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// Inferno utils/8c/div.c
// http://code.google.com/p/inferno-os/source/browse/utils/8c/div.c
//
// Copyright © 1994-1999 Lucent Technologies Inc. All rights reserved.
// Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
// Portions Copyright © 1997-1999 Vita Nuova Limited
// Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
// Portions Copyright © 2004,2006 Bruce Ellis
// Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
// Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
// Portions Copyright © 2009 The Go Authors. All rights reserved.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
#include "gc.h"
/*
* Based on: Granlund, T.; Montgomery, P.L.
* "Division by Invariant Integers using Multiplication".
* SIGPLAN Notices, Vol. 29, June 1994, page 61.
*/
#define TN(n) ((uvlong)1 << (n))
#define T31 TN(31)
#define T32 TN(32)
int
multiplier(uint32 d, int p, uvlong *mp)
{
int l;
uvlong mlo, mhi, tlo, thi;
l = topbit(d - 1) + 1;
mlo = (((TN(l) - d) << 32) / d) + T32;
if(l + p == 64)
mhi = (((TN(l) + 1 - d) << 32) / d) + T32;
else
mhi = (TN(32 + l) + TN(32 + l - p)) / d;
/*assert(mlo < mhi);*/
while(l > 0) {
tlo = mlo >> 1;
thi = mhi >> 1;
if(tlo == thi)
break;
mlo = tlo;
mhi = thi;
l--;
}
*mp = mhi;
return l;
}
int
sdiv(uint32 d, uint32 *mp, int *sp)
{
int s;
uvlong m;
s = multiplier(d, 32 - 1, &m);
*mp = m;
*sp = s;
if(m >= T31)
return 1;
else
return 0;
}
int
udiv(uint32 d, uint32 *mp, int *sp, int *pp)
{
int p, s;
uvlong m;
s = multiplier(d, 32, &m);
p = 0;
if(m >= T32) {
while((d & 1) == 0) {
d >>= 1;
p++;
}
s = multiplier(d, 32 - p, &m);
}
*mp = m;
*pp = p;
if(m >= T32) {
/*assert(p == 0);*/
*sp = s - 1;
return 1;
}
else {
*sp = s;
return 0;
}
}
void
sdivgen(Node *l, Node *r, Node *ax, Node *dx)
{
int a, s;
uint32 m;
vlong c;
c = r->vconst;
if(c < 0)
c = -c;
a = sdiv(c, &m, &s);
//print("a=%d i=%d s=%d m=%ux\n", a, (int32)r->vconst, s, m);
gins(AMOVL, nodconst(m), ax);
gins(AIMULL, l, Z);
gins(AMOVL, l, ax);
if(a)
gins(AADDL, ax, dx);
gins(ASHRL, nodconst(31), ax);
gins(ASARL, nodconst(s), dx);
gins(AADDL, ax, dx);
if(r->vconst < 0)
gins(ANEGL, Z, dx);
}
void
udivgen(Node *l, Node *r, Node *ax, Node *dx)
{
int a, s, t;
uint32 m;
Node nod;
a = udiv(r->vconst, &m, &s, &t);
//print("a=%ud i=%d p=%d s=%d m=%ux\n", a, (int32)r->vconst, t, s, m);
if(t != 0) {
gins(AMOVL, l, ax);
gins(ASHRL, nodconst(t), ax);
gins(AMOVL, nodconst(m), dx);
gins(AMULL, dx, Z);
}
else if(a) {
if(l->op != OREGISTER) {
regalloc(&nod, l, Z);
gins(AMOVL, l, &nod);
l = &nod;
}
gins(AMOVL, nodconst(m), ax);
gins(AMULL, l, Z);
gins(AADDL, l, dx);
gins(ARCRL, nodconst(1), dx);
if(l == &nod)
regfree(l);
}
else {
gins(AMOVL, nodconst(m), ax);
gins(AMULL, l, Z);
}
if(s != 0)
gins(ASHRL, nodconst(s), dx);
}
void
sext(Node *d, Node *s, Node *l)
{
if(s->reg == D_AX && !nodreg(d, Z, D_DX)) {
reg[D_DX]++;
gins(ACDQ, Z, Z);
}
else {
regalloc(d, l, Z);
gins(AMOVL, s, d);
gins(ASARL, nodconst(31), d);
}
}
void
sdiv2(int32 c, int v, Node *l, Node *n)
{
Node nod;
if(v > 0) {
if(v > 1) {
sext(&nod, n, l);
gins(AANDL, nodconst((1 << v) - 1), &nod);
gins(AADDL, &nod, n);
regfree(&nod);
}
else {
gins(ACMPL, n, nodconst(0x80000000));
gins(ASBBL, nodconst(-1), n);
}
gins(ASARL, nodconst(v), n);
}
if(c < 0)
gins(ANEGL, Z, n);
}
void
smod2(int32 c, int v, Node *l, Node *n)
{
Node nod;
if(c == 1) {
zeroregm(n);
return;
}
sext(&nod, n, l);
if(v == 0) {
zeroregm(n);
gins(AXORL, &nod, n);
gins(ASUBL, &nod, n);
}
else if(v > 1) {
gins(AANDL, nodconst((1 << v) - 1), &nod);
gins(AADDL, &nod, n);
gins(AANDL, nodconst((1 << v) - 1), n);
gins(ASUBL, &nod, n);
}
else {
gins(AANDL, nodconst(1), n);
gins(AXORL, &nod, n);
gins(ASUBL, &nod, n);
}
regfree(&nod);
}
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