| /* $NetBSD: mul.S,v 1.3 1997/07/16 14:37:42 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. All advertising materials mentioning features or use of this software |
| * must display the following acknowledgement: |
| * This product includes software developed by the University of |
| * California, Berkeley and its contributors. |
| * 4. 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 1.3 1997/07/16 14:37:42 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 |
