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host-utils: add clrsb32/64 - count leading redundant sign bits 

this patch introduces wrappers for the clrsb builtins,
which count the leading redundant sign bits.

Signed-off-by: Claudio Fontana <claudio.fontana@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
This commit is contained in:
Claudio Fontana 2013-12-17 19:42:35 +00:00 committed by Peter Maydell
parent 8807774235
commit afd3fe4ce5
1 changed files with 32 additions and 0 deletions
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32
include/qemu/host-utils.h
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@ -227,6 +227,38 @@ static inline int cto64(uint64_t val)
return ctz64(~val);
}
/**
* clrsb32 - count leading redundant sign bits in a 32-bit value.
* @val: The value to search
*
* Returns the number of bits following the sign bit that are equal to it.
* No special cases; output range is [0-31].
*/
static inline int clrsb32(uint32_t val)
{
#if QEMU_GNUC_PREREQ(4, 7)
return __builtin_clrsb(val);
#else
return clz32(val ^ ((int32_t)val >> 1)) - 1;
#endif
}
/**
* clrsb64 - count leading redundant sign bits in a 64-bit value.
* @val: The value to search
*
* Returns the number of bits following the sign bit that are equal to it.
* No special cases; output range is [0-63].
*/
static inline int clrsb64(uint64_t val)
{
#if QEMU_GNUC_PREREQ(4, 7)
return __builtin_clrsbll(val);
#else
return clz64(val ^ ((int64_t)val >> 1)) - 1;
#endif
}
/**
* ctpop8 - count the population of one bits in an 8-bit value.
* @val: The value to search