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libbb: move isqrt from factor, use it in diff too

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Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko
2017-04-11 07:34:56 +02:00
parent 10673c44f1
commit 8a134ec680
4 changed files with 63 additions and 29 deletions
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19
coreutils/factor.c
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@@ -44,24 +44,7 @@ typedef unsigned long half_t;
#error Cant find an integer type which is half as wide as ullong
#endif
/* Returns such x that x+1 > sqrt(N) */
static inline half_t isqrt(wide_t N)
{
half_t x;
unsigned shift;
shift = WIDE_BITS - 2;
x = 0;
do {
x = (x << 1) + 1;
if ((wide_t)x * x > (N >> shift))
x--; /* whoops, that +1 was too much */
shift -= 2;
} while ((int)shift >= 0);
return x;
}
static NOINLINE half_t isqrt_odd(wide_t N)
static half_t isqrt_odd(wide_t N)
{
half_t s = isqrt(N);
/* Subtract 1 from even s, odd s won't change: */