From patchwork Tue Dec 17 20:29:06 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter Maydell X-Patchwork-Id: 302543 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 9120F2C009B for ; Wed, 18 Dec 2013 09:11:55 +1100 (EST) Received: from localhost ([::1]:35502 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Vt1vo-00086s-1S for incoming@patchwork.ozlabs.org; Tue, 17 Dec 2013 16:11:56 -0500 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 Received: from pm215 by mnementh.archaic.org.uk with local (Exim 4.80) (envelope-from ) id 1Vt1Gd-0003JF-Nb; Tue, 17 Dec 2013 20:29:23 +0000 From: Peter Maydell To: Anthony Liguori Date: Tue, 17 Dec 2013 20:29:06 +0000 Message-Id: <1387312160-12318-49-git-send-email-peter.maydell@linaro.org> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <1387312160-12318-1-git-send-email-peter.maydell@linaro.org> References: <1387312160-12318-1-git-send-email-peter.maydell@linaro.org> X-detected-operating-system: by eggs.gnu.org: Error: Malformed IPv6 address (bad octet value). X-Received-From: 2001:8b0:1d0::1 Cc: Blue Swirl , qemu-devel@nongnu.org, Aurelien Jarno Subject: [Qemu-devel] [PULL 48/62] host-utils: add clrsb32/64 - count leading redundant sign bits X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org 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 */