1 /* $NetBSD: s_logb.S,v 1.7 2003/08/07 16:44:43 agc Exp $ */ 2 3 /*- 4 * Copyright (c) 1990 The Regents of the University of California. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * the Systems Programming Group of the University of Utah Computer 9 * Science Department. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 3. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 */ 35 36 #include <machine/asm.h> 37 38 ;_sccsid: 39 ;.asciz "from: @(#)support.s 5.2 (Berkeley) 5/17/90" 40 41 RCSID("$NetBSD: s_logb.S,v 1.7 2003/08/07 16:44:43 agc Exp $") 42 43 | logb(x) 44 | returns the unbiased exponent of x, a signed integer in double precision, 45 | except that logb(0) is -INF, logb(INF) is +INF, and logb(NAN) is that NAN. 46 ENTRY(logb) 47 movw %sp@(4),%d0 48 movw #0x7FF0,%d1 | exponent bits 49 andw %d1,%d0 | mask off all else 50 cmpw %d1,%d0 | max exponent? 51 bne Lfinite | no, is finite 52 fmoved %sp@(4),%fp0 | yes, infinite or NaN 53 fbun Ldone | NaN returns NaN 54 fabsx %fp0 | +-inf returns inf 55 jra Ldone 56 Lfinite: 57 fmoved %sp@(4),%fp0 | get entire number 58 fbne Lnonz | zero? 59 flog2x %fp0 | yes, log(0) a convenient source of -inf 60 jra Ldone 61 Lnonz: 62 fgetexpx %fp0 | get exponent 63 Ldone: 64 #ifndef __SVR4_ABI__ 65 fmoved %fp0,%sp@- 66 movel %sp@+,%d0 67 movel %sp@+,%d1 68 #endif 69 rts 70
Indexes created Sat Sep 20 22:09:52 GMT 2025