From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58799) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Vt1hI-0001By-UB for qemu-devel@nongnu.org; Tue, 17 Dec 2013 15:56:58 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Vt1hG-0002TS-RS for qemu-devel@nongnu.org; Tue, 17 Dec 2013 15:56:56 -0500 Received: from mnementh.archaic.org.uk ([2001:8b0:1d0::1]:43647) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Vt1hG-0002SA-LU for qemu-devel@nongnu.org; Tue, 17 Dec 2013 15:56:54 -0500 From: Peter Maydell Date: Tue, 17 Dec 2013 20:29:06 +0000 Message-Id: <1387312160-12318-49-git-send-email-peter.maydell@linaro.org> In-Reply-To: <1387312160-12318-1-git-send-email-peter.maydell@linaro.org> References: <1387312160-12318-1-git-send-email-peter.maydell@linaro.org> Subject: [Qemu-devel] [PULL 48/62] host-utils: add clrsb32/64 - count leading redundant sign bits List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: Blue Swirl , qemu-devel@nongnu.org, Aurelien Jarno From: Claudio Fontana 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(+) diff --git a/include/qemu/host-utils.h b/include/qemu/host-utils.h index 0f688c1..de85d28 100644 --- a/include/qemu/host-utils.h +++ b/include/qemu/host-utils.h @@ -228,6 +228,38 @@ static inline int cto64(uint64_t 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 */ -- 1.8.5