From 9bf7babb9a54307743e29954a5c922d30f438f79 Mon Sep 17 00:00:00 2001
From: gendlin <108626604+gendlin@users.noreply.github.com>
Date: Tue, 4 Jun 2024 09:19:32 -0400
Subject: [PATCH] Improve frame limiter behavior on older CPUs (#1723)

---
 src/i_video.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/src/i_video.c b/src/i_video.c
index 8e448bb2..9256b56f 100644
--- a/src/i_video.c
+++ b/src/i_video.c
@@ -714,6 +714,17 @@ static unsigned int disk_to_draw, disk_to_restore;
 static void CreateUpscaledTexture(boolean force);
 static void I_ResetTargetRefresh(void);
 
+//
+// I_CpuPause
+//  Avoids a performance penalty on exit from busy-wait loops. This should be
+//  called on every iteration of the loop and positioned near the loop exit.
+//
+#if SDL_VERSION_ATLEAST(2, 24, 0)
+ #define I_CpuPause() SDL_CPUPauseInstruction()
+#else
+ #define I_CpuPause()
+#endif
+
 void I_FinishUpdate(void)
 {
     if (noblit)
@@ -787,6 +798,8 @@ void I_FinishUpdate(void)
             uint64_t elapsed_time = current_time - frametime_start;
             uint64_t remaining_time = 0;
 
+            I_CpuPause();
+
             if (elapsed_time >= target_time)
             {
                 frametime_start = current_time;