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Annotation of Net2/arch/tahoe/math/kldexpf.s, revision 1.1

1.1     ! root        1: /*-
        !             2:  * Copyright (c) 1985 The 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, with or without
        !             9:  * modification, are permitted provided that the following conditions
        !            10:  * are met:
        !            11:  * 1. Redistributions of source code must retain the above copyright
        !            12:  *    notice, this list of conditions and the following disclaimer.
        !            13:  * 2. Redistributions in binary form must reproduce the above copyright
        !            14:  *    notice, this list of conditions and the following disclaimer in the
        !            15:  *    documentation and/or other materials provided with the distribution.
        !            16:  * 3. All advertising materials mentioning features or use of this software
        !            17:  *    must display the following acknowledgement:
        !            18:  *     This product includes software developed by the University of
        !            19:  *     California, Berkeley and its contributors.
        !            20:  * 4. Neither the name of the University nor the names of its contributors
        !            21:  *    may be used to endorse or promote products derived from this software
        !            22:  *    without specific prior written permission.
        !            23:  *
        !            24:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
        !            25:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
        !            26:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
        !            27:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
        !            28:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
        !            29:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
        !            30:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
        !            31:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
        !            32:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
        !            33:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
        !            34:  * SUCH DAMAGE.
        !            35:  *
        !            36:  *     @(#)Kldexpf.s   7.1 (Berkeley) 12/6/90
        !            37:  */
        !            38: 
        !            39: #include "../tahoe/SYS.h"
        !            40: #include "../math/fp.h"
        !            41: #include "../math/Kfp.h"
        !            42: 
        !            43: /* @(*)Kldexpf.s       4.2 (Berkeley) 12/21/80
        !            44:  *     Tahoe           2/2/83
        !            45:  *
        !            46:  * float Kldexpf (op_most, op_least, exp, hfs)
        !            47:  *
        !            48:  * Ldexp returns value*2**exp, if that result is in range.
        !            49:  * If underflow occurs, it returns zero.  If overflow occurs,
        !            50:  * it returns a value of appropriate sign and largest
        !            51:  * possible magnitude.  In case of either overflow or underflow,
        !            52:  * the external int "errno" is set to ERANGE.  Note that errno is
        !            53:  * not modified if no error occurs, so if you intend to test it
        !            54:  * after you use Kldexpf, you had better set it to something
        !            55:  * other than ERANGE first (zero is a reasonable value to use).
        !            56:  */
        !            57: 
        !            58:        .text
        !            59: ENTRY(Kldexpf, R2)
        !            60:        movl    4(fp),r0        /* Fetch "value" */
        !            61:        movl    8(fp),r1
        !            62: 
        !            63:        andl3   $EXPMASK,r0,r2  /* r2 := shifted biased exponent */
        !            64:        jeql    ld1             /* If it's zero, we're done */
        !            65:        shar    $EXPSHIFT,r2,r2 /* shift to get value of exponent  */
        !            66: 
        !            67:        addl2   12(fp),r2       /* r2 := new biased exponent */
        !            68:        jleq    under           /* if it's <= 0, we have an underflow */
        !            69:        cmpl    r2,$256         /* Otherwise check if it's too big */
        !            70:        jgeq    over            /* jump if overflow */
        !            71: /*
        !            72:  *     Construct the result and return
        !            73:  */
        !            74:        andl2   $0!EXPMASK,r0   /* clear old exponent */
        !            75:        shal    $EXPSHIFT,r2,r2 /* Put the exponent back in the result */
        !            76:        orl2    r2,r0
        !            77: ld1:   ret
        !            78: /*
        !            79:  *     Underflow
        !            80:  */
        !            81: under: clrl    r0              /* Result is zero */
        !            82:        clrl    r1
        !            83:        orl2    $HFS_UNDF,*16(fp)
        !            84:        jmp     err             /* Join general error code */
        !            85: /*
        !            86:  *     Overflow
        !            87:  */
        !            88: over:  movl    huge0,r0        /* Largest possible floating magnitude */
        !            89:        movl    huge1,r1
        !            90:        orl2    $HFS_OVF,*16(fp)
        !            91:        orl2    $SIGNBIT,r0     /* If arg < 0, make result negative */
        !            92: 
        !            93: err:   orl2    $HFS_RANGE,*16(fp)      /* Indicate range error */
        !            94:        ret
        !            95: 
        !            96:        .data
        !            97: huge0: .long   0x7fffffff
        !            98: huge1: .long   0xffffffff

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