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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>
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@ -479,6 +479,15 @@ extern int func_ptr_is_kernel_text(void *ptr);
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unsigned long int_sqrt(unsigned long);
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#if BITS_PER_LONG < 64
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u32 int_sqrt64(u64 x);
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#else
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static inline u32 int_sqrt64(u64 x)
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{
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return (u32)int_sqrt(x);
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}
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#endif
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extern void bust_spinlocks(int yes);
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extern int oops_in_progress; /* If set, an oops, panic(), BUG() or die() is in progress */
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extern int panic_timeout;
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@ -38,3 +38,33 @@ unsigned long int_sqrt(unsigned long x)
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return y;
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}
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EXPORT_SYMBOL(int_sqrt);
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#if BITS_PER_LONG < 64
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/**
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* int_sqrt64 - strongly typed int_sqrt function when minimum 64 bit input
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* is expected.
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* @x: 64bit integer of which to calculate the sqrt
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*/
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u32 int_sqrt64(u64 x)
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{
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u64 b, m, y = 0;
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if (x <= ULONG_MAX)
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return int_sqrt((unsigned long) x);
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m = 1ULL << (fls64(x) & ~1ULL);
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while (m != 0) {
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b = y + m;
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y >>= 1;
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if (x >= b) {
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x -= b;
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y += m;
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}
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m >>= 2;
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}
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return y;
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}
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EXPORT_SYMBOL(int_sqrt64);
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#endif
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