From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: linearize bug? Date: Sat, 27 Aug 2011 16:03:54 -0400 Message-ID: <4E594DAA.8060401@garzik.org> References: <4E588EB8.80808@garzik.org> <201108271334.17659.kdudka@redhat.com> <4E590F22.6030800@garzik.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-qw0-f46.google.com ([209.85.216.46]:41487 "EHLO mail-qw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751511Ab1H0UD5 (ORCPT ); Sat, 27 Aug 2011 16:03:57 -0400 Received: by qwk3 with SMTP id 3so2613194qwk.19 for ; Sat, 27 Aug 2011 13:03:57 -0700 (PDT) In-Reply-To: Sender: linux-sparse-owner@vger.kernel.org List-Id: linux-sparse@vger.kernel.org To: Linus Torvalds Cc: Kamil Dudka , Sparse Mailing-list , Pekka J Enberg On 08/27/2011 11:53 AM, Linus Torvalds wrote: > On Sat, Aug 27, 2011 at 8:37 AM, Jeff Garzik wrote: >> >> On our point of view, we probably prefer to simply turn off as many >> transformations as possible. They just waste time, when an optimizing LLVM >> backend is going to perform the same transformations anyway. > > I disagree - mainly because I don't think we're interested in the back > end, are we? > > If we were doing LLVM hacking, then I'd agree. But as it is, we're > supposed to improve sparse, not LLVM, so we should make sure that the > _sparse_ output makes sense, and LLVM is just a code generator, no? No idea Pekka's interest... In general, my own decade-long goal has been to be able to play with a kernel compiler other than gcc. That's why I wrote compile-i386 so long ago, that's why the kernel got a bunch of LLVM-related bug fixes and C cleanups, that's why I wrote the original sparse LLVM backend[1], and why I'm working on Pekka's now. So I'm definitely more interested in the backend side of things, and tend to see simplifications and optimizations performed on the linearized form as wasted work. sparse makes a great C front-end to a compiler. Obviously that's not the only PoV or use case of sparse, and is arguably a crazy, unattainable goal in general... :) Jeff [1] https://patchwork.kernel.org/patch/19923/