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[POWERPC] Optimize fls64() on 64-bit processors

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64-bit powerpc processors can find the leftmost 1 bit in a 64-bit
doubleword in one instruction, so use that rather than using the
generic fls64(), which does two 32-bit fls() calls.

Signed-off-by: Paul Mackerras <paulus@samba.org>
This commit is contained in:
Paul Mackerras 2008-04-18 14:26:08 +10:00
parent 945feb174b
commit 9f264be610
1 changed files with 17 additions and 0 deletions
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17
include/asm-powerpc/bitops.h
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@ -312,7 +312,24 @@ static __inline__ int fls(unsigned int x)
asm ("cntlzw %0,%1" : "=r" (lz) : "r" (x));
return 32 - lz;
}
/*
* 64-bit can do this using one cntlzd (count leading zeroes doubleword)
* instruction; for 32-bit we use the generic version, which does two
* 32-bit fls calls.
*/
#ifdef __powerpc64__
static __inline__ int fls64(__u64 x)
{
int lz;
asm ("cntlzd %0,%1" : "=r" (lz) : "r" (x));
return 64 - lz;
}
#else
#include <asm-generic/bitops/fls64.h>
#endif /* __powerpc64__ */
#include <asm-generic/bitops/hweight.h>
#include <asm-generic/bitops/find.h>