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Annotation of 43BSDReno/lib/libc/tahoe/fpe/cvtuf.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 "@(#)cvtuf.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(cvtuf, R2|R3|R4|R5)
                     31:  #
                     32:  #     Some initializations:
                     33:  #
                     34:        clrl    r1
                     35:        clrl    r2              # r2 - exponent.
                     36:        movl    4(fp),r0        # fetch operand.
                     37:        jeql    retzero         # return zero.
                     38:  # 
                     39:  #     Compute exponent:
                     40:  #
                     41: positive:
                     42:        ffs     r0,r1
                     43:        incl    r1
                     44:        addl2   r1,r2
                     45:        shrl    r1,r0,r0
                     46:        jneq    positive        # look for more set bits.
                     47:  #
                     48:  # we have the exponent in r2.
                     49:  #
                     50:        movl    4(fp),r0        # r0 will hold the resulting f.p. number.
                     51:  #
                     52:  #     Shift the fraction part to its proper place:
                     53:  #
                     54:        subl3   r2,$HID_POS,r3
                     55:        jlss    shiftr          # if less then zero we have to shift right.
                     56:        shll    r3,r0,r0        # else we shift left.
                     57:        jmp     shifted
                     58: shiftr:
                     59:        mnegl   r3,r3
                     60:        shrl    r3,r0,r0
                     61: shifted:
                     62:        andl2   $CLEARHID,r0    # clear the hidden bit.
                     63:        shal    $EXPSHIFT,r2,r2 # shift the exponent to its proper place.
                     64:        orl2    $EXPSIGN,r2     # set the exponent sign bit(to bias it).
                     65:        orl2    r2,r0           # combine exponent & fraction.
                     66: sign_ok:
                     67:        ret
                     68: 
                     69: retzero:
                     70:        clrl    r0
                     71:        ret
                     72: 
                     73:        

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