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/*-
* Copyright (c) 1990 The Regents of the University of California.
* All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* the Systems Programming Group of the University of Utah Computer
* Science Department.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <machine/asm.h>
;_sccsid:
;.asciz "from: @(#)support.s 5.2 (Berkeley) 5/17/90"
RCSID("$NetBSD: s_logb.S,v 1.4 1995/05/09 02:37:09 jtc Exp $")
| logb(x)
| returns the unbiased exponent of x, a signed integer in double precision,
| except that logb(0) is -INF, logb(INF) is +INF, and logb(NAN) is that NAN.
ENTRY(logb)
movw sp@(4),d0
movw #0x7FF0,d1 | exponent bits
andw d1,d0 | mask off all else
cmpw d1,d0 | max exponent?
bne Lfinite | no, is finite
fmoved sp@(4),fp0 | yes, infinite or NaN
fbun Ldone | NaN returns NaN
fabsx fp0 | +-inf returns inf
jra Ldone
Lfinite:
fmoved sp@(4),fp0 | get entire number
fbne Lnonz | zero?
flog2x fp0 | yes, log(0) a convenient source of -inf
jra Ldone
Lnonz:
fgetexpx fp0 | get exponent
Ldone:
fmoved fp0,sp@-
movel sp@+,d0
movel sp@+,d1
rts
|
