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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 "memcm_ca.s"
#ifdef  __PIC
        .pic
#endif
#ifdef  __PID
        .pid
#endif
/*
 * (c) copyright 1988,1992,1993 Intel Corp., all rights reserved
 */

/*
        procedure memcmp  (optimized assembler version for the CA)     

        result = memcmp (src1_addr, src2_addr, max_bytes)

        compare the byte array pointed to by src1_addr to the byte array
        pointed to by src2_addr.  Return 0 iff the arrays 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 array
        is in the last word of the program's allocated memory space.  This 
        is so because, in several cases, memcmp 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; byt 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  _memcmp
        .globl  __memcmp
        .leafproc       _memcmp, __memcmp
        .align  2
_memcmp:
#ifndef __PIC
        lda     Lrett,g14
#else
        lda     Lrett-(.+8)(ip),g14
#endif
__memcmp:
Lrestart:
#if __i960_BIG_ENDIAN__
        subo    1,g0,SRC1
        notand  SRC1,3,SRC1     # extract word addr of start of src1
#else
        notand  g0,3,SRC1       # extract word addr of start of src1
#endif
         lda    (g14),g13       # preserve return address
        cmpibge.f 0,g2,Lequal_exit      # return equality if number bytes 0
        notand  g1,3,g3         # extract word addr of start of src2
         ld     (SRC1),LSW      # fetch word with at least first byte of src1
        cmpo    g3,g1           # check alignment of src2
         ld     4(SRC1),MSW     # fetch second word of src1
        shlo    3,g0,g14        # compute shift count for src1
#if __i960_BIG_ENDIAN__
        subo    g14,0,g14       # adjust shift count for big endian.
#endif
         ld     (g3),SRC2       # fetch word with at least first byte of src2
        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

        mov     LSW,g0          # at least src2 is word aligned

         lda    0xff,g1

Lwloop:                         # word comparing loop
        cmpo    SRC2,g0         # compare src1 and src2 words
         lda    4(g3),g3        # pre-increment src2 addr
        mov     MSW,LSW         # move msw of src1 to lsw
         ld     (SRC1),MSW      # pre-fetch next msw of src1
        subi    4,g2,g2         # decrement maximum byte count
         bne.f  Lcloop          # branch if src1 and src2 unequal
        cmpi    0,g2
         ld     (g3),SRC2       # pre-fetch next word of src2
        eshro   g14,g4,g0       # extract word of src1
         lda    4(SRC1),SRC1    # post-increment src1 addr
        bl.t    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
        subo    4,g2,g2         # make up for later re-incrementing
         lda    0xff,g1         # byte extraction mask

Lcloop:                         # character comparing loop
#if __i960_BIG_ENDIAN__
        rotate  24,g1,g1        # shift mask for next byte
#endif
        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
#if ! __i960_BIG_ENDIAN__
        shlo    8,g1,g1         # shift mask for next byte
#endif
        subi    1,g2,g2         # decrement character counter
         b      Lcloop          # branch if null not reached


Lequal_exit:                    # words are equal up thru null byte
        mov     0,g14           # conform to register conventions
         lda    0,g0            # return zero, indicating equality
        bx      (g13)           # return
Lrett:
        ret

.diff:
        addo    4,g2,g2         # to make up for extra decrement in loop
         lda    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
#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
        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
         b      Lrestart                # continue with both string fetches shifted