r1011 - cpu/x86

Author: wmb
Date: 2008-12-04 10:17:34 +0100 (Thu, 04 Dec 2008)
New Revision: 1011

Added:
   cpu/x86/occhksum.fth
Modified:
   cpu/x86/basefw.bth
Log:
Added fast IP checksum routine (x86 assembly language).

Modified: cpu/x86/basefw.bth
===================================================================
--- cpu/x86/basefw.bth	2008-12-04 09:17:30 UTC (rev 1010)
+++ cpu/x86/basefw.bth	2008-12-04 09:17:34 UTC (rev 1011)
@@ -23,6 +23,8 @@

\ fload ${BP}/forth/lib/showmsgs.fth	\ List error messages

+fload ${BP}/cpu/x86/occhksum.fth	\ IP checksum primitive
+
 fload ${BP}/ofw/core/ofwcore.fth	\ Device tree and other OBP routines
 [ifndef] no-tools
 fload ${BP}/ofw/core/ofwfw.fth		\ FirmWorks enhancements

Added: cpu/x86/occhksum.fth
===================================================================
--- cpu/x86/occhksum.fth	                        (rev 0)
+++ cpu/x86/occhksum.fth	2008-12-04 09:17:34 UTC (rev 1011)
@@ -0,0 +1,92 @@
+purpose: Internet checksum (one's complement of 16-bit words) primitive
+\ See license at end of file
+
+\ The complete checksum calculation consists of:
+\ a) add together all the 16-bit big-endian words in the buffer, with
+\    wrap-around carry (i.e. a carry out of the high bit is added back
+\    in at the low bit).
+\ b) Take the one's complement of the result, preserving only the
+\    least-significant 16 bits.
+\ c) If the result is 0, change it to ffff.
+
+\ The process of computing a checksum for UDP packets involves the
+\ creation of a "pseudo header" containing selected information
+\ from the IP header, and checksumming the combination of that pseudo
+\ header and the UDP packet.  To do so, it is convenient to perform
+\ step (a) of the calculation separately on the two pieces (pseudo header
+\ and UDP packet).  Thus we factor the checksum calculation code with
+\ a separate primitive "(oc-checksum)" that performs step (a).  That
+\ primitive is worth optimizing; steps (b) and (c) are typically not.
+
+headerless
+\ This computation depends on some properties of one's complement
+\ summation.  The computation can be done in either endianness,
+\ so we do it in little-endian, swapping at the end, to save time
+\ on x86.  We also do it 32 bits at a time, folding the result
+\ at the end.
+
+code (oc-checksum)  ( accum adr len -- checksum )
+   bx          pop     \ bx: len
+   ax          pop     \ ax: adr
+   dx          pop     \ dx: accum
+   si          push    \ save si
+   ax   si     mov     \ si: adr  ax: dead
+   bx   cx     mov     \ cx:len
+   2 #  cx     shr     \ cx:#shortwords
+
+   dl dh xchg  \ Byte swap into LE form
+   clc         \ Initial carry is 0
+   cx cx or  0<>  if
+      begin
+         ax lods
+         ax dx adc
+      loopa
+   then
+
+   0 # dx adc   \ Final carry
+
+   2 # bx test  0<>  if      \ Leftover short?
+      ax ax xor
+      op: ax lods
+      ax dx add
+      0 # dx adc  \ Possible carry 
+   then
+
+   1 # bx test  0<>  if      \ Leftover byte?
+      ax ax xor
+      al lodsb
+      ax dx add
+      0 # dx adc  \ Possible carry   
+   then
+
+   dx ax mov  d# 16 # ax shr  h# ffff # dx and  ax dx add  \ Add two halves
+   dx ax mov  d# 16 # ax shr  h# ffff # dx and  ax dx add  \ Again for carry
+   dl dh xchg   \ Byte swap   
+
+   si pop
+   dx push
+c;
+
+\ LICENSE_BEGIN
+\ Copyright (c) 2008 FirmWorks
+\ 
+\ Permission is hereby granted, free of charge, to any person obtaining
+\ a copy of this software and associated documentation files (the
+\ "Software"), to deal in the Software without restriction, including
+\ without limitation the rights to use, copy, modify, merge, publish,
+\ distribute, sublicense, and/or sell copies of the Software, and to
+\ permit persons to whom the Software is furnished to do so, subject to
+\ the following conditions:
+\ 
+\ The above copyright notice and this permission notice shall be
+\ included in all copies or substantial portions of the Software.
+\ 
+\ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+\ EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+\ MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+\ NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+\ LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+\ OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+\ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+\
+\ LICENSE_END