From 22e57a8eabe1da6065da5217545cd8b240ac6a16 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Petri=20H=C3=A4kkinen?= <petrih@rmd.remedy.fi>
Date: Tue, 24 May 2022 09:55:41 +0300
Subject: [PATCH] Optimize lua_touserdata by checking userdata case first

---
 VM/src/lapi.cpp | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/VM/src/lapi.cpp b/VM/src/lapi.cpp
index 4893f78a..df144a15 100644
--- a/VM/src/lapi.cpp
+++ b/VM/src/lapi.cpp
@@ -487,15 +487,13 @@ void* lua_tolightuserdata(lua_State* L, int idx)
 void* lua_touserdata(lua_State* L, int idx)
 {
     StkId o = index2addr(L, idx);
-    switch (ttype(o))
-    {
-    case LUA_TUSERDATA:
+    // fast-path: check userdata first since it is most likely the expected result
+    if (ttisuserdata(o))
         return uvalue(o)->data;
-    case LUA_TLIGHTUSERDATA:
+    else if (ttislightuserdata(o))
         return pvalue(o);
-    default:
+    else
         return NULL;
-    }
 }
 
 void* lua_touserdatatagged(lua_State* L, int idx, int tag)