qemu/host-utils.c
ths 67fc07d3fb Fix overflow when multiplying two large positive numbers.
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@3429 c046a42c-6fe2-441c-8c8c-71466251a162
2007-10-23 23:22:54 +00:00

78 lines
2.5 KiB
C

/*
* Utility compute operations used by translated code.
*
* 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 "vl.h"
/* Signed 64x64 -> 128 multiplication */
void muls64(int64_t *phigh, int64_t *plow, int64_t a, int64_t b)
{
#if defined(__x86_64__)
__asm__ ("imul %0\n\t"
: "=d" (*phigh), "=a" (*plow)
: "a" (a), "0" (b)
);
#else
int64_t ph;
uint64_t pm1, pm2, pl;
pl = (uint64_t)((uint32_t)a) * (uint64_t)((uint32_t)b);
pm1 = (a >> 32) * (uint32_t)b;
pm2 = (uint32_t)a * (b >> 32);
ph = (a >> 32) * (b >> 32);
ph += (int64_t)pm1 >> 32;
ph += (int64_t)pm2 >> 32;
pm1 = (uint64_t)((uint32_t)pm1) + (uint64_t)((uint32_t)pm2) + (pl >> 32);
*phigh = ph + ((int64_t)pm1 >> 32);
*plow = (pm1 << 32) + (uint32_t)pl;
#endif
}
/* Unsigned 64x64 -> 128 multiplication */
void mulu64(uint64_t *phigh, uint64_t *plow, uint64_t a, uint64_t b)
{
#if defined(__x86_64__)
__asm__ ("mul %0\n\t"
: "=d" (*phigh), "=a" (*plow)
: "a" (a), "0" (b)
);
#else
uint64_t ph, pm1, pm2, pl;
pl = (uint64_t)((uint32_t)a) * (uint64_t)((uint32_t)b);
pm1 = (a >> 32) * (uint32_t)b;
pm2 = (uint32_t)a * (b >> 32);
ph = (a >> 32) * (b >> 32);
ph += pm1 >> 32;
ph += pm2 >> 32;
pm1 = (uint64_t)((uint32_t)pm1) + (uint64_t)((uint32_t)pm2) + (pl >> 32);
*phigh = ph + (pm1 >> 32);
*plow = (pm1 << 32) + (uint32_t)pl;
#endif
}