motorhead/qemu
1
0
Fork 0
mirror of https://github.com/Motorhead1991/qemu.git synced 2025-08-02 07:13:54 -06:00
Code Issues Projects Releases Packages Wiki Activity Actions

host-utils: move checks out of divu128/divs128

Browse source 
In preparation for changing the divu128/divs128 implementations
to allow for quotients larger than 64 bits, move the div-by-zero
and overflow checks to the callers.

Signed-off-by: Luis Pires <luis.pires@eldorado.org.br>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20211025191154.350831-2-luis.pires@eldorado.org.br>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Luis Pires 2021-10-25 16:11:36 -03:00 • committed by Richard Henderson
parent 1c46937358
commit 9276a31c34
4 changed files with 42 additions and 51 deletions
Download patch file Download diff file Expand all files Collapse all files

40
util/host-utils.c
View file

@ -86,24 +86,23 @@ void muls64 (uint64_t *plow, uint64_t *phigh, int64_t a, int64_t 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)
/*
* Unsigned 128-by-64 division. Returns quotient via plow and
* remainder via phigh.
* The result must fit in 64 bits (plow) - otherwise, the result
* is undefined.
* This function will cause a division by zero if passed a zero divisor.
*/
void 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) {
if (divisor == 0 || dhi == 0) {
*plow = dlo / divisor;
*phigh = dlo % divisor;
return 0;
} else if (dhi >= divisor) {
return 1;
} else {
for (i = 0; i < 64; i++) {
@ -120,15 +119,20 @@ int divu128(uint64_t *plow, uint64_t *phigh, uint64_t divisor)
*plow = dlo;
*phigh = dhi;
return 0;
}
}
int divs128(int64_t *plow, int64_t *phigh, int64_t divisor)
/*
* Signed 128-by-64 division. Returns quotient via plow and
* remainder via phigh.
* The result must fit in 64 bits (plow) - otherwise, the result
* is undefined.
* This function will cause a division by zero if passed a zero divisor.
*/
void 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);
@ -145,19 +149,11 @@ int divs128(int64_t *plow, int64_t *phigh, int64_t divisor)
divisor = 0 - divisor;
}
overflow = divu128((uint64_t *)plow, (uint64_t *)phigh, (uint64_t)divisor);
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