From 916c5705572d1be977dcb30db8b95c458932e453 Mon Sep 17 00:00:00 2001
From: Andy Wingo <wingo@pobox.com>
Date: Mon, 20 Aug 2018 12:45:07 +0200
Subject: [PATCH] Tweak to instrument-entry

* libguile/vm-engine.c (instrument-entry): Eagerly check if data->mcode
  is already set, and in that case just jump directly without checking
  the counter.
---
 libguile/vm-engine.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/libguile/vm-engine.c b/libguile/vm-engine.c
index e8787eeeb..c8db813a6 100644
--- a/libguile/vm-engine.c
+++ b/libguile/vm-engine.c
@@ -463,6 +463,14 @@ VM_NAME (scm_thread *thread)
 
       data = (struct scm_jit_function_data *) (ip + data_offset);
 
+      if (data->mcode)
+        {
+          SYNC_IP ();
+          scm_jit_enter_mcode (thread, data->mcode);
+          CACHE_REGISTER ();
+          NEXT (0);
+        }
+
       if (data->counter > SCM_JIT_COUNTER_THRESHOLD)
         {
           const uint8_t *mcode;