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/*
 *  (c) Copyright 1986 HEWLETT-PACKARD COMPANY
 *
 *  To anyone who acknowledges that this file is provided "AS IS"
 *  without any express or implied warranty:
 *      permission to use, copy, modify, and distribute this file
 *  for any purpose is hereby granted without fee, provided that
 *  the above copyright notice and this notice appears in all
 *  copies, and that the name of Hewlett-Packard Company not be
 *  used in advertising or publicity pertaining to distribution
 *  of the software without specific, written prior permission.
 *  Hewlett-Packard Company makes no representations about the
 *  suitability of this software for any purpose.
 */

/* strcmp(s1, s2) */
/* returns integer: < 0 iff s1 lexicographically less than s2 */
/*                  > 0 iff s1 lexicographically greater than s2 */
/*                  = 0 iff s1 lexicographically equal to s2 */
/*                  = 0 iff s1 lexicographically equal to s2 */
/*                  quit after n charachters */
#include "DEFS.h"

#define s1        26
#define s2        25
#define tmp1      19
#define s2word    20
#define tmp3      21
#define tmp7      22
#define s1word    29
#define save       1
#define tmp6      23
#define tmp5      28
#define count     24

ENTRY(strncmp)
        combt,<,n       r0,count,search /* N <= 0 yields equality */
        bv      r0(rp)                  /* */
        copy    0,ret0                  /* return 0 (DELAY SLOT) */
search: combf,=,n       s1,s2,findout   /* s1 != s2? */
        bv      r0(rp)                  /* */
        copy    0,ret0                  /* return 0 (delay slot)         */
findout:
        comibf,=,n      0,s1,checks1    /* s1 == NULL?   */
        ldbs    0(0,s2),ret0            /* */
        bv      r0(rp)                  /* */
        subi    0,ret0,ret0             /* ret0 <- -*s2 */
checks1:
        comibf,=,n      0,s2,checkitout /* s2 == NULL?   */
        bv      r0(rp)                  /* */
        ldbs    0(0,s1),28              /* return *s1 */

checkitout:
        extru   s2,31,2,tmp1            /* Extract the low two bits of the s2. */
        extru   s1,31,2,tmp5            /* Extract the low two bits of the s1 */
        sub,=   tmp5,tmp1,tmp3          /* Are s1 & s2 aligned with each other? */
        b       not_aligned             /* It's more complicated (not_aligned) */
        dep     0,31,2,s1               /* Compute word address of s1 (DELAY SLOT) */
        dep     0,31,2,s2               /* Compute word address of s2 */
        ldwm    4(0,s1),s1word          /* get next s1 word  s1+=4 */
        combt,= tmp5,r0,skipmask        /* skip masking, if we can */
        ldwm    4(0,s2),s2word          /* get next s2 word  s2+=4 (DELAY SLOT) */
        add     tmp5,count,count        /* bump count by the number of bytes */
                                        /*  we are going to mask */
        sh3add  tmp5,r0,save            /* save now has number of bits to mask */
        mtctl   save,11
        zvdepi  -2,32,save              /* load save with proper mask */
        or      save,s1word,s1word      /* mask s1word (s1) */
        or      save,s2word,s2word      /* mask s2word (s2) */
        

skipmask:
        combt,=,n       s1word,s2word,chknulls  /* are these words equal? */

checkbyte:
        extru   s1word,7,8,tmp3         /* get first byte (character) */
ckbyte2:        extru   s2word,7,8,tmp7         /* get first byte (character) */
        combf,= tmp3,tmp7,done          /* quit if first byte is not equal */
        sub     tmp3,tmp7,ret0          /* return difference (delay slot) */
        comibt,=,n      0,tmp3,done     /* have we reached the end of string */
                                        /* if so done ret0 already has zero */
        addibt,<=,n     -1,count,done   /* have we checked N chars? ret0 == 0 */
        extru   s1word,15,8,tmp3        /* get second byte (character) */
        extru   s2word,15,8,tmp7        /* get second byte (character)   */
        combf,= tmp3,tmp7,done          /* quit if second byte is not equal */
        sub     tmp3,tmp7,ret0          /* return difference (delay slot) */
        comibt,=,n      0,tmp3,done     /* have we reached the end of string */
                                        /* if so done ret0 already has zero */
        addibt,<=,n     -1,count,done   /* have we checked N chars? */
        extru   s1word,23,8,tmp3        /* get third byte (character) */
        extru   s2word,23,8,tmp7        /* get third byte (character)    */
        combf,= tmp3,tmp7,done          /* done if third byte is not equal */
        sub     tmp3,tmp7,ret0          /* return difference (delay slot) */
        comibt,=,n      0,tmp3,done     /* have we reached the end of string */
                                        /* if so done ret0 already has zero */
        addibt,<=,n     -1,count,done   /* have we checked N chars? */
        extru   s1word,31,8,tmp3        /* get last byte (character) */
        extru   s2word,31,8,tmp7        /* get last byte (character)     */
        bv      r0(rp)                  /* */
        sub     tmp3,tmp7,ret0          /*  the last characters in the word is */
                                        /*   where the  difference is, so return */
                                        /*    the difference and we're outta here */


