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Annotation of 43BSDTahoe/lib/libc/gen/gen.tahoe/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 the above copyright notice and this paragraph are
                      7:  * duplicated in all such forms and that any documentation,
                      8:  * advertising materials, and other materials related to such
                      9:  * distribution and use acknowledge that the software was developed
                     10:  * by the University of California, Berkeley.  The name of the
                     11:  * University may not be used to endorse or promote products derived
                     12:  * from this software without specific prior written permission.
                     13:  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
                     14:  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
                     15:  * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
                     16:  *
                     17:  * This code is derived from software contributed to Berkeley by
                     18:  * Computer Consoles Inc.
                     19:  */
                     20: 
                     21: #if defined(LIBC_SCCS) && !defined(lint)
                     22:        .asciz "@(#)modf.s      1.4 (Berkeley) 6/27/88"
                     23: #endif /* LIBC_SCCS and not lint */
                     24: 
                     25: /*
                     26:  * double modf (value, iptr)
                     27:  * double value, *iptr;
                     28:  *
                     29:  * Modf returns the fractional part of "value",
                     30:  * and stores the integer part indirectly through "iptr".
                     31:  *
                     32:  * This version uses floating point (look in ../fpe for
                     33:  * a much slower integer version).
                     34:  */
                     35: 
                     36: #include "DEFS.h"
                     37: 
                     38: ENTRY(modf, 0)
                     39:        ldd     4(fp)           # value
                     40:        cvdl    r2              # integerize
                     41:        bvs     1f              # did integer part overflow?
                     42:        cvld    r2              # integer part
                     43:        std     r0
                     44:        std     *12(fp)         # *iptr = r2
                     45:        ldd     4(fp)
                     46:        subd    r0              # value-(int)value
                     47:        std     r0              # return fraction
                     48:        ret
                     49: 1:
                     50:        /*
                     51:         * If the integer portion overflowed, mask out the fractional
                     52:         * bits in the double word instead of cvdl-ing.
                     53:         */
                     54:        ldd     4(fp)
                     55:        std     r0              # (r0,r1) = value
                     56:        shrl    $23,r0,r2       # extract sign,exponent of value
                     57:        andl2   $255,r2         # exponent
                     58:        subl2   $152,r2         # e-152
                     59:        /*
                     60:         * If it overflowed then value>=2^31 and e>=160
                     61:         * so we mask only r1 (low bits of fraction), not r0
                     62:         */
                     63:        mnegl   $1,r3
                     64:        shrl    r2,r3,r3        # -1>>(e-152) is neg mask to clear fraction
                     65:        mcoml   r3,r3           # complement mask
                     66:        andl2   r3,r1           # mask off truly fractional bits from fraction
                     67:        ldd     r0              # now (r0,r1) = integerized value
                     68:        std     *12(fp)         # *iptr = integerized
                     69:        ldd     4(fp)
                     70:        subd    r0
                     71:        std     r0              # return fraction
                     72:        ret

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