From 5338b62b86f0158176ace6f0f96bc5796f6f17cd Mon Sep 17 00:00:00 2001
From: Andy Wingo <wingo@pobox.com>
Date: Sun, 1 Feb 2009 11:25:51 +0100
Subject: [PATCH] don't make intermediate garbage when making vectors in the vm

* libguile/vm-i-system.c (vector): Don't cons up a list just to make a
  vector. Saves a couple percent in total cell allocation when loading
  syncase. Probably not worth it, but foo!
---
 libguile/vm-i-system.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/libguile/vm-i-system.c b/libguile/vm-i-system.c
index 179b6380a..002b0042e 100644
--- a/libguile/vm-i-system.c
+++ b/libguile/vm-i-system.c
@@ -160,9 +160,16 @@ VM_DEFINE_INSTRUCTION (16, vector, "vector", 2, -1, 1)
   unsigned h = FETCH ();
   unsigned l = FETCH ();
   unsigned len = ((h << 8) + l);
-  POP_LIST (len);
+  SCM vect;
+  
   SYNC_REGISTER ();
-  *sp = scm_vector (*sp);
+  sp++; sp -= len;
+  CHECK_UNDERFLOW ();
+  vect = scm_make_vector (scm_from_uint (len), SCM_BOOL_F);
+  memcpy (SCM_I_VECTOR_WELTS(vect), sp, sizeof(SCM) * len);
+  NULLSTACK (len);
+  *sp = vect;
+
   NEXT;
 }