From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50737) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V4ElW-0001W1-Ur for qemu-devel@nongnu.org; Tue, 30 Jul 2013 14:35:29 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1V4ElR-0000eD-4s for qemu-devel@nongnu.org; Tue, 30 Jul 2013 14:35:22 -0400 Received: from mail-gh0-x231.google.com ([2607:f8b0:4002:c05::231]:38240) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V4EXV-0004Cx-2q for qemu-devel@nongnu.org; Tue, 30 Jul 2013 14:20:53 -0400 Received: by mail-gh0-f177.google.com with SMTP id f20so1340085ghb.36 for ; Tue, 30 Jul 2013 11:20:52 -0700 (PDT) Sender: Richard Henderson From: Richard Henderson Date: Tue, 30 Jul 2013 08:20:43 -1000 Message-Id: <1375208443-17288-3-git-send-email-rth@twiddle.net> In-Reply-To: <1375208443-17288-1-git-send-email-rth@twiddle.net> References: <1375208443-17288-1-git-send-email-rth@twiddle.net> Subject: [Qemu-devel] [PATCH v2 2/2] qdev: Use clz in print_size List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: vasilis.liaskovitis@profitbricks.com, imammedo@redhat.com, aliguori@us.ibm.com, afaerber@suse.de We can compute a floor log2 value with clz rather than a division loop. Signed-off-by: Richard Henderson --- hw/core/qdev-properties.c | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-) diff --git a/hw/core/qdev-properties.c b/hw/core/qdev-properties.c index d6d10c9..dc8ae69 100644 --- a/hw/core/qdev-properties.c +++ b/hw/core/qdev-properties.c @@ -1172,15 +1172,21 @@ static int parse_size(DeviceState *dev, Property *prop, const char *str) static int print_size(DeviceState *dev, Property *prop, char *dest, size_t len) { - uint64_t *ptr = qdev_get_prop_ptr(dev, prop); - char suffixes[] = {'T', 'G', 'M', 'K', 'B'}; - int i = 0; - uint64_t div; + static const char suffixes[] = { 'B', 'K', 'M', 'G', 'T' }; + uint64_t div, val = *(uint64_t *)qdev_get_prop_ptr(dev, prop); + int i; - for (div = 1ULL << 40; !(*ptr / div) ; div >>= 10) { - i++; + /* Compute floor(log2(val)). */ + i = 64 - clz64(val); + + /* Find the power of 1024 that we'll display as the units. */ + i /= 10; + if (i >= ARRAY_SIZE(suffixes)) { + i = ARRAY_SIZE(suffixes) - 1; } - return snprintf(dest, len, "%0.03f%c", (double)*ptr/div, suffixes[i]); + div = 1ULL << (i * 10); + + return snprintf(dest, len, "%0.03f%c", (double)val/div, suffixes[i]); } PropertyInfo qdev_prop_size = { -- 1.8.3.1