From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751662AbcGRNNt (ORCPT ); Mon, 18 Jul 2016 09:13:49 -0400 Received: from metis.ext.4.pengutronix.de ([92.198.50.35]:42867 "EHLO metis.ext.4.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751136AbcGRNNs (ORCPT ); Mon, 18 Jul 2016 09:13:48 -0400 Message-ID: <1468847611.2994.22.camel@pengutronix.de> Subject: Re: [PATCH v4 09/12] [media] vivid: Local optimization From: Philipp Zabel To: Ricardo Ribalda Delgado Cc: Jonathan Corbet , Mauro Carvalho Chehab , Hans Verkuil , Markus Heiser , Laurent Pinchart , Helen Mae Koike Fornazier , Antti Palosaari , Shuah Khan , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org Date: Mon, 18 Jul 2016 15:13:31 +0200 In-Reply-To: <1468845736-19651-10-git-send-email-ricardo.ribalda@gmail.com> References: <1468845736-19651-1-git-send-email-ricardo.ribalda@gmail.com> <1468845736-19651-10-git-send-email-ricardo.ribalda@gmail.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.12.9-1+b1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 2001:67c:670:100:96de:80ff:fec2:9969 X-SA-Exim-Mail-From: p.zabel@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Ricardo, Am Montag, den 18.07.2016, 14:42 +0200 schrieb Ricardo Ribalda Delgado: > Avoid duplicated data shifts when possible. > > Signed-off-by: Ricardo Ribalda Delgado > --- > drivers/media/common/v4l2-tpg/v4l2-tpg-core.c | 13 +++++++------ > 1 file changed, 7 insertions(+), 6 deletions(-) > > diff --git a/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c b/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c > index a26172575e56..7f284c591f25 100644 > --- a/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c > +++ b/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c > @@ -919,13 +919,14 @@ static void precalculate_color(struct tpg_data *tpg, int k) > color_to_ycbcr(tpg, r, g, b, &y, &cb, &cr); > > if (tpg->real_quantization == V4L2_QUANTIZATION_LIM_RANGE) { > - y = clamp(y, 16 << 4, 235 << 4); > - cb = clamp(cb, 16 << 4, 240 << 4); > - cr = clamp(cr, 16 << 4, 240 << 4); > + y = clamp(y >> 4, 16, 235); > + cb = clamp(cb >> 4, 16, 240); > + cr = clamp(cr >> 4, 16, 240); Since the constant expressions are evaluated at compile time, you are not actually removing shifts. The code generated for precalculate_color by gcc 5.4 even grows by one asr instruction with this patch. > + } else { > + y = clamp(y >> 4, 1, 254); > + cb = clamp(cb >> 4, 1, 254); > + cr = clamp(cr >> 4, 1, 254); > } > - y = clamp(y >> 4, 1, 254); > - cb = clamp(cb >> 4, 1, 254); > - cr = clamp(cr >> 4, 1, 254); > switch (tpg->fourcc) { > case V4L2_PIX_FMT_YUV444: > y >>= 4; regards Philipp