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Annotation of 43BSDReno/lib/libc/tahoe/fpe/cvtld.s, revision 1.1.1.1

1.1       root        1: /*
                      2:  * Copyright (c) 1986 Regents of the University of California.
                      3:  * All rights reserved.
                      4:  *
                      5:  * This code is derived from software contributed to Berkeley by
                      6:  * Computer Consoles Inc.
                      7:  *
                      8:  * Redistribution and use in source and binary forms are permitted
                      9:  * provided that: (1) source distributions retain this entire copyright
                     10:  * notice and comment, and (2) distributions including binaries display
                     11:  * the following acknowledgement:  ``This product includes software
                     12:  * developed by the University of California, Berkeley and its contributors''
                     13:  * in the documentation or other materials provided with the distribution
                     14:  * and in all advertising materials mentioning features or use of this
                     15:  * software. Neither the name of the University nor the names of its
                     16:  * contributors may be used to endorse or promote products derived
                     17:  * from this software without specific prior written permission.
                     18:  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
                     19:  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
                     20:  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
                     21:  */
                     22: 
                     23: #if defined(SYSLIBC_SCCS) && !defined(lint)
                     24:        .asciz "@(#)cvtld.s     1.3 (Berkeley) 6/1/90"
                     25: #endif /* SYSLIBC_SCCS and not lint */
                     26: 
                     27: #include <tahoemath/fp.h>
                     28: #include "DEFS.h"
                     29: 
                     30: XENTRY(cvtld, R2|R3|R4|R5)
                     31:  #
                     32:  #Some initializations:
                     33:  #
                     34:        clrl    r4              # r4 - negative flag.
                     35:        clrl    r2              # r2 - exponent.
                     36:        movl    4(fp),r0        # fetch operand.
                     37:        movl    r0,r5           # need another copy.
                     38:        jeql    retzero         # return zero.
                     39:        jgtr    positive
                     40:        mnegl   r0,r0
                     41:        jvs     retmin          # return minimum integer.
                     42:        incl    r4              # remember it was negative.
                     43:        movl    r0,r5           # remember the negated value.
                     44:  #
                     45:  #Compute exponent:
                     46:  #
                     47: positive:
                     48:        ffs     r0,r1
                     49:        incl    r1
                     50:        addl2   r1,r2
                     51:        shrl    r1,r0,r0
                     52:        jneq    positive        # look for more set bits.
                     53:  #
                     54:  #we have the exponent in r2.
                     55:  #
                     56:        movl    r5,r0           # r0,r1 will hold the resulting f.p. number.
                     57:        clrl    r1
                     58:  #
                     59:  #Shift the fraction part to its proper place:
                     60:  #
                     61:        subl3   r2,$HID_POS,r3
                     62:        jlss    shiftr          # if less then zero we have to shift right.
                     63:        shll    r3,r0,r0        # else we shift left.
                     64:        jmp     shifted
                     65: shiftr:
                     66:        mnegl   r3,r3
                     67:        shrq    r3,r0,r0
                     68: shifted:
                     69:        andl2   $CLEARHID,r0    # clear the hidden bit.
                     70:        shal    $EXPSHIFT,r2,r2 # shift the exponent to its proper place.
                     71:        orl2    $EXPSIGN,r2     # set the exponent sign bit(to bias it).
                     72:        orl2    r2,r0           # combine exponent & fraction.
                     73:        bbc     $0,r4,sign_ok   # do we  have to set the sign bit?
                     74:        orl2    $SIGNBIT,r0     # yes...
                     75: sign_ok:
                     76:        ret
                     77: 
                     78: retzero:
                     79:        clrl    r0
                     80:        clrl    r1
                     81:        ret
                     82: 
                     83: retmin:
                     84:        movl    $0xd0000000,r0
                     85:        clrl    r1
                     86:        ret
                     87: 
                     88: 
                     89:        

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