source: trunk/libs/newlib/src/newlib/libc/machine/i960/strcpy_ca.S @ 690

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

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

        dest_addr = strcpy (dest_addr, src_addr)

        copy the null terminated string pointed to by src_addr to 
        the string space pointed to by dest_addr.  Return the original
        dest_addr.

        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  dest ptr;  4 bytes of src
        g3  src ptr (word aligned)
        g4  dest ptr (word aligned)
        g5  0xff  --  byte extraction mask
        g6  lsw of double word for extraction of 4 bytes (little endian)
            msw of double word for extraction of 4 bytes (big endian)
        g7  msw of double word for extraction of 4 bytes (little endian)
            lsw of double word for extraction of 4 bytes (big endian)
        g13 return address
        g14 byte extracted.  When reaches null byte, which is zero, we will
            be in conformance with register conventions, and can return to
            the caller with a clear conscience.

        procedure strcat

        dest_addr = strcat (dest_addr, src_addr)

        Appends the string pointed to by src_addr to the string pointed
        to by dest_addr.  The first character of the source string is
        copied to the location initially occupied by the trailing null
        byte of the destination string.  Thereafter, characters are copied
        from the source to the destination up thru the null byte that
        trails the source string.
*/

#if __i960_BIG_ENDIAN__
#define MSW g6
#define LSW g7
#else
#define LSW g6
#define MSW g7
#endif

        .globl  _strcpy, _strcat
        .globl  __strcpy, __strcat
        .leafproc       _strcpy, __strcpy
        .leafproc       _strcat, __strcat
        .align  2
_strcat:
#ifndef __PIC
        lda     Lrett,g14
#else
        lda     Lrett-(.+8)(ip),g14
#endif
__strcat:
        notand  g0,3,g4         # extract word addr of start of dest
        lda     (g14),g13       # preserve return address
        and     g0,3,LSW        # extract byte offset of dest
        ld      (g4),MSW        # fetch word containing at least first byte
        shlo    3,LSW,g14       # get shift count for making mask for first word
        subi    1,0,LSW         # mask initially all ones
#if __i960_BIG_ENDIAN__
        shro    g14,LSW,LSW     # get mask for bytes needed from first word
        lda     0xff000000,g5   # byte extraction mask
#else
        shlo    g14,LSW,LSW     # get mask for bytes needed from first word
        lda     0xff,g5         # byte extraction mask
#endif
        notor   MSW,LSW,MSW     # set unneeded bytes to all ones
Lsearch_for_word_with_null:
        scanbyte 0,MSW          # check for null byte
        lda     4(g4),g4        # post-increment dest word pointer
        mov     MSW,LSW         # keep a copy of current word
        ld      (g4),MSW        # fetch next word of dest
        bno.t   Lsearch_for_word_with_null      # branch if null not found yet
        and     g5,LSW,g14      # extract byte
        cmpo    0,g14           # branch if null is first byte of word
        subo    4,g4,g4         # move dest word ptr back to word with null
        notand  g1,3,g3         # extract word addr of start of src
        lda     (g4),g2         # set dest byte ptr to 1st byte of word w/ null
        be.f    Lcase_14
Lsearch_for_null:
#if __i960_BIG_ENDIAN__
        shro    8,g5,g5         # move mask down to next byte
#else
        shlo    8,g5,g5         # move mask up to next byte
#endif
        lda     1(g2),g2        # move dest byte ptr to next byte
        and     g5,LSW,g14      # extract byte
        cmpobne.t 0,g14,Lsearch_for_null        # branch if null is not yet found
        lda     0xff,g5         # byte extraction mask
        b       Lcase_235.a

        
_strcpy:
#ifndef __PIC
        lda     Lrett,g14
#else
        lda     Lrett-(.+8)(ip),g14
#endif
__strcpy:
        notand  g0,3,g4         # extract word addr of start of dest
        lda     (g14),g13       # preserve return address
        cmpo    g0,g4           # check alignment of dest
        lda     0xff,g5         # load mask for byte extraction
        notand  g1,3,g3         # extract word addr of start of src
        bne.f   Lcase_235       # branch if dest is NOT word aligned

Lcase_14:
        cmpo    g3,g1           # check alignment of src
        ld      (g3),LSW        # fetch word containing at least first byte
        shlo    3,g1,g1         # compute shift count
        lda     4(g3),g3        # advance src word addr
#if __i960_BIG_ENDIAN__
        lda     0xff,g5         # byte extraction mask
#endif
        bne.f   Lcase_4         # branch if src is NOT word aligned

