b6cbf7203b
This patch imports the unmodified current version of NetBSD libc. The NetBSD includes are in /nbsd_include, while the libc code itself is split between lib/nbsd_libc and common/lib/libc.
190 lines
6.3 KiB
ArmAsm
190 lines
6.3 KiB
ArmAsm
/* $NetBSD: umul.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: umul.s,v 1.4 92/06/25 13:24:05 torek Exp
|
|
*/
|
|
|
|
#include <machine/asm.h>
|
|
#if defined(LIBC_SCCS) && !defined(lint)
|
|
#if 0
|
|
.asciz "@(#)umul.s 8.1 (Berkeley) 6/4/93"
|
|
#else
|
|
RCSID("$NetBSD: umul.S,v 1.1 2005/12/20 19:28:50 christos Exp $")
|
|
#endif
|
|
#endif /* LIBC_SCCS and not lint */
|
|
|
|
/*
|
|
* Unsigned multiply. 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. Short
|
|
* multiplies require 25 instruction cycles, and long ones require
|
|
* 45 instruction cycles.
|
|
*
|
|
* On return, overflow has occurred (%o1 is not zero) if and only if
|
|
* the Z condition code is clear, allowing, e.g., the following:
|
|
*
|
|
* call .umul
|
|
* nop
|
|
* bnz overflow (or tnz)
|
|
*/
|
|
|
|
FUNC(.umul)
|
|
or %o0, %o1, %o4
|
|
mov %o0, %y ! multiplier -> Y
|
|
andncc %o4, 0xfff, %g0 ! test bits 12..31 of *both* args
|
|
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
|
|
|
|
|
|
/*
|
|
* Normally, with the shift-and-add approach, if both numbers are
|
|
* positive you get the correct result. WIth 32-bit two's-complement
|
|
* numbers, -x is represented as
|
|
*
|
|
* x 32
|
|
* ( 2 - ------ ) mod 2 * 2
|
|
* 32
|
|
* 2
|
|
*
|
|
* (the `mod 2' subtracts 1 from 1.bbbb). To avoid lots of 2^32s,
|
|
* we can treat this as if the radix point were just to the left
|
|
* of the sign bit (multiply by 2^32), and get
|
|
*
|
|
* -x = (2 - x) mod 2
|
|
*
|
|
* Then, ignoring the `mod 2's for convenience:
|
|
*
|
|
* x * y = xy
|
|
* -x * y = 2y - xy
|
|
* x * -y = 2x - xy
|
|
* -x * -y = 4 - 2x - 2y + xy
|
|
*
|
|
* For signed multiplies, we subtract (x << 32) from the partial
|
|
* product to fix this problem for negative multipliers (see mul.s).
|
|
* Because of the way the shift into the partial product is calculated
|
|
* (N xor V), this term is automatically removed for the multiplicand,
|
|
* so we don't have to adjust.
|
|
*
|
|
* But for unsigned multiplies, the high order bit wasn't a sign bit,
|
|
* and the correction is wrong. So for unsigned multiplies where the
|
|
* high order bit is one, we end up with xy - (y << 32). To fix it
|
|
* we add y << 32.
|
|
*/
|
|
tst %o1
|
|
bl,a 1f ! if %o1 < 0 (high order bit = 1),
|
|
add %o4, %o0, %o4 ! %o4 += %o0 (add y to upper half)
|
|
1: rd %y, %o0 ! get lower half of product
|
|
retl
|
|
addcc %o4, %g0, %o1 ! put upper half in place and set Z for %o1==0
|
|
|
|
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),
|
|
* and overflow is impossible (the answer is at most 24 bits long).
|
|
*/
|
|
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 result; %y has
|
|
* the bottom 12 (as %y's top 12). That is:
|
|
*
|
|
* %o4 %y
|
|
* +----------------+----------------+
|
|
* | -12- | -20- | -12- | -20- |
|
|
* +------(---------+------)---------+
|
|
* -----result-----
|
|
*
|
|
* The 12 bits of %o4 left of the `result' area are all zero;
|
|
* in fact, all top 20 bits of %o4 are zero.
|
|
*/
|
|
|
|
rd %y, %o5
|
|
sll %o4, 12, %o0 ! shift middle bits left 12
|
|
srl %o5, 20, %o5 ! shift low bits right 20
|
|
or %o5, %o0, %o0
|
|
retl
|
|
addcc %g0, %g0, %o1 ! %o1 = zero, and set Z
|