chknulls:
        addibt,<=,n     -4,count,zero   /* have we checked N chars? */
        uxor,nbz        s1word,0,0      /* don't have to check s2   Just quit */
        bv      r0(rp)                  /* */
        copy    0,28                    /* return 0 */
        ldwm    4(0,s2),s2word          /* get next s2 word  s2+=4 */
        b       skipmask                /* keep checking */
        ldwm    4(0,s1),s1word          /* get next s1 word  s1+=4 */


not_aligned:
        dep     r0,31,2,s2              /* Compute word address of s2 */
        combt,<,n       r0,tmp3,shifts1 /* Do we shift s1 or s2 */
        sh3add  tmp3,r0,tmp3            /* eight bits per byte so mul by 8 */
        ldwm    4(0,s1),s1word          /* get first word of s1 */
        ldwm    4(0,s2),s2word          /* get first word or s2 */
        combt,=,n       r0,tmp5,masks2  /* Do we need to mask beginning of s1 */
        add     tmp5,count,count        /* bump count by the number of bytes */
                                        /*  we are going to mask */
        sh3add  tmp5,r0,save            /* save now has number of bits to mask */
        mtctl   save,11
        zvdepi  -2,32,save              /* load save with proper mask */
        or      save,s1word,s1word      /* */
masks2: sh3add  tmp1,r0,save            /* save now has number of bits to mask */
        mtctl   save,11
        zvdepi  -2,32,save              /* load save with proper mask */
        or      save,s2word,s2word      /* */
        mtctl   tmp3,11                 /* Move shift amount to CR11 */
more:   uxor,nbz        s2word,r0,r0            /* Is there a null in first word         */
        b,n     chunk1                  /* */
        ldwm    4(0,s2),tmp7            /* load second word to enable us to shift */
        vshd    s2word,tmp7,s2word      /* */
        combf,=,n       s1word,s2word,ckbyte2   /* */
        extru   s1word,7,8,tmp3         /* get first byte (DELAY SLOT) */
        addibt,<=,n     -4,count,zero   /* have we checked N chars? */
        uxor,nbz        s1word,0,0      /* even though they're equal we could be done */
        b,n     zero    
        copy    tmp7,s2word             /* */
        b       more                    /* keep checking */
        ldwm    4(0,s1),s1word          /* get next s1 (DELAY SLOT) */

chunk1: 
        vshd    s2word,r0,s2word        /* */
        b       ckbyte2                 /* */
        extru   s1word,7,8,tmp3         /* */


shifts1:
        sh3add  tmp3,r0,tmp3            /* eight bits per byte so mul by 4 */
        sub     r0,tmp3,tmp3            /* Get negative value for left shift */
        ldwm    4(0,s2),s2word          /* get first word of s2 */
        ldwm    4(0,s1),s1word          /* get first word or s1 */
        combt,=,n       r0,tmp1,masks1  /* Do we need to mask beginning of s2 */
        add     tmp1,count,count        /* bump count by the number of bytes */
                                        /*  we are going to mask */
        sh3add  tmp1,r0,save            /* save now has number of bits to mask */
        mtctl   save,11
        zvdepi  -2,32,save              /* load save with proper mask */
        or      save,s2word,s2word      /* */
masks1: sh3add  tmp5,r0,save            /* save now has number of bits to mask */
        mtctl   save,11
        zvdepi  -2,32,save              /* load save with proper mask */
        or      save,s1word,s1word      /* */
        mtctl   tmp3,11                 /* Move shift amount to CR11 */
more1:  uxor,nbz        s1word,r0,r0            /* Is there a null in first byte         */
        b,n     chunk2                  /* */
        ldwm    4(0,s1),tmp7            /* load second word to enable us to shift */
        vshd    s1word,tmp7,s1word      /* */
        combf,=,n       s2word,s1word,ckbyte2   /* */
        extru   s1word,7,8,tmp3         /* get first byte (DELAY SLOT) */
        addibt,<=,n     -4,count,zero   /* have we checked N chars? */
        uxor,nbz        s2word,0,0      /* even though they're equal we could be done */
        b,n     zero                    /* zero ret0 and quit */
        copy    tmp7,s1word             /* */
        b       more1                   /* keep checking */
        ldwm    4(0,s2),s2word          /* get next s2 (DELAY SLOT) */

chunk2: 
        vshd    s1word,r0,s1word        /* */
        b       ckbyte2                 /* */
        extru   s1word,7,8,tmp3         /* */

zero:   copy    r0,ret0
done:
EXIT(strncmp)