2013-12-06 12:04:52 +01:00
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/* $NetBSD: s_logb.S,v 1.7 2003/08/07 16:44:43 agc Exp $ */
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2011-02-14 20:36:03 +01:00
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/*-
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* Copyright (c) 1990 The Regents of the University of California.
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* All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* the Systems Programming Group of the University of Utah Computer
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* Science Department.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <machine/asm.h>
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2013-12-06 12:04:52 +01:00
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;_sccsid:
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;.asciz "from: @(#)support.s 5.2 (Berkeley) 5/17/90"
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RCSID("$NetBSD: s_logb.S,v 1.7 2003/08/07 16:44:43 agc Exp $")
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2011-02-14 20:36:03 +01:00
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2013-12-06 12:04:52 +01:00
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| logb(x)
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| returns the unbiased exponent of x, a signed integer in double precision,
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| except that logb(0) is -INF, logb(INF) is +INF, and logb(NAN) is that NAN.
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ENTRY(logb)
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movw %sp@(4),%d0
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movw #0x7FF0,%d1 | exponent bits
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andw %d1,%d0 | mask off all else
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cmpw %d1,%d0 | max exponent?
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bne Lfinite | no, is finite
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fmoved %sp@(4),%fp0 | yes, infinite or NaN
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fbun Ldone | NaN returns NaN
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fabsx %fp0 | +-inf returns inf
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jra Ldone
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Lfinite:
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fmoved %sp@(4),%fp0 | get entire number
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fbne Lnonz | zero?
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flog2x %fp0 | yes, log(0) a convenient source of -inf
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jra Ldone
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Lnonz:
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fgetexpx %fp0 | get exponent
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Ldone:
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2011-02-14 20:36:03 +01:00
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#ifndef __SVR4_ABI__
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fmoved %fp0,%sp@-
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movel %sp@+,%d0
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movel %sp@+,%d1
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#endif
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rts
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