lib: Add strongly typed 64bit int_sqrt
Subsystems (2)
PATCH v11 1/3 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.
Signed-off-by Crt Mori <[email protected]>
--- include/linux/kernel.h | 9 +++++++++ lib/int_sqrt.c | 31 +++++++++++++++++++++++++++++++ 2 files changed, 40 insertions(+)
include/linux/kernel.h +9 -0
@@ -460,6 +460,15 @@ extern int func_ptr_is_kernel_text(void *ptr);unsigned long int_sqrt (unsigned long ); +#if BITS_PER_LONG <64 +u32 int_sqrt64 (u64 x); +#else +static inline u32 int_sqrt64 (u64 x) +{ +return (u32 )int_sqrt (x); +} +#endif +extern void bust_spinlocks (int yes);extern int oops_in_progress;/* If set, an oops, panic(), BUG() or die() is in progress */ extern int panic_timeout;
lib/int_sqrt.c +31 -0
@@ -7,6 +7,7 @@#include <linux/kernel.h> #include <linux/export.h> +#include <linux/bitops.h> /** * int_sqrt - rough approximation to sqrt
@@ -36,3 +37,33 @@ 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 <=1 ) +return 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
Signature · 1 line
2.15.0