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Annotation of 43BSDReno/lib/libc/tahoe/gen/modf.s, revision 1.1.1.1

1.1       root        1: /*
                      2:  * Copyright (c) 1988 Regents of the University of California.
                      3:  * All rights reserved.
                      4:  *
                      5:  * Redistribution and use in source and binary forms are permitted
                      6:  * provided that: (1) source distributions retain this entire copyright
                      7:  * notice and comment, and (2) distributions including binaries display
                      8:  * the following acknowledgement:  ``This product includes software
                      9:  * developed by the University of California, Berkeley and its contributors''
                     10:  * in the documentation or other materials provided with the distribution
                     11:  * and in all advertising materials mentioning features or use of this
                     12:  * software. Neither the name of the University nor the names of its
                     13:  * contributors may be used to endorse or promote products derived
                     14:  * from this software without specific prior written permission.
                     15:  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
                     16:  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
                     17:  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
                     18:  *
                     19:  * This code is derived from software contributed to Berkeley by
                     20:  * Computer Consoles Inc.
                     21:  */
                     22: 
                     23: #if defined(LIBC_SCCS) && !defined(lint)
                     24:        .asciz "@(#)modf.s      1.5 (Berkeley) 6/1/90"
                     25: #endif /* LIBC_SCCS and not lint */
                     26: 
                     27: /*
                     28:  * double modf (value, iptr)
                     29:  * double value, *iptr;
                     30:  *
                     31:  * Modf returns the fractional part of "value",
                     32:  * and stores the integer part indirectly through "iptr".
                     33:  *
                     34:  * This version uses floating point (look in ../fpe for
                     35:  * a much slower integer version).
                     36:  */
                     37: 
                     38: #include "DEFS.h"
                     39: 
                     40: ENTRY(modf, 0)
                     41:        ldd     4(fp)           # value
                     42:        cvdl    r2              # integerize
                     43:        bvs     1f              # did integer part overflow?
                     44:        cvld    r2              # integer part
                     45:        std     r0
                     46:        std     *12(fp)         # *iptr = r2
                     47:        ldd     4(fp)
                     48:        subd    r0              # value-(int)value
                     49:        std     r0              # return fraction
                     50:        ret
                     51: 1:
                     52:        /*
                     53:         * If the integer portion overflowed, mask out the fractional
                     54:         * bits in the double word instead of cvdl-ing.
                     55:         */
                     56:        ldd     4(fp)
                     57:        std     r0              # (r0,r1) = value
                     58:        shrl    $23,r0,r2       # extract sign,exponent of value
                     59:        andl2   $255,r2         # exponent
                     60:        subl2   $152,r2         # e-152
                     61:        /*
                     62:         * If it overflowed then value>=2^31 and e>=160
                     63:         * so we mask only r1 (low bits of fraction), not r0
                     64:         */
                     65:        mnegl   $1,r3
                     66:        shrl    r2,r3,r3        # -1>>(e-152) is neg mask to clear fraction
                     67:        mcoml   r3,r3           # complement mask
                     68:        andl2   r3,r1           # mask off truly fractional bits from fraction
                     69:        ldd     r0              # now (r0,r1) = integerized value
                     70:        std     *12(fp)         # *iptr = integerized
                     71:        ldd     4(fp)
                     72:        subd    r0
                     73:        std     r0              # return fraction
                     74:        ret

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