Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754709AbbLJP3z (ORCPT ); Thu, 10 Dec 2015 10:29:55 -0500 Received: from mail-vk0-f42.google.com ([209.85.213.42]:34468 "EHLO mail-vk0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751387AbbLJP3w (ORCPT ); Thu, 10 Dec 2015 10:29:52 -0500 MIME-Version: 1.0 In-Reply-To: <063D6719AE5E284EB5DD2968C1650D6D1CBEA973@AcuExch.aculab.com> References: <1449712366-31365-1-git-send-email-geyslan@gmail.com> <87twnqjpzy.fsf@saruman.tx.rr.com> <063D6719AE5E284EB5DD2968C1650D6D1CBEA973@AcuExch.aculab.com> Date: Thu, 10 Dec 2015 12:29:51 -0300 Message-ID: Subject: Re: [PATCH] usb: remove redundant conditions From: "Geyslan G. Bem" To: David Laight Cc: Felipe Balbi , "peter.senna@gmail.com" , Greg Kroah-Hartman , Johan Hovold , Robert Baldyga , "linux-usb@vger.kernel.org" , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1541 Lines: 64 2015-12-10 12:17 GMT-03:00 David Laight : > From: Felipe Balbi >> Sent: 10 December 2015 15:14 >> "Geyslan G. Bem" writes: >> >> > This patch removes redundant conditions. >> > >> > - (!A || (A && B)) is the same as (!A || B). >> > - (length && length > 5) can be reduced to a single evaluation. >> > >> > Caught by: cppcheck >> > >> > Signed-off-by: Geyslan G. Bem >> > --- >> >> I guess you didn't get previous comment in time; let's split this per >> driver so different maintainers can pick their parts. > > I also suspect that gcc will optimise out the redundant checks as well. Yes, David. it will. Let's see. void f(int f, int s) { if (!f || (f && s)) printf("branch\n"); } Generates without optimization three comparisons: cmpl $0, -4(%rbp) je .L2 cmpl $0, -4(%rbp) je .L4 cmpl $0, -8(%rbp) je .L4 But with -O2 it generates only two: testl %edi, %edi je .L2 testl %esi, %esi je .L1 Despite that, I think that the patches are welcome since they silence checkpatch and make code clearer. Don't you think? > > David > -- Regards, Geyslan G. Bem hackingbits.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/