qemu/util/host-utils.c
Jose Ricardo Ziviani f539fbe337 host-utils: Implement unsigned quadword left/right shift and unit tests
Implements 128-bit left shift and right shift as well as their
testcases. By design, shift silently mods by 128, so the caller is
responsible to assert the shift range if necessary.

Left shift sets the overflow flag if any non-zero digit is shifted out.

Examples:
 ulshift(&low, &high, 250, &overflow);
 equivalent: n << 122

 urshift(&low, &high, -2);
 equivalent: n << 126

Signed-off-by: Jose Ricardo Ziviani <joserz@linux.vnet.ibm.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[dwg: Added test-shift128 to .gitignore]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
2017-01-31 10:10:14 +11:00

228 lines
5.9 KiB
C

/*
* Utility compute operations used by translated code.
*
* Copyright (c) 2003 Fabrice Bellard
* Copyright (c) 2007 Aurelien Jarno
*
* 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 "qemu/osdep.h"
#include "qemu/host-utils.h"
#ifndef CONFIG_INT128
/* Long integer helpers */
static inline void mul64(uint64_t *plow, uint64_t *phigh,
uint64_t a, uint64_t b)
{
typedef union {
uint64_t ll;
struct {
#ifdef HOST_WORDS_BIGENDIAN
uint32_t high, low;
#else
uint32_t low, high;
#endif
} l;
} LL;
LL rl, rm, rn, rh, a0, b0;
uint64_t c;
a0.ll = a;
b0.ll = b;
rl.ll = (uint64_t)a0.l.low * b0.l.low;
rm.ll = (uint64_t)a0.l.low * b0.l.high;
rn.ll = (uint64_t)a0.l.high * b0.l.low;
rh.ll = (uint64_t)a0.l.high * b0.l.high;
c = (uint64_t)rl.l.high + rm.l.low + rn.l.low;
rl.l.high = c;
c >>= 32;
c = c + rm.l.high + rn.l.high + rh.l.low;
rh.l.low = c;
rh.l.high += (uint32_t)(c >> 32);
*plow = rl.ll;
*phigh = rh.ll;
}
/* Unsigned 64x64 -> 128 multiplication */
void mulu64 (uint64_t *plow, uint64_t *phigh, uint64_t a, uint64_t b)
{
mul64(plow, phigh, a, b);
}
/* Signed 64x64 -> 128 multiplication */
void muls64 (uint64_t *plow, uint64_t *phigh, int64_t a, int64_t b)
{
uint64_t rh;
mul64(plow, &rh, a, b);
/* Adjust for signs. */
if (b < 0) {
rh -= a;
}
if (a < 0) {
rh -= b;
}
*phigh = rh;
}
/* Unsigned 128x64 division. Returns 1 if overflow (divide by zero or */
/* quotient exceeds 64 bits). Otherwise returns quotient via plow and */
/* remainder via phigh. */
int divu128(uint64_t *plow, uint64_t *phigh, uint64_t divisor)
{
uint64_t dhi = *phigh;
uint64_t dlo = *plow;
unsigned i;
uint64_t carry = 0;
if (divisor == 0) {
return 1;
} else if (dhi == 0) {
*plow = dlo / divisor;
*phigh = dlo % divisor;
return 0;
} else if (dhi > divisor) {
return 1;
} else {
for (i = 0; i < 64; i++) {
carry = dhi >> 63;
dhi = (dhi << 1) | (dlo >> 63);
if (carry || (dhi >= divisor)) {
dhi -= divisor;
carry = 1;
} else {
carry = 0;
}
dlo = (dlo << 1) | carry;
}
*plow = dlo;
*phigh = dhi;
return 0;
}
}
int divs128(int64_t *plow, int64_t *phigh, int64_t divisor)
{
int sgn_dvdnd = *phigh < 0;
int sgn_divsr = divisor < 0;
int overflow = 0;
if (sgn_dvdnd) {
*plow = ~(*plow);
*phigh = ~(*phigh);
if (*plow == (int64_t)-1) {
*plow = 0;
(*phigh)++;
} else {
(*plow)++;
}
}
if (sgn_divsr) {
divisor = 0 - divisor;
}
overflow = divu128((uint64_t *)plow, (uint64_t *)phigh, (uint64_t)divisor);
if (sgn_dvdnd ^ sgn_divsr) {
*plow = 0 - *plow;
}
if (!overflow) {
if ((*plow < 0) ^ (sgn_dvdnd ^ sgn_divsr)) {
overflow = 1;
}
}
return overflow;
}
#endif
/**
* urshift - 128-bit Unsigned Right Shift.
* @plow: in/out - lower 64-bit integer.
* @phigh: in/out - higher 64-bit integer.
* @shift: in - bytes to shift, between 0 and 127.
*
* Result is zero-extended and stored in plow/phigh, which are
* input/output variables. Shift values outside the range will
* be mod to 128. In other words, the caller is responsible to
* verify/assert both the shift range and plow/phigh pointers.
*/
void urshift(uint64_t *plow, uint64_t *phigh, int32_t shift)
{
shift &= 127;
if (shift == 0) {
return;
}
uint64_t h = *phigh >> (shift & 63);
if (shift >= 64) {
*plow = h;
*phigh = 0;
} else {
*plow = (*plow >> (shift & 63)) | (*phigh << (64 - (shift & 63)));
*phigh = h;
}
}
/**
* ulshift - 128-bit Unsigned Left Shift.
* @plow: in/out - lower 64-bit integer.
* @phigh: in/out - higher 64-bit integer.
* @shift: in - bytes to shift, between 0 and 127.
* @overflow: out - true if any 1-bit is shifted out.
*
* Result is zero-extended and stored in plow/phigh, which are
* input/output variables. Shift values outside the range will
* be mod to 128. In other words, the caller is responsible to
* verify/assert both the shift range and plow/phigh pointers.
*/
void ulshift(uint64_t *plow, uint64_t *phigh, int32_t shift, bool *overflow)
{
uint64_t low = *plow;
uint64_t high = *phigh;
shift &= 127;
if (shift == 0) {
return;
}
/* check if any bit will be shifted out */
urshift(&low, &high, 128 - shift);
if (low | high) {
*overflow = true;
}
if (shift >= 64) {
*phigh = *plow << (shift & 63);
*plow = 0;
} else {
*phigh = (*plow >> (64 - (shift & 63))) | (*phigh << (shift & 63));
*plow = *plow << shift;
}
}