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authorCrt Mori <cmo@melexis.com>2018-01-11 11:19:57 +0100
committerJonathan Cameron <Jonathan.Cameron@huawei.com>2018-02-04 10:17:21 +0000
commit47a361634821dc66cefbfa70b9d10a91269d7f7d (patch)
treeceba4c0edea64792e26e4d1a2363b64e374fa5cd /lib
parent213451076bd370e55a70ff07f6575b1451ba1a9f (diff)
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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')
-rw-r--r--lib/int_sqrt.c30
1 files changed, 30 insertions, 0 deletions
diff --git a/lib/int_sqrt.c b/lib/int_sqrt.c
index e2d329099bf7..14436f4ca6bd 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