lib: Move mathematic helpers to separate folder

For better maintenance and expansion move the mathematic helpers to the
separate folder.

No functional change intended.

Note, the int_sqrt() is not used as a part of lib, so, moved to regular
obj.

Link: http://lkml.kernel.org/r/20190323172531.80025-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Thierry Reding <thierry.reding@gmail.com>
Cc: Lee Jones <lee.jones@linaro.org>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Ray Jui <rjui@broadcom.com>
[mchehab+samsung@kernel.org: fix broken doc references for div64.c and gcd.c]
  Link: http://lkml.kernel.org/r/734f49bae5d4052b3c25691dfefad59bea2e5843.1555580999.git.mchehab+samsung@kernel.org
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 84 insertions, 0 deletions

diff --git a/lib/math/gcd.c b/lib/math/gcd.c
new file mode 100644
index 000000000000..7948ab27f0a4
--- /dev/null
+++ b/lib/math/gcd.c
@@ -0,0 +1,84 @@
+#include <linux/kernel.h>
+#include <linux/gcd.h>
+#include <linux/export.h>
+
+/*
+ * This implements the binary GCD algorithm. (Often attributed to Stein,
+ * but as Knuth has noted, appears in a first-century Chinese math text.)
+ *
+ * This is faster than the division-based algorithm even on x86, which
+ * has decent hardware division.
+ */
+
+#if !defined(CONFIG_CPU_NO_EFFICIENT_FFS)
+
+/* If __ffs is available, the even/odd algorithm benchmarks slower. */
+
+/**
+ * gcd - calculate and return the greatest common divisor of 2 unsigned longs
+ * @a: first value
+ * @b: second value
+ */
+unsigned long gcd(unsigned long a, unsigned long b)
+{
+        unsigned long r = a | b;
+
+        if (!a || !b)
+                return r;
+
+        b >>= __ffs(b);
+        if (b == 1)
+                return r & -r;
+
+        for (;;) {
+                a >>= __ffs(a);
+                if (a == 1)
+                        return r & -r;
+                if (a == b)
+                        return a << __ffs(r);
+
+                if (a < b)
+                        swap(a, b);
+                a -= b;
+        }
+}
+
+#else
+
+/* If normalization is done by loops, the even/odd algorithm is a win. */
+unsigned long gcd(unsigned long a, unsigned long b)
+{
+        unsigned long r = a | b;
+
+        if (!a || !b)
+                return r;
+
+        /* Isolate lsbit of r */
+        r &= -r;
+
+        while (!(b & r))
+                b >>= 1;
+        if (b == r)
+                return r;
+
+        for (;;) {
+                while (!(a & r))
+                        a >>= 1;
+                if (a == r)
+                        return r;
+                if (a == b)
+                        return a;
+
+                if (a < b)
+                        swap(a, b);
+                a -= b;
+                a >>= 1;
+                if (a & r)
+                        a += b;
+                a >>= 1;
+        }
+}
+
+#endif
+
+EXPORT_SYMBOL_GPL(gcd);