From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 84490 invoked by alias); 27 Jul 2017 08:29:28 -0000 Mailing-List: contact newlib-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: newlib-owner@sourceware.org Received: (qmail 84478 invoked by uid 89); 27 Jul 2017 08:29:27 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-24.6 required=5.0 tests=AWL,BAYES_00,FREEMAIL_FROM,GIT_PATCH_0,GIT_PATCH_1,GIT_PATCH_2,GIT_PATCH_3,RCVD_IN_DNSWL_NONE,RCVD_IN_SORBS_SPAM,SPF_PASS autolearn=ham version=3.3.2 spammy=Hx-spam-relays-external:209.85.217.193, H*RU:209.85.217.193 X-HELO: mail-ua0-f193.google.com Received: from mail-ua0-f193.google.com (HELO mail-ua0-f193.google.com) (209.85.217.193) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Thu, 27 Jul 2017 08:29:26 +0000 Received: by mail-ua0-f193.google.com with SMTP id w45so16103803uac.3 for ; Thu, 27 Jul 2017 01:29:26 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:sender:in-reply-to:references:from :date:message-id:subject:to:cc; bh=wo7wgJGfWGFpqjsT0Of42C5tKaf2d4ZQ+Xlr+T8zmog=; b=jzNHDvQTIXedGIRF3NhOyeud/+UEED9nvVkidJeYwKDFTbHWxF5l2gy9PaQKKZZuHe bdDHCkip0bWLtSq2oz8DEHv+k/st2by88rhkgkF0hK8SJoHfzPsYzNC74SZgyRf6/uCp HrDG9Brm4UImXtJkRUlB3pg5Ij+qTR2MiFOsv9G7JSRcng6a953DpV0/Za5UAmHtFyy6 7purnWNUTxoHc+JuRrZQl4nv/A++j4I82SIF0SAvED/Ld+gD0mU/qHVcHwxExH9kZkpn jIgb1UPVDflFJylsHFUBJ5XpipaF9U4nvsRBlsjy7kTdr0u6r5UgagmCRQ5pKpiF7oEp VKLA== X-Gm-Message-State: AIVw111892q2KNwHxrJNy3wJfJTF+VS151LCF4PtV3ijHN6+7OflWeor LtiI1X8Ni+E0Lrh/DUAPFMraqtP1Tg== X-Received: by 10.31.218.133 with SMTP id r127mr1953060vkg.104.1501144164620; Thu, 27 Jul 2017 01:29:24 -0700 (PDT) MIME-Version: 1.0 Received: by 10.31.96.72 with HTTP; Thu, 27 Jul 2017 01:29:04 -0700 (PDT) In-Reply-To: <20170727080624.24818-1-sebastian.huber@embedded-brains.de> References: <20170727080624.24818-1-sebastian.huber@embedded-brains.de> From: Kito Cheng Date: Thu, 27 Jul 2017 08:29:00 -0000 Message-ID: Subject: Re: [PATCH] Workaround for ffs() on LP64 targets To: Sebastian Huber Cc: newlib@sourceware.org Content-Type: text/plain; charset="UTF-8" X-IsSubscribed: yes X-SW-Source: 2017/txt/msg00666.txt.bz2 it's will make aarch64 gen worse code (compare to __builtin_ffs version) since aarch64 have clz, but I don't have better idea too... On Thu, Jul 27, 2017 at 4:06 PM, Sebastian Huber wrote: > Signed-off-by: Sebastian Huber > --- > newlib/libc/misc/ffs.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/newlib/libc/misc/ffs.c b/newlib/libc/misc/ffs.c > index ba5700920..a09cbd3bb 100644 > --- a/newlib/libc/misc/ffs.c > +++ b/newlib/libc/misc/ffs.c > @@ -31,6 +31,17 @@ No supporting OS subroutines are required. */ > int > ffs(int i) > { > +#ifdef __LP64__ > + /* GCC would expand the __builtin_ffs() to ffs() in this case */ > + int bit; > + > + if (i == 0) > + return (0); > + for (bit = 1; !(i & 1); bit++) > + i = (unsigned int)i >> 1; > + return (bit); > +#else > > return (__builtin_ffs(i)); > +#endif > } > -- > 2.12.3 >