From f13c269b7ffde245f12503fc9c80f92fcea2026a Mon Sep 17 00:00:00 2001
From: Andy Wingo <wingo@pobox.com>
Date: Sat, 13 Sep 2008 14:30:57 +0200
Subject: [PATCH] inline FREE_FRAME in return, sync stack_base in
 CACHE_REGISTER

* libguile/vm-engine.h (CACHE_REGISTER): Sync stack_base too.

* libguile/vm-i-system.c (return): Inline FREE_FRAME here,
  micro-optimizing a wee bit. Sounds silly, but it's to enable some
  refactoring.
---
 libguile/vm-engine.h   |  1 +
 libguile/vm-i-system.c | 22 +++++++++++++++++++++-
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/libguile/vm-engine.h b/libguile/vm-engine.h
index 370a42b15..c86307c86 100644
--- a/libguile/vm-engine.h
+++ b/libguile/vm-engine.h
@@ -132,6 +132,7 @@
   ip = vp->ip;					\
   sp = vp->sp;					\
   fp = vp->fp;					\
+  stack_base = fp ? SCM_FRAME_UPPER_ADDRESS (fp) - 1 : vp->stack_base; \
 }
 
 #define SYNC_REGISTER()				\
diff --git a/libguile/vm-i-system.c b/libguile/vm-i-system.c
index 546891169..aff8331e9 100644
--- a/libguile/vm-i-system.c
+++ b/libguile/vm-i-system.c
@@ -670,7 +670,27 @@ VM_DEFINE_INSTRUCTION (return, "return", 0, 0, 1)
  vm_return:
   EXIT_HOOK ();
   RETURN_HOOK ();
-  FREE_FRAME ();
+  {
+    SCM ret, *data;
+    data = SCM_FRAME_DATA_ADDRESS (fp);
+
+    POP (ret);
+#ifdef THE_GOVERNMENT_IS_AFTER_ME
+    if (sp != stack_base)
+      abort ();
+    if (stack_base != data + 3)
+      abort ();
+#endif
+
+    /* Restore registers */
+    sp = SCM_FRAME_LOWER_ADDRESS (fp);
+    ip = SCM_FRAME_BYTE_CAST (data[3]);
+    fp = SCM_FRAME_STACK_CAST (data[2]);
+    stack_base = SCM_FRAME_UPPER_ADDRESS (fp) - 1;
+
+    /* Set return value (sp is already pushed) */
+    *sp = ret;
+  }
 
   /* Restore the last program */
   program = SCM_FRAME_PROGRAM (fp);