Lcase_1:                                # src and dest are word aligned
        subo    4,g4,g4         # store is pre-incrementing;  back up dest addr
Lcase_1_wloop:                  # word copying loop
        scanbyte 0,LSW          # check for null byte in src word
        lda     (LSW),g2        # keep a copy of the src word
        addo    4,g4,g4         # pre-increment dest addr
        ld      (g3),LSW        # pre-fetch next word of src
        addo    4,g3,g3         # post-increment src addr
        bo.f    Lcase_1_cloop   # branch if word contains null byte
        st      g2,(g4)         # store word in dest string
        b       Lcase_1_wloop

Lcase_3_cloop:
Lcase_1_cloop:                  # character copying loop
#if __i960_BIG_ENDIAN__
        rotate  8,g2,g2         # move next byte into position for extraction
        and     g5,g2,g14       # extract next char
#else
        and     g5,g2,g14       # extract next char
        shro    8,g2,g2         # move next byte into position for extraction
#endif
        cmpo    0,g14           # check for null byte
        stob    g14,(g4)        # store the byte in dest
        lda     1(g4),g4        # post-increment dest byte addr
        bne.t   Lcase_1_cloop   # branch if null not reached

Lexit_code:
        bx      (g13)           # g0 = addr of dest;  g14 = 0
Lrett:
        ret

Lcase_3:                                # src is word aligned; dest is not
        addo    4,g4,g4         # move dest word ptr to first word boundary
        mov     LSW,MSW         # make copy of first word of src
        lda     0,g1            # initialize shift count to zero

Lcase_25:
Lcase_3_cloop_at_start:         # character copying loop for start of dest str
#if __i960_BIG_ENDIAN__
        rotate  8,MSW,MSW       # move next byte into position for extraction
        and     g5,MSW,g14      # extract next char
#else
        and     g5,MSW,g14      # extract next char
        shro    8,MSW,MSW       # move next byte into position for extraction
#endif
        cmpo    0,g14           # check for null byte
        stob    g14,(g2)        # store the byte in dest
        lda     1(g2),g2        # post-increment dest ptr
        be.f    Lexit_code      # branch if null byte reached
        cmpo    g2,g4           # have we reached word boundary in dest?
        lda     8(g1),g1        # augment the shift counter
        bne.t   Lcase_3_cloop_at_start

Lcase_4:
        ld      (g3),MSW        # fetch msw of operand for double shift
#if __i960_BIG_ENDIAN__
        subo    g1,0,g1         # Adjust shift count for big endian.
#endif

Lcase_3_wloop:
        eshro   g1,g6,g2        # extract 4 bytes of src
        lda     4(g3),g3        # post-increment src word addr
        scanbyte 0,g2           # check for null byte
        lda     (MSW),LSW       # move msw to lsw
        ld      (g3),MSW        # pre-fetch msw of operand for double shift
        bo.f    Lcase_3_cloop   # branch if word contains null byte
        st      g2,(g4)         # store 4 bytes to dest
        addo    4,g4,g4         # post-increment dest ptr
        b       Lcase_3_wloop

Lcase_235:
        lda     (g0),g2         # copy dest ptr 
Lcase_235.a:
        cmpo    g3,g1           # check alignment of src
        ld      (g3),LSW        # fetch word containing at least first byte
        and     3,g1,g14        # compute shift count
        lda     4(g3),g3        # advance src word addr
        shlo    3,g14,g1        
        be.t    Lcase_3         # branch if dest is word aligned
        or      g4,g14,g14      # is src earlier in word, later, or sync w/ dst
        ld      (g3),MSW        # pre-fetch second half
        cmpo    g2,g14          # < indicates first word of dest has more bytes
        lda     4(g4),g4        # move dest word addr to first word boundary
                                /* than first word of source. */
#if __i960_BIG_ENDIAN__
        subo    g1,0,g14        # Adjust shift count for big endian.
        eshro   g14,g6,g14      # extract four bytes
        bge.f   1f
#else
        eshro   g1,g6,g14       # extract four bytes
        bg.f    1f
#endif
        mov     MSW,LSW
        lda     4(g3),g3        # move src word addr to second word boundary
1:
        mov     g14,MSW
        b       Lcase_25

/* end of strcpy */