From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752087AbaK1QCD (ORCPT ); Fri, 28 Nov 2014 11:02:03 -0500 Received: from mail-lb0-f170.google.com ([209.85.217.170]:39342 "EHLO mail-lb0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751971AbaK1QB7 (ORCPT ); Fri, 28 Nov 2014 11:01:59 -0500 From: Rasmus Villemoes To: Andrew Morton , Jan Kara Cc: linux-kernel@vger.kernel.org Subject: [PATCH 5/7] lib: bitmap: Change bitmap_shift_left to take unsigned parameters Date: Fri, 28 Nov 2014 17:01:08 +0100 Message-Id: <1417190476-18066-6-git-send-email-linux@rasmusvillemoes.dk> X-Mailer: git-send-email 2.0.4 In-Reply-To: <1417190476-18066-1-git-send-email-linux@rasmusvillemoes.dk> References: <1417190476-18066-1-git-send-email-linux@rasmusvillemoes.dk> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org gcc can generate slightly better code for stuff like "nbits % BITS_PER_LONG" when it knows nbits is not negative. Since negative size bitmaps or shift amounts don't make sense, change these parameters of bitmap_shift_right to unsigned. If off >= lim (which requires shift >= nbits), k is initialized with a large positive value, but since I've let k continue to be signed, the loop will never run and dst will be zeroed as expected. Inside the loop, k is guaranteed to be non-negative, so the fact that it is promoted to unsigned in the various expressions it appears in is harmless. Also use "shift" and "nbits" consistently for the parameter names. Signed-off-by: Rasmus Villemoes --- include/linux/bitmap.h | 12 ++++++------ lib/bitmap.c | 11 ++++++----- 2 files changed, 12 insertions(+), 11 deletions(-) diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h index 5494adb..fc8abc7 100644 --- a/include/linux/bitmap.h +++ b/include/linux/bitmap.h @@ -96,8 +96,8 @@ extern void __bitmap_complement(unsigned long *dst, const unsigned long *src, unsigned int nbits); extern void __bitmap_shift_right(unsigned long *dst, const unsigned long *src, unsigned int shift, unsigned int nbits); -extern void __bitmap_shift_left(unsigned long *dst, - const unsigned long *src, int shift, int bits); +extern void __bitmap_shift_left(unsigned long *dst, const unsigned long *src, + unsigned int shift, unsigned int nbits); extern int __bitmap_and(unsigned long *dst, const unsigned long *bitmap1, const unsigned long *bitmap2, unsigned int nbits); extern void __bitmap_or(unsigned long *dst, const unsigned long *bitmap1, @@ -289,13 +289,13 @@ static inline void bitmap_shift_right(unsigned long *dst, const unsigned long *s __bitmap_shift_right(dst, src, shift, nbits); } -static inline void bitmap_shift_left(unsigned long *dst, - const unsigned long *src, int n, int nbits) +static inline void bitmap_shift_left(unsigned long *dst, const unsigned long *src, + unsigned int shift, unsigned int nbits) { if (small_const_nbits(nbits)) - *dst = (*src << n) & BITMAP_LAST_WORD_MASK(nbits); + *dst = (*src << shift) & BITMAP_LAST_WORD_MASK(nbits); else - __bitmap_shift_left(dst, src, n, nbits); + __bitmap_shift_left(dst, src, shift, nbits); } static inline int bitmap_parse(const char *buf, unsigned int buflen, diff --git a/lib/bitmap.c b/lib/bitmap.c index 0d78c96..5edd71b 100644 --- a/lib/bitmap.c +++ b/lib/bitmap.c @@ -146,18 +146,19 @@ EXPORT_SYMBOL(__bitmap_shift_right); * @dst : destination bitmap * @src : source bitmap * @shift : shift by this many bits - * @bits : bitmap size, in bits + * @nbits : bitmap size, in bits * * Shifting left (multiplying) means moving bits in the LS -> MS * direction. Zeros are fed into the vacated LS bit positions * and those MS bits shifted off the top are lost. */ -void __bitmap_shift_left(unsigned long *dst, - const unsigned long *src, int shift, int bits) +void __bitmap_shift_left(unsigned long *dst, const unsigned long *src, + unsigned int shift, unsigned int nbits) { - int k, lim = BITS_TO_LONGS(bits), left = bits % BITS_PER_LONG; - int off = shift/BITS_PER_LONG, rem = shift % BITS_PER_LONG; + int k; + unsigned int lim = BITS_TO_LONGS(nbits), left = nbits % BITS_PER_LONG; + unsigned int off = shift/BITS_PER_LONG, rem = shift % BITS_PER_LONG; for (k = lim - off - 1; k >= 0; --k) { unsigned long upper, lower; -- 2.0.4