1/*- 2 * Copyright (c) 1990 The Regents of the University of California. 3 * All rights reserved. 4 * 5 * This code is derived from software contributed to Berkeley by 6 * the Systems Programming Group of the University of Utah Computer 7 * Science Department. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 3. All advertising materials mentioning features or use of this software 18 * must display the following acknowledgement: 19 * This product includes software developed by the University of 20 * California, Berkeley and its contributors. 21 * 4. Neither the name of the University nor the names of its contributors 22 * may be used to endorse or promote products derived from this software 23 * without specific prior written permission. 24 * 25 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 26 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 27 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 28 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 29 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 30 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 31 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 32 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 33 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 34 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 35 * SUCH DAMAGE. 36 */ 37 38#include <machine/asm.h> 39 40;_sccsid: 41;.asciz "from: @(#)support.s 5.2 (Berkeley) 5/17/90" 42 43RCSID("$NetBSD: s_logb.S,v 1.4 1995/05/09 02:37:09 jtc Exp $") 44 45| logb(x) 46| returns the unbiased exponent of x, a signed integer in double precision, 47| except that logb(0) is -INF, logb(INF) is +INF, and logb(NAN) is that NAN. 48ENTRY(logb) 49 movw sp@(4),d0 50 movw #0x7FF0,d1 | exponent bits 51 andw d1,d0 | mask off all else 52 cmpw d1,d0 | max exponent? 53 bne Lfinite | no, is finite 54 fmoved sp@(4),fp0 | yes, infinite or NaN 55 fbun Ldone | NaN returns NaN 56 fabsx fp0 | +-inf returns inf 57 jra Ldone 58Lfinite: 59 fmoved sp@(4),fp0 | get entire number 60 fbne Lnonz | zero? 61 flog2x fp0 | yes, log(0) a convenient source of -inf 62 jra Ldone 63Lnonz: 64 fgetexpx fp0 | get exponent 65Ldone: 66 fmoved fp0,sp@- 67 movel sp@+,d0 68 movel sp@+,d1 69 rts 70