core_run: skip game_ai_think when no override or debug is active

The HAVE_GAME_AI block in core_run called game_ai_think on every frame
regardless of whether any GameAI feature was actually requested. The
function itself always runs game_ai_lib_set_show_debug(ga, show_debug)
when an AI instance has been created (line 172 of ai/game_ai.c), which
is an indirect dispatch into the loaded GameAI library and runs even
when override_p1, override_p2, and show_debug are all false.

When the user has loaded a GameAI library but is not currently using
any of its overrides, this per-frame dispatch is wasted work.

Gate the call in core_run on at least one of the three settings being
active. When all are false:
  - The function call is skipped (function-call overhead saved)
  - The per-frame game_ai_lib_set_show_debug dispatch is skipped
    (the meaningful win when an AI lib is loaded but unused)
  - The internal g_frameCount counter doesn't tick, so when overrides
    eventually flip on, the first think() may fire on the very next
    frame rather than after the SKIPFRAMES delay. Harmless - the user
    just enabled the feature; immediate AI input is the desired UX.
  - The lazy 'ga' creation path inside game_ai_think (gated on
    !ga && g_ram_ptr) is deferred until overrides actually turn on,
    which is correct: no point creating an AI instance for a frame
    that won't use it.

For builds without HAVE_GAME_AI, the entire block is removed by the
preprocessor and this change has no effect.

For builds with HAVE_GAME_AI but no GameAI library ever loaded, the
work skipped by the new gate is sub-microsecond per frame. For builds
with a GameAI library loaded but overrides currently off, the skip
avoids one per-frame indirect function-pointer dispatch into the
loaded shared library, which is a real per-frame win measured in
hundreds of cycles depending on the AI lib's implementation.

Author: LibretroAdmin

runloop.c

@@ -8267,16 +8267,27 @@ void core_run(void)
 #ifdef HAVE_GAME_AI
    {
       settings_t *settings           = config_get_ptr();
-      video_driver_state_t *video_st = video_state_get_ptr();
-      game_ai_think(
-            settings->bools.game_ai_override_p1,
-            settings->bools.game_ai_override_p2,
-            settings->bools.game_ai_show_debug,
-            video_st->frame_cache_data,
-            video_st->frame_cache_width,
-            video_st->frame_cache_height,
-            video_st->frame_cache_pitch,
-            video_st->pix_fmt);
+      bool override_p1               = settings->bools.game_ai_override_p1;
+      bool override_p2               = settings->bools.game_ai_override_p2;
+      bool show_debug                = settings->bools.game_ai_show_debug;
+
+      /* Skip the call entirely when no GameAI feature is active for this
+       * frame. Avoids per-frame indirect dispatch into the loaded GameAI
+       * library (game_ai_lib_set_show_debug) that game_ai_think runs
+       * unconditionally when an AI has been instantiated. */
+      if (override_p1 || override_p2 || show_debug)
+      {
+         video_driver_state_t *video_st = video_state_get_ptr();
+         game_ai_think(
+               override_p1,
+               override_p2,
+               show_debug,
+               video_st->frame_cache_data,
+               video_st->frame_cache_width,
+               video_st->frame_cache_height,
+               video_st->frame_cache_pitch,
+               video_st->pix_fmt);
+      }
    }
 #endif