Subversion Repositories openrisc_2011-10-31

/*******************************************************************************

 *

 * 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 "sncmp_ca.s"

#ifdef  __PIC

        .pic

#endif

#ifdef  __PID

        .pid

#endif

/*

 * (c) copyright 1988,1993 Intel Corp., all rights reserved

 */

/*

        procedure strncmp  (optimized assembler version for the CA)

        result = strncmp (src1_addr, src2_addr, max_bytes)

        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.  Do not compare more than max_bytes bytes.

        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, strncmp

        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;  extracted word;  return result

        g1  src2 ptr;  0xff  --  byte extraction mask

        g2  maximum number of bytes to compare

        g3  src2 word ptr

        Little endian:

                g4  lsw of src1

                g5  msw of src1

                g6  src2 word

                g7  src1 word ptr

        Big endian:

                g4  msw of src1

                g5  lsw of src1

                g6  src1 word ptr

                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  _strncmp

        .globl  __strncmp

        .leafproc       _strncmp, __strncmp

        .align  2

_strncmp:

#ifndef __PIC

        lda     Lrett,g14

#else

        lda     Lrett-(.+8)(ip),g14

#endif

__strncmp:

Lrestart:

        notand  g0,3,SRC1       # extract word addr of start of src1

         lda    (g14),g13       # preserve return address

         cmpibge.f 0,g2,Lequal_exit     # return equality if number of bytes to

                                        /* compare is none. */

#if __i960_BIG_ENDIAN__

        cmpo    g0,SRC1         # check alignment of src1

#endif

         ld     (SRC1),LSW      # fetch word with at least first byte of src1

        notand  g1,3,g3         # extract word addr of start of src2

         ld     4(SRC1),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

        shlo    3,g0,g14        # compute shift count for src1

        subo    g14,0,g14       # adjust shift count for big endian

         lda    8(SRC1),SRC1    # advance src1 word addr

         bne.f  Lsrc2_unaligned # branch if src2 is NOT word aligned

                                /* src2 is word aligned */

        mov     LSW,g0

Lwloop2:                                # word comparing loop

        cmpo    SRC2,g0         # compare src1 and src2 words

         lda    0xff000000,g1   # byte extraction mask

        mov     MSW,LSW         # move msw of src1 to lsw

         ld     (SRC1),MSW      # pre-fetch next msw of src1

        addo    4,SRC1,SRC1     # post-increment src1 addr

         lda    4(g3),g3        # pre-increment src2 addr

         bne.f  Lcloop          # branch if src1 and src2 unequal

        scanbyte 0,g0           # check for null byte in src1 word

         ld     (g3),SRC2       # pre-fetch next word of src2

        mov     LSW,g0          # extract word of src1

         subi   4,g2,g2         # decrement maximum byte count

        bo.f    Lequal_exit     # branch if null byte encountered

        cmpibl.t 0,g2,Lwloop2   # branch if max_bytes not reached yet

        b       Lequal_exit     # strings were equal up through max_bytes

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       # adjust shift count for big endian

#endif

        eshro   g14,g4,LSW      # extract word of src1

         lda    8(SRC1),SRC1    # advance src1 word addr

         bne.f  Lsrc2_unaligned # branch if src2 is NOT word aligned

                                /* at least src2 is word aligned */

        mov     LSW,g0

Lwloop:                         # word comparing loop

        cmpo    SRC2,g0         # 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     (SRC1),MSW      # pre-fetch next msw of src1

        addo    4,SRC1,SRC1     # post-increment src1 addr

         lda    4(g3),g3        # pre-increment src2 addr

         bne.f  Lcloop          # branch if src1 and src2 unequal

        scanbyte 0,g0           # check for null byte in src1 word

         ld     (g3),SRC2       # pre-fetch next word of src2

        eshro   g14,g4,g0       # extract word of src1

         subi   4,g2,g2         # decrement maximum byte count

        bo.f    Lequal_exit     # branch if null byte encountered

        cmpibl.t 0,g2,Lwloop    # branch if max_bytes not reached yet

        b       Lequal_exit     # strings were equal up through max_bytes

Lcloop_setup:                   # setup for coming from Lsrc2_unaligned

        mov     LSW,g0          # 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     g0,g1,LSW       # extract next char of src1

        cmpobne.f LSW,g3,.diff  # check for equality

        cmpo    0,LSW           # 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

        subi    1,g2,g2         # decrement character counter

         bne.t  Lcloop          # branch if null not reached

                                /* words are equal up thru null byte */

Lequal_exit:

        mov     0,g14           # conform to register conventions

         lda    0,g0            # return zero, indicating equality

        bx      (g13)           # return

Lrett:

        ret

.diff:

        mov     0,g14

         bl     Lless_than_exit

Lgreater_than_exit:

        cmpibge.f 0,g2,Lequal_exit  # branch if difference is beyond max_bytes

        mov     1,g0

         bx     (g13)           # g0 = 1 (src1 > src2)

Lless_than_exit:

        cmpibge.f 0,g2,Lequal_exit  # branch if difference is beyond max_bytes

        subi    1,0,g0

         bx     (g13)           # g0 = -1 (src1 < src2)

Lsrc2_unaligned:

        notor   g1,3,g14        # first step in computing new src1 ptr

         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       # adjust shift count for big endian

#endif

        eshro   MSW,g6,SRC2     # extract word of src2

        cmpo    LSW,SRC2        # compare src1 and src2 words

         lda    4(g3),g1        # set new src2 ptr

         bne.f  Lcloop_setup    # first four bytes differ

        scanbyte 0,LSW          # check for null byte

        subo    g14,g0,g0       # second (final) step in computing new src1 ptr

        addi    g14,g2,g2       # compute new max_bytes too

         lda    (g13),g14       # prepare return pointer for Lrestart

         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)