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#++
#
# Copyright (c) 1993 by
# Digital Equipment Corporation, Maynard, MA
#
# This software is furnished under a license and may be used and copied
# only in accordance with the terms of such license and with the
# inclusion of the above copyright notice. This software or any other
# copies thereof may not be provided or otherwise made available to any
# other person. No title to and ownership of the software is hereby
# transferred.
#
# The information in this software is subject to change without notice
# and should not be construed as a commitment by Digital Equipment
# Corporation.
#
# Digital assumes no responsibility for the use or reliability of its
# software on equipment which is not supplied by Digital.
#
# Facility:
#
# GEM/OTS - GEM compiler system support library
#
# Abstract:
#
# OTS character string support, Alpha version
#
# Authors:
#
# Kent Glossop
#
# void ots_translate(char *dst, long dstlen, char *src, char table[256]);
#
# Translates a string using a translation table. Handles overlap.
#
# Special conventions: No stack space, r16-r21 and r26-r28 ONLY,
# no linkage pointer required.
# (Warning: The auto-loader potentially takes some regs across
# the call if this is being used in a shared lib. environment.)
#
# Modification history:
#
# 006 13 Nov 1992 KDG Initial non-tailored assembly version,
# replacing BLISS -005
#
# 007 26 Jan 1993 KDG Add underscore
#--
#include "ots_defs.hs"
# r16 destination address
# r17 length
# r18 source address
# r19 table address
# r20,r21,r27,r28 scratch
# r26 return address
#
.globl _OtsStringTranslate .ent _OtsStringTranslate_OtsStringTranslate: .set noat .set noreorder .frame sp,0,r26
# sort out which case to use
addq r18, r17, r27 # get end address of source + 1 for overlap check
cmpult r18, r16, r28 # true if src at lower addr than dest (note trans to self is not a "slow" case)
cmpult r16, r27, r27 # true if dst starts before end of src
beq r17, done # don't touch memory if length=0
and r27, r28, r28 # does dst have bad overlap with src?
blbs r28, overlap # go handle poorly overlapping src/dst
# simple forward loop case (~16 cycles/byte EV4)
# (length is presumed to be at least 1)
subq r18, 1, r18 # one before the beginning of the source
subq r16, 1, r16 # one before the beginning of the destination
forward_loop: ldq_u r20, 1(r18) # load the qw containing the source
lda r18, 1(r18) # bump the source pointer
ldq_u r21, 1(r16) # load the qw containing the destination
lda r16, 1(r16) # bump the destination pointer
extbl r20 ,r18, r20 # get the byte to translate
addq r19, r20, r20 # get the address of the translation
ldq_u r27, (r20) # load the translation
subq r17, 1, r17 # decrement length
mskbl r21, r16, r21 # clear the bits in the destination
extbl r27, r20, r27 # extract the translation
insbl r27, r16, r27 # position for insertion
bis r27, r21, r21 # merge into the destination
stq_u r21, (r16) # store back
bgt r17, forward_loop # do another if there
done: ret r31, (r26) nop #.align 3
# bad overlap case (~16 cycles/byte EV4, 11c/byte EV5)
# (length is presumed to be at least 1)
overlap: addq r17, r18, r18 # one past the end of the source
addq r17, r16, r16 # one past the end of the destination
backward_loop: ldq_u r20, -1(r18) # load the qw containing the source
lda r18, -1(r18) # bump the source pointer
ldq_u r21, -1(r16) # load the qw containing the destination
lda r16, -1(r16) # bump the destination pointer
extbl r20 ,r18, r20 # get the byte to translate
addq r19, r20, r20 # get the address of the translation
ldq_u r27, (r20) # load the translation
subq r17, 1, r17 # decrement length
mskbl r21, r16, r21 # clear the bits in the destination
extbl r27, r20, r27 # extract the translation
insbl r27, r16, r27 # position for insertion
bis r27, r21, r21 # merge into the destination
stq_u r21, (r16) # store back
bgt r17, backward_loop # do another if there
ret r31, (r26)
.set at .set reorder .end _OtsStringTranslate
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