/* $NetBSD: mul.S,v 1.1 2005/12/20 19:28:50 christos Exp $ */ /* * Copyright (c) 1992, 1993 * The Regents of the University of California. All rights reserved. * * This software was developed by the Computer Systems Engineering group * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and * contributed to Berkeley. * * 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. * * from: Header: mul.s,v 1.5 92/06/25 13:24:03 torek Exp */ #include <machine/asm.h> #if defined(LIBC_SCCS) && !defined(lint) #if 0 .asciz "@(#)mul.s 8.1 (Berkeley) 6/4/93" #else RCSID("$NetBSD: mul.S,v 1.1 2005/12/20 19:28:50 christos Exp $") #endif #endif /* LIBC_SCCS and not lint */ /* * Signed multiply, from Appendix E of the Sparc Version 8 * Architecture Manual. * * Returns %o0 * %o1 in %o1%o0 (i.e., %o1 holds the upper 32 bits of * the 64-bit product). * * This code optimizes short (less than 13-bit) multiplies. */ FUNC(.mul) mov %o0, %y ! multiplier -> Y andncc %o0, 0xfff, %g0 ! test bits 12..31 be Lmul_shortway ! if zero, can do it the short way andcc %g0, %g0, %o4 ! zero the partial product and clear N and V /* * Long multiply. 32 steps, followed by a final shift step. */ mulscc %o4, %o1, %o4 ! 1 mulscc %o4, %o1, %o4 ! 2 mulscc %o4, %o1, %o4 ! 3 mulscc %o4, %o1, %o4 ! 4 mulscc %o4, %o1, %o4 ! 5 mulscc %o4, %o1, %o4 ! 6 mulscc %o4, %o1, %o4 ! 7 mulscc %o4, %o1, %o4 ! 8 mulscc %o4, %o1, %o4 ! 9 mulscc %o4, %o1, %o4 ! 10 mulscc %o4, %o1, %o4 ! 11 mulscc %o4, %o1, %o4 ! 12 mulscc %o4, %o1, %o4 ! 13 mulscc %o4, %o1, %o4 ! 14 mulscc %o4, %o1, %o4 ! 15 mulscc %o4, %o1, %o4 ! 16 mulscc %o4, %o1, %o4 ! 17 mulscc %o4, %o1, %o4 ! 18 mulscc %o4, %o1, %o4 ! 19 mulscc %o4, %o1, %o4 ! 20 mulscc %o4, %o1, %o4 ! 21 mulscc %o4, %o1, %o4 ! 22 mulscc %o4, %o1, %o4 ! 23 mulscc %o4, %o1, %o4 ! 24 mulscc %o4, %o1, %o4 ! 25 mulscc %o4, %o1, %o4 ! 26 mulscc %o4, %o1, %o4 ! 27 mulscc %o4, %o1, %o4 ! 28 mulscc %o4, %o1, %o4 ! 29 mulscc %o4, %o1, %o4 ! 30 mulscc %o4, %o1, %o4 ! 31 mulscc %o4, %o1, %o4 ! 32 mulscc %o4, %g0, %o4 ! final shift ! If %o0 was negative, the result is ! (%o0 * %o1) + (%o1 << 32)) ! We fix that here. tst %o0 bge 1f rd %y, %o0 ! %o0 was indeed negative; fix upper 32 bits of result by subtracting ! %o1 (i.e., return %o4 - %o1 in %o1). retl sub %o4, %o1, %o1 1: retl mov %o4, %o1 Lmul_shortway: /* * Short multiply. 12 steps, followed by a final shift step. * The resulting bits are off by 12 and (32-12) = 20 bit positions, * but there is no problem with %o0 being negative (unlike above). */ mulscc %o4, %o1, %o4 ! 1 mulscc %o4, %o1, %o4 ! 2 mulscc %o4, %o1, %o4 ! 3 mulscc %o4, %o1, %o4 ! 4 mulscc %o4, %o1, %o4 ! 5 mulscc %o4, %o1, %o4 ! 6 mulscc %o4, %o1, %o4 ! 7 mulscc %o4, %o1, %o4 ! 8 mulscc %o4, %o1, %o4 ! 9 mulscc %o4, %o1, %o4 ! 10 mulscc %o4, %o1, %o4 ! 11 mulscc %o4, %o1, %o4 ! 12 mulscc %o4, %g0, %o4 ! final shift /* * %o4 has 20 of the bits that should be in the low part of the * result; %y has the bottom 12 (as %y's top 12). That is: * * %o4 %y * +----------------+----------------+ * | -12- | -20- | -12- | -20- | * +------(---------+------)---------+ * --hi-- ----low-part---- * * The upper 12 bits of %o4 should be sign-extended to form the * high part of the product (i.e., highpart = %o4 >> 20). */ rd %y, %o5 sll %o4, 12, %o0 ! shift middle bits left 12 srl %o5, 20, %o5 ! shift low bits right 20, zero fill at left or %o5, %o0, %o0 ! construct low part of result retl sra %o4, 20, %o1 ! ... and extract high part of result
