if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var) && var.value)
+      {
+        if (strcmp(var.value, "enabled") == 0)
+          overclock_cycles = true;
+        else
+          overclock_cycles = false;
+      }
+}
+
 //#define FRAME_SKIP
 
 void retro_run (void)
 {
+   bool updated = false;
+
+   if (environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE_UPDATE, &updated) && updated)
+      check_variables();
+
 #ifdef FRAME_SKIP
    IPPU.RenderThisFrame = !IPPU.RenderThisFrame;
 #else
@@ -517,6 +546,8 @@ bool retro_load_game(const struct retro_game_info *game)
    bool8 loaded;
    enum retro_pixel_format fmt = RETRO_PIXEL_FORMAT_RGB565;
 
+   check_variables();
+
    if (!environ_cb(RETRO_ENVIRONMENT_SET_PIXEL_FORMAT, &fmt))
    {
       fprintf(stderr, "[libretro]: RGB565 is not supported.\n");
diff --git a/src/snes9x.h b/src/snes9x.h
index d7dd7ef..065b98d 100644
--- a/src/snes9x.h
+++ b/src/snes9x.h
@@ -133,6 +133,8 @@ enum
    SNES_MAX_CONTROLLER_OPTIONS
 };
 
+extern bool overclock_cycles;
+
 #define DEBUG_MODE_FLAG     (1 << 0)
 #define TRACE_FLAG         (1 << 1)
 #define SINGLE_STEP_FLAG    (1 << 2)
@@ -147,9 +149,9 @@ enum
 #define IRQ_PENDING_FLAG    (1 << 11)
 
 #ifdef VAR_CYCLES
-#define ONE_CYCLE 6
-#define SLOW_ONE_CYCLE 8
-#define TWO_CYCLES 12
+#define ONE_CYCLE (overclock_cycles ? 4 : 6)
+#define SLOW_ONE_CYCLE (overclock_cycles ? 4 : 8)
+#define TWO_CYCLES (overclock_cycles ? 6 : 12)
 #else
 #define ONE_CYCLE 1
 #define SLOW_ONE_CYCLE 1
-- 
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