From 7b29ef15529f6850ba5710bee0c2b672b69c4f7b Mon Sep 17 00:00:00 2001
From: vsc <vsc@b08c6af1-5177-4d33-ba66-4b1c6b8b522a>
Date: Fri, 29 Sep 2006 18:59:00 +0000
Subject: [PATCH] avoid doing full stack shifting when on top of stack.

git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@1699 b08c6af1-5177-4d33-ba66-4b1c6b8b522a
---
 C/globals.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/C/globals.c b/C/globals.c
index 30843296d..0e4f7dd4a 100644
--- a/C/globals.c
+++ b/C/globals.c
@@ -265,8 +265,10 @@ GrowArena(Term arena, CELL *pt, UInt old_size, UInt size, UInt arity)
   if (size < 4096) {
     size = 4096;
   }
-  if (pt == H && ArenaPt(arena) >= B->cp_h) {
+  if (pt == H) {
+    choiceptr b_ptr;
     if (H+size > ASP-1024) {
+
       XREGS[arity+1] = arena;
       if (!Yap_gcl(size*sizeof(CELL), arity+1, ENV, P)) {
 	Yap_Error(OUT_OF_STACK_ERROR, TermNil, Yap_ErrorMessage);
@@ -274,6 +276,12 @@ GrowArena(Term arena, CELL *pt, UInt old_size, UInt size, UInt arity)
       }
       arena = XREGS[arity+1];
     }
+    /* adjust possible back pointers in choice-point stack */
+    b_ptr = B;
+    while (b_ptr->cp_h == H) {
+      b_ptr->cp_h += size;
+      b_ptr = b_ptr->cp_b;
+    }
     H += size;
   } else {
     XREGS[arity+1] = arena;