From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751797AbaK1QBh (ORCPT ); Fri, 28 Nov 2014 11:01:37 -0500 Received: from mail-la0-f48.google.com ([209.85.215.48]:63784 "EHLO mail-la0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751708AbaK1QBg (ORCPT ); Fri, 28 Nov 2014 11:01:36 -0500 From: Rasmus Villemoes To: Andrew Morton , Jan Kara Cc: linux-kernel@vger.kernel.org Subject: [PATCH 0/7] lib: bitmap: Simplify bitmap_shift_{left,right} Date: Fri, 28 Nov 2014 17:01:03 +0100 Message-Id: <1417190476-18066-1-git-send-email-linux@rasmusvillemoes.dk> X-Mailer: git-send-email 2.0.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org I've previously changed the nbits parameter of most bitmap_* functions to unsigned; now it is bitmap_shift_{left,right}'s turn. This alone saves some .text, but while at it I found that there were a few other things one could do. The end result of these seven patches is $ scripts/bloat-o-meter /tmp/bitmap.o.{old,new} add/remove: 0/0 grow/shrink: 0/2 up/down: 0/-328 (-328) function old new delta __bitmap_shift_right 384 226 -158 __bitmap_shift_left 306 136 -170 and less importantly also a smaller stack footprint $ stack-o-meter.pl master bitmap file function old new delta lib/bitmap.o __bitmap_shift_right 24 8 -16 lib/bitmap.o __bitmap_shift_left 24 0 -24 For each pair of 0 <= shift <= nbits <= 256 I've tested the end result with a few randomly filled src buffers (including garbage beyond nbits), in each case verifying that the shift {left,right}-most bits of dst are zero and the remaining nbits-shift bits correspond to src, so I'm fairly confident I didn't screw up. That hasn't stopped me from being wrong before, though. Rasmus Villemoes (7): lib: bitmap: Change bitmap_shift_right to take unsigned parameters lib: bitmap: Eliminate branch in __bitmap_shift_right lib: bitmap: Remove redundant code from __bitmap_shift_right lib: bitmap: Yet another simplification in __bitmap_shift_right lib: bitmap: Change bitmap_shift_left to take unsigned parameters lib: bitmap: Eliminate branch in __bitmap_shift_left lib: bitmap: Remove redundant code from __bitmap_shift_left include/linux/bitmap.h | 24 ++++++++++++------------ lib/bitmap.c | 47 ++++++++++++++++++++--------------------------- 2 files changed, 32 insertions(+), 39 deletions(-) -- 2.0.4