qemu/util/host-utils.c
Richard Henderson ff7a1eb0a1 host-utils: Improve mulu64 and muls64
The new formulation makes better use of add-with-carry type insns
that the host may have.  Use gcc's sign adjustment trick to avoid
having to perform a 128-bit negation.

Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
2013-02-17 14:28:58 +00:00

90 lines
2.5 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 <stdlib.h>
#include <stdint.h>
#include "qemu/host-utils.h"
/* Long integer helpers */
#ifndef CONFIG_INT128
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;
}
#endif /* !CONFIG_INT128 */