Retro68/gcc/newlib/libc/machine/i960/strncpy_ca.S

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/*******************************************************************************
*
* Copyright (c) 1993 Intel Corporation
*
* Intel hereby grants you permission to copy, modify, and distribute this
* software and its documentation. Intel grants this permission provided
* that the above copyright notice appears in all copies and that both the
* copyright notice and this permission notice appear in supporting
* documentation. In addition, Intel grants this permission provided that
* you prominently mark as "not part of the original" any modifications
* made to this software or documentation, and that the name of Intel
* Corporation not be used in advertising or publicity pertaining to
* distribution of the software or the documentation without specific,
* written prior permission.
*
* Intel Corporation provides this AS IS, WITHOUT ANY WARRANTY, EXPRESS OR
* IMPLIED, INCLUDING, WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY
* OR FITNESS FOR A PARTICULAR PURPOSE. Intel makes no guarantee or
* representations regarding the use of, or the results of the use of,
* the software and documentation in terms of correctness, accuracy,
* reliability, currentness, or otherwise; and you rely on the software,
* documentation and results solely at your own risk.
*
* IN NO EVENT SHALL INTEL BE LIABLE FOR ANY LOSS OF USE, LOSS OF BUSINESS,
* LOSS OF PROFITS, INDIRECT, INCIDENTAL, SPECIAL OR CONSEQUENTIAL DAMAGES
* OF ANY KIND. IN NO EVENT SHALL INTEL'S TOTAL LIABILITY EXCEED THE SUM
* PAID TO INTEL FOR THE PRODUCT LICENSED HEREUNDER.
*
******************************************************************************/
.file "sncpy_ca.s"
#ifdef __PIC
.pic
#endif
#ifdef __PID
.pid
#endif
/*
* (c) copyright 1988,1993 Intel Corp., all rights reserved
*/
/*
procedure strncpy (optimized assembler version for the CA)
dest_addr = strncpy (dest_addr, src_addr, max_bytes)
copy the null terminated string pointed to by src_addr to
the string space pointed to by dest_addr. Return the original
dest_addr. If the source string is shorter than max_bytes,
then null-pad the destination string.
This routine will fail if the source and destination string
overlap (in particular, if the end of the source is overlapped
by the beginning of the destination). The behavior is undefined.
This is acceptable according to the draft C standard.
Undefined behavior will also occur if the end of the source string
(i.e. the terminating null byte) is in the last word of the program's
allocated memory space. This is so because, in several cases, strcpy
will fetch ahead one word. Disallowing the fetch ahead would impose
a severe performance penalty.
This program handles five cases:
1) both arguments start on a word boundary
2) neither are word aligned, but they are offset by the same amount
3) source is word aligned, destination is not
4) destination is word aligned, source is not
5) neither is word aligned, and they are offset by differing amounts
At the time of this writing, only g0 thru g7 and g13 are available
for use in this leafproc; other registers would have to be saved and
restored. These nine registers, plus tricky use of g14 are sufficient
to implement the routine. The registers are used as follows:
g0 original dest ptr; not modified, so that it may be returned.
g1 src ptr; shift count
g2 max_bytes
g3 src ptr (word aligned)
g4 dest ptr (word aligned)
g5 0xff -- byte extraction mask
Little endian:
g6 lsw of double word for extraction of 4 bytes
g7 msw of double word for extraction of 4 bytes
Big endian:
g6 msw of double word for extraction of 4 bytes
g7 lsw of double word for extraction of 4 bytes
g13 return address
g14 byte extracted.
*/
#if __i960_BIG_ENDIAN__
#define MSW g6
#define LSW g7
#else
#define LSW g6
#define MSW g7
#endif
.globl _strncpy
.globl __strncpy
.leafproc _strncpy, __strncpy
.align 2
_strncpy:
#ifndef __PIC
lda Lrett,g14
#else
lda Lrett-(.+8)(ip),g14
#endif
__strncpy:
notand g1,3,g3 # extract word addr of start of src
lda (g14),g13 # preserve return address
cmpibge.f 0,g2,Lexit_code # Lexit if number of bytes to move is <= zero.
cmpo g3,g1 # check alignment of src
ld (g3),LSW # fetch word containing at least first byte
notand g0,3,g4 # extract word addr of start of dest
lda 4(g3),g3 # advance src word addr
bne.f Lcase_245 # branch if src is NOT word aligned
Lcase_13:
cmpo g0,g4 # check alignment of dest
lda 0xff,g5 # load mask for byte extraction
subo 4,g4,g4 # store is pre-incrementing; back up dest addr
bne.f Lcase_3 # branch if dest not word aligned
Lcase_1: # src and dest are word aligned
Lcase_1_wloop: # word copying loop
cmpi g2,4 # check for fewer than four bytes to move
lda (LSW),g1 # keep a copy of the src word
addo 4,g4,g4 # pre-increment dest addr
bl.f Lcase_1_cloop.a # branch if fewer than four bytes to copy
scanbyte 0,g1 # check for null byte in src word
ld (g3),LSW # pre-fetch next word of src
subi 4,g2,g2 # decrease max_byte count by the 4 bytes moved
bo.f Lcase_1_cloop.c # branch if word contains null byte
addo 4,g3,g3 # post-increment src addr
st g1,(g4) # store word in dest string
b Lcase_1_wloop
Lcase_3_cloop.a:
Lcase_1_cloop.a: # character copying loop (max_bytes <= 3)
#if __i960_BIG_ENDIAN__
rotate 8,g1,g1 # move next byte into position for extraction
#endif
and g5,g1,g14 # extract next char
Lcase_1_cloop.b:
cmpdeci 0,g2,g2 # is max_bytes exhausted?
