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libc/newlib/libc/machine/i960/strcmp_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 "strcm_ca.s"
#ifdef __PIC
.pic
#endif
#ifdef __PID
.pid
#endif
/*
* (c) copyright 1988,1993 Intel Corp., all rights reserved
*/
/*
procedure strcmp (optimized assembler version for the CA)
result = strcmp (src1_addr, src2_addr)
compare the null terminated string pointed to by src1_addr to
the string space pointed to by src2_addr. Return 0 iff the strings
are equal, -1 if src1_addr is lexicly less than src2_addr, and 1
if it is lexicly greater.
Undefined behavior will occur if the end of either 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, strcmp
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) source1 is word aligned, source2 is not
4) source2 is word aligned, source1 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 g14 are available
for use in this leafproc; other registers would have to be saved and
restored. These nine registers are sufficient to implement the routine.
The registers are used as follows:
g0 original src1 ptr; return result
g1 src2 ptr; 0xff -- byte extraction mask
g2 src1 word ptr
g3 src2 word ptr
Little endian:
g4 lsw of src1
g5 msw of src1
g6 src2 word
g7 extracted src1
Big endian:
g4 msw of src1
g5 lsw of src1
g6 extracted src1
g7 src2 word
g13 return address
g14 shift count
*/
#if __i960_BIG_ENDIAN__
#define MSW g4
#define LSW g5
#define SRC1 g6
#define SRC2 g7
#else
#define LSW g4
#define MSW g5
#define SRC2 g6
#define SRC1 g7
#endif
.globl _strcmp
.globl __strcmp
.leafproc _strcmp, __strcmp
.align 2
_strcmp:
#ifndef __PIC
lda Lrett,g14
#else
lda Lrett-(.+8)(ip),g14
#endif
__strcmp:
Lrestart:
notand g0,3,g2 # extract word addr of start of src1
lda (g14),g13 # preserve return address
#if __i960_BIG_ENDIAN__
cmpo g0,g2 # check alignment of src1
#endif
ld (g2),LSW # fetch word with at least first byte of src1
notand g1,3,g3 # extract word addr of start of src2
ld 4(g2),MSW # fetch second word of src1
#if __i960_BIG_ENDIAN__
bne Lsrc1_unaligned # branch if src1 is unaligned
cmpo g3,g1 # check alignment of src2
ld (g3),SRC2 # fetch word with at least first byte of src2
mov LSW,SRC1 # extract word of src1
lda 8(g2),g2 # advance src1 word addr
bne.f Lsrc2_unaligned # branch if src2 is NOT word aligned
/* src2 is word aligned */
Lwloop2: # word comparing loop
cmpo SRC2,SRC1 # compare src1 and src2 words
lda 0xff000000,g1 # byte extraction mask
mov MSW,LSW # move msw of src1 to lsw
ld (g2),MSW # pre-fetch next msw of src1
addo 4,g2,g2 # post-increment src1 addr
lda 4(g3),g3 # pre-increment src2 addr
bne.f Lcloop # branch if src1 and src2 unequal
scanbyte 0,SRC1 # check for null byte in src1 word
ld (g3),SRC2 # pre-fetch next word of src2
mov LSW,SRC1 # extract word of src1
lda 0,g0 # prepare to return zero, indicating equality
bno.t Lwloop2 # branch if null byte not encountered
/* words were equal and contained null byte */
mov 0,g14 # conform to register conventions
bx (g13) # return
Lsrc1_unaligned:
#endif
cmpo g3,g1 # check alignment of src2
ld (g3),SRC2 # fetch word with at least first byte of src2
shlo 3,g0,g14 # compute shift count for src1
#if __i960_BIG_ENDIAN__
subo g14,0,g14 # 32 - shift count for big endian.
#endif
eshro g14,g4,SRC1 # extract word of src1
lda 8(g2),g2 # advance src1 word addr
bne.f Lsrc2_unaligned # branch if src2 is NOT word aligned
/* at least src2 is word aligned */
Lwloop: # word comparing loop
cmpo SRC2,SRC1 # compare src1 and src2 words
#if __i960_BIG_ENDIAN__
lda 0xff000000,g1 # byte extraction mask
#else
lda 0xff,g1 # byte extraction mask
#endif
mov MSW,LSW # move msw of src1 to lsw
ld (g2),MSW # pre-fetch next msw of src1
addo 4,g2,g2 # post-increment src1 addr
lda 4(g3),g3 # pre-increment src2 addr
bne.f Lcloop # branch if src1 and src2 unequal
scanbyte 0,SRC1 # check for null byte in src1 word
ld (g3),SRC2 # pre-fetch next word of src2
eshro g14,g4,SRC1 # extract word of src1
lda 0,g0 # prepare to return zero, indicating equality
bno.t Lwloop # branch if null byte not encountered
/* words were equal and contained null byte */
mov 0,g14 # conform to register conventions
bx (g13) # return
Lcloop_setup: # setup for coming from Lsrc2_unaligned
mov LSW,SRC1 # restore extracted src1 word
#if __i960_BIG_ENDIAN__
lda 0xff000000,g1 # byte extraction mask
#else
lda 0xff,g1 # byte extraction mask
#endif
Lcloop: # character comparing loop
and SRC2,g1,g3 # extract next char of src2
and SRC1,g1,g0 # extract next char of src1
cmpobne.f g0,g3,.diff # check for equality
cmpo 0,g0 # check for null byte
#if __i960_BIG_ENDIAN__
shro 8,g1,g1 # shift mask for next byte
#else
shlo 8,g1,g1 # shift mask for next byte
#endif
bne.t Lcloop # branch if null not reached
/* words are equal up thru null byte */
mov 0,g14
bx (g13) # g0 = 0 (src1 == src2)
Lrett:
ret
.diff:
mov 0,g14
bl Lless_than_exit
Lgreater_than_exit:
mov 1,g0
bx (g13) # g0 = 1 (src1 > src2)
Lless_than_exit:
subi 1,0,g0
bx (g13) # g0 = -1 (src1 < src2)
Lsrc2_unaligned:
mov SRC1,LSW # retain src1 extracted word
ld 4(g3),SRC1 # fetch second word of src2
shlo 3,g1,MSW # compute shift count for src2
#if __i960_BIG_ENDIAN__
subo MSW,0,MSW # 32 - shift count for big endian.
#endif
eshro MSW,g6,SRC2 # extract word of src2
cmpo LSW,SRC2 # compare src1 and src2 words
notor g1,3,MSW # first step in computing new src1 ptr
lda 4(g3),g1 # set new src2 ptr
bne.f Lcloop_setup # first four bytes differ
scanbyte 0,LSW # check for null byte
lda (g13),g14 # prepare return pointer for Lrestart
subo MSW,g0,g0 # second (final) step in computing new src1 ptr
bno.t Lrestart # if null byte not encountered, continue
/* with both string fetches shifted such that */
/* src2 is now word aligned. */
mov 0,g14 # conform to register conventions.
lda 0,g0 # return indicator of equality.
bx (g13)
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