From afd3fe4ce56e6fb0d0384ddb8e3c4fac01935c37 Mon Sep 17 00:00:00 2001 From: Claudio Fontana Date: Tue, 17 Dec 2013 19:42:35 +0000 Subject: 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 Signed-off-by: Peter Maydell Reviewed-by: Richard Henderson --- include/qemu/host-utils.h | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) (limited to 'include') diff --git a/include/qemu/host-utils.h b/include/qemu/host-utils.h index 0f688c1c00..de85d282d0 100644 --- a/include/qemu/host-utils.h +++ b/include/qemu/host-utils.h @@ -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 -- cgit v1.2.1