be.f Lexit_code # Lexit if max_bytes is exhausted
cmpo 0,g14 # check for null byte
stob g14,(g4) # store the byte in dest
#if ! __i960_BIG_ENDIAN__
shro 8,g1,g1 # move next byte into position for extraction
#endif
lda 1(g4),g4 # post-increment dest byte addr
bne.t Lcase_1_cloop.a # branch if null not reached
b Lcase_1_cloop.b
Lexit_code:
mov 0,g14 # conform to register conventions
bx (g13) # g0 = addr of dest; g14 = 0
Lrett:
ret
Lcase_1_cloop.c:
Lcase_3_cloop.c:
#if __i960_BIG_ENDIAN__
rotate 24,g5,g5 # move mask into position for testing next byte
#endif
and g5,g1,g14 # extract next char
cmpo 0,g14 # check for null byte
#if ! __i960_BIG_ENDIAN__
lda (g5),LSW # keep a copy of the current mask
shlo 8,g5,g5 # move mask into position for testing next byte
#endif
bne.t Lcase_1_cloop.c # branch if null not reached
#if __i960_BIG_ENDIAN__
subo 1,g5,g5 # null pad.
andnot g5,g1,g1 # last bytes to copy, and null pad rest of word
#else
subo 1,LSW,g5 # mask to get last bytes to copy, and null pad
and g5,g1,g1 # last bytes to copy, and null pad rest of word
#endif
st g1,(g4)
Lcase_1_zwloop: # zero word loop
cmpi g2,4 # check for fewer than four bytes to move
addo 4,g4,g4 # pre-increment dest addr
bl.f Lcase_1_cloop.b # branch if fewer than four bytes to copy
subo 4,g2,g2 # decrease max_byte count by the 4 bytes moved
st g14,(g4) # store word in dest string
b Lcase_1_zwloop
Lcase_3: # src is word aligned; dest is not
addo 8,g4,g4 # move dest word ptr to first word boundary
lda (g0),g1 # copy dest byte ptr
mov LSW,MSW # make copy of first word of src
lda 32,g14 # initialize shift count to zero (mod 32)
Lcase_25:
Lcase_3_cloop_at_start: # character copying loop for start of dest str
cmpdeci 0,g2,g2 # is max_bytes exhausted?
#if __i960_BIG_ENDIAN__
shro 24,MSW,g5 # extract next char
#else
and g5,MSW,g5 # extract next char
#endif
be.f Lexit_code # Lexit if max_bytes is exhausted
cmpo 0,g5 # check for null byte
stob g5,(g1) # store the byte in dest
addo 1,g1,g1 # post-increment dest ptr
lda 0xff,g5 # re-initialize byte extraction mask
bne.t 1f # drop thru if null byte reached (to pad)
movl 0,g6 # blank out remainder of input buffer
1:
cmpo g1,g4 # have we reached word boundary in dest yet?
#if __i960_BIG_ENDIAN__
lda -8(g14),g14 # augment the shift counter
rotate 8,MSW,MSW # move next byte into position for extraction
#else
lda 8(g14),g14 # augment the shift counter
shro 8,MSW,MSW # move next byte into position for extraction
#endif
bne.t Lcase_3_cloop_at_start # branch if reached word boundary?
ld (g3),MSW # fetch msw of operand for double shift
Lcase_4:
#if __i960_BIG_ENDIAN__
cmpobne 0,g14,Lcase_3_wloop # branch if src is still unaligned.
Lcase_3_wloop2:
cmpi g2,4 # less than four bytes to move?
lda (LSW),g1 # extract 4 bytes of src
lda 4(g3),g3 # post-increment src word addr
bl.f Lcase_3_cloop.a # branch if < four bytes left to move
scanbyte 0,g1 # check for null byte
lda (MSW),LSW # move msw to lsw
subi 4,g2,g2 # decrease max_byte count by the 4 bytes moved
ld (g3),MSW # pre-fetch msw of operand for double shift
bo.f Lcase_3_cloop.c # branch if word contains null byte
st g1,(g4) # store 4 bytes to dest
addo 4,g4,g4 # post-increment dest ptr
b Lcase_3_wloop2
#endif
Lcase_3_wloop:
cmpi g2,4 # less than four bytes to move?
eshro g14,g6,g1 # extract 4 bytes of src
lda 4(g3),g3 # post-increment src word addr
bl.f Lcase_3_cloop.a # branch if < four bytes left to move
scanbyte 0,g1 # check for null byte
lda (MSW),LSW # move msw to lsw
subi 4,g2,g2 # decrease max_byte count by the 4 bytes moved
ld (g3),MSW # pre-fetch msw of operand for double shift
bo.f Lcase_3_cloop.c # branch if word contains null byte
st g1,(g4) # store 4 bytes to dest
addo 4,g4,g4 # post-increment dest ptr
b Lcase_3_wloop
Lcase_245:
cmpo g0,g4 # check alignment of dest
ld (g3),MSW # pre-fetch second half
and 3,g1,g1 # compute shift count
lda 0xff,g5 # load mask for byte extraction
#if __i960_BIG_ENDIAN__
subo g1,4,g14 # adjust shift count for big endian.
shlo 3,g14,g14
#else
shlo 3,g1,g14
#endif
be.t Lcase_4 # branch if dest is word aligned
or g4,g1,g1 # is src earlier in word, later, or sync w/ dst
cmpo g0,g1 # < indicates first word of dest has more bytes
/* than first word of source. */
lda 4(g4),g4 # move dest word addr to first word boundary
eshro g14,g6,g5 # extract four bytes
lda (g0),g1
bg.f 1f
mov MSW,LSW
lda 4(g3),g3 # move src word addr to second word boundary
1:
mov g5,MSW
lda 0xff,g5
b Lcase_25
/* end of strncpy */