From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f53.google.com (mail-wm1-f53.google.com [209.85.128.53]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7F9A83D3492 for ; Tue, 20 Jan 2026 22:15:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.53 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768947336; cv=none; b=GDGvN4Y/3kDyNp94eOPpce8MeCk+blPwCdKg7CRwp0IbcGvGF7O+REbd9PrDBK7pWJjpPyqkv1wgkPvvRZzimSIQn2Inm57SZ7QLQrwqA4v9231Ug7wKekBco2IhhArUAgjg+53b4IF3nygST+G8CTqD5nW7hgvFvhKRosKXplA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768947336; c=relaxed/simple; bh=sXzBAhHXFjzE+7Ew7pmu12nDK2dzFTXWtK9hrw9K+No=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=XzB3Dly1L6K+2mhdSgHTbrN1fShDRJ6LpK/9jZxBl6vjJ9ep9kH+0yCojIvuKdJChmQC5BEOr9+QFRvUxzuLu5PGtZgPiZss2g1pBQ79g54RJ3RB5i8lX2tAegGxnWEVuPnQaW9Gt+YuVJGZ0lrzA08s6DdRxWvl3qvd7Q8C6Cg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=Uk3SO3DA; arc=none smtp.client-ip=209.85.128.53 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Uk3SO3DA" Received: by mail-wm1-f53.google.com with SMTP id 5b1f17b1804b1-47ee937ecf2so2380665e9.0 for ; Tue, 20 Jan 2026 14:15:32 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1768947330; x=1769552130; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:subject:cc:to:from:date:from:to:cc:subject:date :message-id:reply-to; bh=QDeVftJLJHUuSKitnBESCg6NtRH3k0fPyxZTFtBUgd0=; b=Uk3SO3DATp1jTmowE0A9EI41d1qjhGSMvaMB5SCLqe4rB0ypxjhrCLVOEty2iQtD6s 2skKc1RVjmb3pkH9o9MevrU4noN+/p/qgPSJaXe7lcQ+sbopnvirGIiclqEFYmtOH5EI O9BuUfWodHsMhfTLjWWpWPCjEfzvwmfpWC8cK+qPWtucaaAEBNnTeIUYY4WcLfFbB0qR BAb16LWWJe/or3Re/GPrSs8zJ9NbiN/Z/UkmTlarxLrebvrFjYw90J8YV6VjQi/GWX1b yuRledp/IpQSJ3gbeczf9Qf9CbUYfd5hGCQwcdFOJqD5uDZy4V2ajSzszgyQScuCdD60 iFiw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1768947330; x=1769552130; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=QDeVftJLJHUuSKitnBESCg6NtRH3k0fPyxZTFtBUgd0=; b=GjjLUm1Hflps74kJB7y00F6bmBzaijTdcE9+qRcEGmN8g0lB/xAomtvsmwc+CvE8uo vnOcKWlupzTuVPAQdz0dOnuwxXZp7z2ZGKAM3EuJcfUMdQddGRsiX6wpMGNSNwaZ9F6K hBO6fvAxRrfDhisGgYag1jUH1/SsNdrcND+FRwtw5E4cNaCMzqqzeaGsDBNmsTPJoZMi t/WYd9J4dQ3+JcDy1tuqP0zomJ3mFcevBK1b6Xa73uAYUpVJgRyE6fvPWq4hx4RYulWz g4C4mvCF5b5fdVLs4+S6habw79XIty72XGCBJlynPzdcge6uJ/E5YCwmBclN+dnz0U3e 0Zww== X-Forwarded-Encrypted: i=1; AJvYcCW2nT3eh+IWE3HZELVhq1ikvdUoLloLtj63qaw5ZQ1dn6xnk1C+vXWsvDZGQbdB2Io0qEOObYG0VFkuWDA=@vger.kernel.org X-Gm-Message-State: AOJu0YxVkaf/uqJ+1/3YlQ1RStpfCKXefQgB1Z75jmswTv2UCEXR9IV1 OjYZ7zjdfJ8B9Z0TxU4c1zrgr3I1hl+nZIm/ZY3YRZg9gyJ8fxEJL6zX X-Gm-Gg: AY/fxX55d+RAEkZuhNx78FOBpilrDSYhYNxCZguhmmlIUujaOMVqswMrt1ZPXlLzjZC 3riZoFi///kbw3xlSnP5B8L2m0hpY5I8TN44otfqZLME19wRXV0MUMI3LTZ32t8yK9EqoG4NItX xqWepEIMkM1it23ejoqGV7l3Ic+JvJrKYDBBOhj4lpj6g4GBnhbGjSISdhx0QvBmtaFIjp+zNBe iFNm38dDTSya8OkpUcRh8SpuCWtm2+zh9IkUlMfM+xppIgHDSQDywxyIPXk5QWq6Xwz1rrRo7q7 o8OB891C4vtLK4YV3syZFKH/gW3vmemlUqFU1DRHTDGmDLJ8zxmDLFsj0DoAewGucR5BKvhkJ2y ePVoIhNldRRGDLeh6qXjYoDPUWDtY6hKu4dzDkl0OiGId+C2TN9hcPkCsQ1teE6vA01cJzg68c5 BnXUa6yrnGiq4gj1LBQIYHrIGPdDJoKo1CPiW8skthfbccvXZgsidO X-Received: by 2002:a05:600c:524f:b0:46f:a2ba:581f with SMTP id 5b1f17b1804b1-4801e685697mr183859665e9.16.1768947330219; Tue, 20 Jan 2026 14:15:30 -0800 (PST) Received: from pumpkin (82-69-66-36.dsl.in-addr.zen.co.uk. [82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-47f428acae8sm324230555e9.4.2026.01.20.14.15.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 20 Jan 2026 14:15:30 -0800 (PST) Date: Tue, 20 Jan 2026 22:15:28 +0000 From: David Laight To: David Desobry Cc: "H. Peter Anvin" , tglx@kernel.org, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86/lib: Fix num_digits() signed overflow for INT_MIN Message-ID: <20260120221528.648bc9a2@pumpkin> In-Reply-To: <6d28349e-9912-474d-a750-71488e2fc976@formalgen.com> References: <20260120094258.41313-1-david.desobry@formalgen.com> <53DB5B87-BA96-44B1-AE1B-9055CB7B9350@zytor.com> <6d28349e-9912-474d-a750-71488e2fc976@formalgen.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Tue, 20 Jan 2026 18:48:54 +0100 David Desobry wrote: > Fair point! I've sent a v2 that replaces the loop with a switch > statement (using GCC ranges). It's faster, Look at the 'crap' that clang generates. And remember that mispredicted branches are expensive and the default is either 'random', 'not taken' or 'backwards branches taken'. It is likely better to have a lot of not-taken branches than a binary tree. David