From b794404333d44c419e08de40650316bac07e943c Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Tue, 22 Dec 2015 14:33:39 -0700
Subject: [PATCH] faster path for a procedure impersonator w/o wrapper proc

Make the call path faster when an impersontor is present
on a procedure only to add impersonator properties.
---
 racket/src/racket/src/schnapp.inc | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/racket/src/racket/src/schnapp.inc b/racket/src/racket/src/schnapp.inc
index a3d585406d..c0d1e7f26e 100644
--- a/racket/src/racket/src/schnapp.inc
+++ b/racket/src/racket/src/schnapp.inc
@@ -60,12 +60,19 @@ Scheme_Object *PRIM_APPLY_NAME(Scheme_Object *rator,
 
     t = _SCHEME_TYPE(rator);
 
+    if ((t == scheme_proc_chaperone_type)
+        && SCHEME_VECTORP(((Scheme_Chaperone *)rator)->redirects)
+        && (SCHEME_VEC_SIZE(((Scheme_Chaperone *)rator)->redirects) & 0x1)) {
+      if (SCHEME_FALSEP(SCHEME_VEC_ELS(((Scheme_Chaperone *)rator)->redirects)[0])) {
+        /* No redirection proc (i.e, chaperone is just for properties) */
+        rator = ((Scheme_Chaperone *)rator)->prev;
+        t = _SCHEME_TYPE(rator);
+      } else
+        return scheme_apply_chaperone(rator, argc, argv, NULL, PRIM_CHECK_MULTI | (PRIM_CHECK_VALUE << 1));
+    }
+
     if (t == scheme_prim_type) {
       return PRIM_APPLY_NAME_FAST(rator, argc, argv);
-    } else if ((t == scheme_proc_chaperone_type)
-               && SCHEME_VECTORP(((Scheme_Chaperone *)rator)->redirects)
-               && (SCHEME_VEC_SIZE(((Scheme_Chaperone *)rator)->redirects) & 0x1)) {
-      return scheme_apply_chaperone(rator, argc, argv, NULL, PRIM_CHECK_MULTI | (PRIM_CHECK_VALUE << 1));
     }
   }