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author | Crt Mori <cmo@melexis.com> | 2018-01-11 11:19:57 +0100 |
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committer | Jonathan Cameron <Jonathan.Cameron@huawei.com> | 2018-02-04 10:17:21 +0000 |
commit | 47a361634821dc66cefbfa70b9d10a91269d7f7d (patch) | |
tree | ceba4c0edea64792e26e4d1a2363b64e374fa5cd /lib/int_sqrt.c | |
parent | 213451076bd370e55a70ff07f6575b1451ba1a9f (diff) | |
download | op-kernel-dev-47a361634821dc66cefbfa70b9d10a91269d7f7d.zip op-kernel-dev-47a361634821dc66cefbfa70b9d10a91269d7f7d.tar.gz |
lib: Add strongly typed 64bit int_sqrt
There is no option to perform 64bit integer sqrt on 32bit platform.
Added stronger typed int_sqrt64 enables the 64bit calculations to
be performed on 32bit platforms. Using same algorithm as int_sqrt()
with strong typing provides enough precision also on 32bit platforms,
but it sacrifices some performance. In case values are smaller than
ULONG_MAX the standard int_sqrt is used for calculation to maximize the
performance due to more native calculations.
Signed-off-by: Crt Mori <cmo@melexis.com>
Acked-by: Joe Perches <joe@perches.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Diffstat (limited to 'lib/int_sqrt.c')
-rw-r--r-- | lib/int_sqrt.c | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/lib/int_sqrt.c b/lib/int_sqrt.c index e2d3290..14436f4 100644 --- a/lib/int_sqrt.c +++ b/lib/int_sqrt.c @@ -38,3 +38,33 @@ unsigned long int_sqrt(unsigned long x) return y; } EXPORT_SYMBOL(int_sqrt); + +#if BITS_PER_LONG < 64 +/** + * int_sqrt64 - strongly typed int_sqrt function when minimum 64 bit input + * is expected. + * @x: 64bit integer of which to calculate the sqrt + */ +u32 int_sqrt64(u64 x) +{ + u64 b, m, y = 0; + + if (x <= ULONG_MAX) + return int_sqrt((unsigned long) x); + + m = 1ULL << (fls64(x) & ~1ULL); + while (m != 0) { + b = y + m; + y >>= 1; + + if (x >= b) { + x -= b; + y += m; + } + m >>= 2; + } + + return y; +} +EXPORT_SYMBOL(int_sqrt64); +#endif |