--- gforth/comp-i.fs	2002/12/27 17:19:33	1.10
+++ gforth/comp-i.fs	2012/12/31 15:25:17	1.27
@@ -1,12 +1,12 @@
 \ Compare nonrelocatable images and produce a relocatable image
 
-\ Copyright (C) 1996,1997,1998 Free Software Foundation, Inc.
+\ Copyright (C) 1996,1997,1998,2002,2003,2004,2007,2010,2012 Free Software Foundation, Inc.
 
 \ This file is part of Gforth.
 
 \ Gforth is free software; you can redistribute it and/or
 \ modify it under the terms of the GNU General Public License
-\ as published by the Free Software Foundation; either version 2
+\ as published by the Free Software Foundation, either version 3
 \ of the License, or (at your option) any later version.
 
 \ This program is distributed in the hope that it will be useful,
@@ -15,19 +15,15 @@
 \ GNU General Public License for more details.
 
 \ You should have received a copy of the GNU General Public License
-\ along with this program; if not, write to the Free Software
-\ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
+\ along with this program. If not, see http://www.gnu.org/licenses/.
 
 s" address-unit-bits" environment? drop constant bits/au
-6 constant dodoes-tag
+7 constant dodoes-tag
 
 : write-cell { w^ w  file-id -- ior }
     \ write a cell to the file
     w cell file-id write-file ;
 
-: th ( addr1 n -- addr2 )
-    cells + ;
-
 : bset ( bmask c-addr -- )
     tuck c@ or swap c! ; 
 
@@ -43,12 +39,19 @@ s" address-unit-bits" environment? drop
     if
 	." : images have the same base address; producing only a data-relocatable image" cr
     else
-	offset abs expected-offset <> abort" images produced by different engines"
+	\ the following sanity check produces false positices with exec-shield
+	\ offset abs expected-offset <> abort" images produced by different engines"
 	."  offset=" offset . cr
 	0 image1 i-field + ! 0 image2 i-field + !
     endif
     base offset ;
-    
+
+: >tag ( index -- tag )
+    dup dodoes-tag 2 + > IF
+	$21 1 DO  dup tag-offsets I cells + @ < IF
+		tag-offsets I 1- cells + @ - I 1- 9 lshift + negate
+		UNLOOP  EXIT  THEN  LOOP
+    THEN  -2 swap - ;
 
 : compare-images { image1 image2 reloc-bits size file-id -- }
     \G compares image1 and image2 (of size cells) and sets reloc-bits.
@@ -59,7 +62,7 @@ s" address-unit-bits" environment? drop
     doffset 0= abort" images have the same dictionary base address"
     ." data offset=" doffset . cr
     ." code" image1 image2 cell     26 cells image-data { cbase coffset }
-    ."   xt" image1 image2 11 cells 22 cells image-data { xbase xoffset }
+    ."   xt" image1 image2 13 cells 22 cells image-data { xbase xoffset }
     size 0
     u+do
 	image1 i th @ image2 i th @ { cell1 cell2 }
@@ -70,28 +73,14 @@ s" address-unit-bits" environment? drop
 	else
 	    coffset 0<> cell1 coffset + cell2 = and
 	    if
-		cell1 cbase - cell / { tag }
-		tag dodoes-tag =
-		if
-		    \ make sure that the next cell will not be tagged
-		    \ !! can probably be optimized away with hybrid threading
-		    dbase negate image1 i 1+ th +!
-		    dbase doffset + negate image2 i 1+ th +!
-		endif
-		-2 tag $4000 or - file-id write-cell throw
+		cell1 cbase - cell/ { tag }
+		tag >tag $4000 xor file-id write-cell throw
 		i reloc-bits set-bit
 	    else
 		xoffset 0<> cell1 xoffset + cell2 = and
 		if
-		    cell1 xbase - cell / { tag }
-		    tag dodoes-tag =
-		    if
-			\ make sure that the next cell will not be tagged
-			\ !! can probably be optimized away with hybrid threading
-			dbase negate image1 i 1+ th +!
-			dbase doffset + negate image2 i 1+ th +!
-		    endif
-		    -2 tag - file-id write-cell throw
+		    cell1 xbase - cell/ { tag }
+		    tag >tag file-id write-cell throw
 		    i reloc-bits set-bit
 		else
 		    cell1 file-id write-cell throw
@@ -106,20 +95,20 @@ s" address-unit-bits" environment? drop
 
 : comp-image ( "image-file1" "image-file2" "new-image" -- )
     name slurp-file { image1 size1 }
-    image1 size1 s" Gforth3" search 0= abort" not a Gforth image"
+    image1 size1 s" Gforth4" search 0= abort" not a Gforth image"
     drop 8 + image1 - { header-offset }
     size1 aligned size1 <> abort" unaligned image size"
     image1 header-offset + 2 cells + @ header-offset + size1 <> abort" header gives wrong size"
     name slurp-file { image2 size2 }
     size1 size2 <> abort" image sizes differ"
     name ( "new-image" ) w/o bin create-file throw { outfile }
-    size1 header-offset - 1- cell / bits/au / 1+ { reloc-size }
+    size1 header-offset - 1- cell/ bits/au / 1+ { reloc-size }
     reloc-size allocate throw { reloc-bits }
     reloc-bits reloc-size erase
     image1 header-offset outfile write-file throw
     base @ hex
     image1 header-offset +  image2 header-offset +  reloc-bits
-    size1 header-offset - aligned cell /  outfile  compare-images
+    size1 header-offset - aligned cell/  outfile  compare-images
     base !
     reloc-bits reloc-size outfile write-file throw
     outfile close-file throw ;