s_logb.S revision 1.1
1 1.1 jtc /*- 2 1.1 jtc * Copyright (c) 1990 The Regents of the University of California. 3 1.1 jtc * All rights reserved. 4 1.1 jtc * 5 1.1 jtc * This code is derived from software contributed to Berkeley by 6 1.1 jtc * the Systems Programming Group of the University of Utah Computer 7 1.1 jtc * Science Department. 8 1.1 jtc * 9 1.1 jtc * Redistribution and use in source and binary forms, with or without 10 1.1 jtc * modification, are permitted provided that the following conditions 11 1.1 jtc * are met: 12 1.1 jtc * 1. Redistributions of source code must retain the above copyright 13 1.1 jtc * notice, this list of conditions and the following disclaimer. 14 1.1 jtc * 2. Redistributions in binary form must reproduce the above copyright 15 1.1 jtc * notice, this list of conditions and the following disclaimer in the 16 1.1 jtc * documentation and/or other materials provided with the distribution. 17 1.1 jtc * 3. All advertising materials mentioning features or use of this software 18 1.1 jtc * must display the following acknowledgement: 19 1.1 jtc * This product includes software developed by the University of 20 1.1 jtc * California, Berkeley and its contributors. 21 1.1 jtc * 4. Neither the name of the University nor the names of its contributors 22 1.1 jtc * may be used to endorse or promote products derived from this software 23 1.1 jtc * without specific prior written permission. 24 1.1 jtc * 25 1.1 jtc * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 26 1.1 jtc * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 27 1.1 jtc * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 28 1.1 jtc * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 29 1.1 jtc * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 30 1.1 jtc * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 31 1.1 jtc * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 32 1.1 jtc * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 33 1.1 jtc * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 34 1.1 jtc * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 35 1.1 jtc * SUCH DAMAGE. 36 1.1 jtc */ 37 1.1 jtc 38 1.1 jtc #include <machine/asm.h> 39 1.1 jtc 40 1.1 jtc ;_sccsid: 41 1.1 jtc ;.asciz "from: @(#)support.s 5.2 (Berkeley) 5/17/90" 42 1.1 jtc _rcsid: 43 1.1 jtc .asciz "$Id: s_logb.S,v 1.1 1994/02/14 21:55:25 jtc Exp $" 44 1.1 jtc 45 1.1 jtc 46 1.1 jtc | logb(x) 47 1.1 jtc | returns the unbiased exponent of x, a signed integer in double precision, 48 1.1 jtc | except that logb(0) is -INF, logb(INF) is +INF, and logb(NAN) is that NAN. 49 1.1 jtc ENTRY(logb) 50 1.1 jtc movw sp@(4),d0 51 1.1 jtc movw #0x7FF0,d1 | exponent bits 52 1.1 jtc andw d1,d0 | mask off all else 53 1.1 jtc cmpw d1,d0 | max exponent? 54 1.1 jtc bne Lfinite | no, is finite 55 1.1 jtc fmoved sp@(4),fp0 | yes, infinite or NaN 56 1.1 jtc fbun Ldone | NaN returns NaN 57 1.1 jtc fabsx fp0 | +-inf returns inf 58 1.1 jtc jra Ldone 59 1.1 jtc Lfinite: 60 1.1 jtc fmoved sp@(4),fp0 | get entire number 61 1.1 jtc fbne Lnonz | zero? 62 1.1 jtc flog2x fp0 | yes, log(0) a convenient source of -inf 63 1.1 jtc jra Ldone 64 1.1 jtc Lnonz: 65 1.1 jtc fgetexpx fp0 | get exponent 66 1.1 jtc jra Ldone 67
Indexes created Sun Sep 28 16:09:52 GMT 2025