From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.devel Subject: Re: Shrinking the C core Date: Sun, 20 Aug 2023 22:07:50 +0300 Message-ID: <837cppwn09.fsf@gnu.org> References: <20230809094655.793FC18A4654@snark.thyrsus.com> <87y1if8j8t.fsf@linux-m68k.org> <87y1ifi9fv.fsf@dataswamp.org> <87zg2uqdmv.fsf@localhost> <87edk3gbh3.fsf@dataswamp.org> <87jztvnuyb.fsf@localhost> <875y5bdutt.fsf@dataswamp.org> <87y1i6e1uh.fsf@localhost> <874jkub40o.fsf@dataswamp.org> <87jztqdw2l.fsf@localhost> <87msym9i4r.fsf@dataswamp.org> <877cpp914t.fsf@localhost> <83fs4dwwdo.fsf@gnu.org> <874jkt90a5.fsf@localhost> <87y1i57jqi.fsf@localhost> <87pm3h7h8k.fsf@localhost> Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="37817"; mail-complaints-to="usenet@ciao.gmane.io" Cc: yantar92@posteo.net, incal@dataswamp.org, emacs-devel@gnu.org To: "Alfred M. Szmidt" , Andrea Corallo Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Sun Aug 20 21:08:12 2023 Return-path: Envelope-to: ged-emacs-devel@m.gmane-mx.org Original-Received: from lists.gnu.org ([209.51.188.17]) by ciao.gmane.io with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1qXnmW-0009cx-3H for ged-emacs-devel@m.gmane-mx.org; Sun, 20 Aug 2023 21:08:12 +0200 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qXnlz-0007uK-Gu; Sun, 20 Aug 2023 15:07:39 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qXnlx-0007u7-9o for emacs-devel@gnu.org; Sun, 20 Aug 2023 15:07:37 -0400 Original-Received: from fencepost.gnu.org ([2001:470:142:3::e]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qXnlv-0005Sp-2L; Sun, 20 Aug 2023 15:07:35 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=gnu.org; s=fencepost-gnu-org; h=References:Subject:In-Reply-To:To:From:Date: mime-version; bh=3aiWsNLTGSAPdk170vFk3N6Zy3CjzoTHWUZFyqVfqf8=; b=TDvhL7uVP8Pu 0Xn5zL13kFtQvXsbWBZ1sUvnN1jW8z9oxv7/R0ylYM96W0e5tptfb+H85ziX14lptWvZkMoH0I1jx K8YLsgvSpvEaFwilwL81vfAewDOlMinu9ddmIB44bzotP2diCyh8/rQtyBgKUjQtHpmrZbzeAtCYr daEMhbxbpy7NL/V53odccxzV2OjBg7nbxfG5rxXl4wc0iTJs+i8BwXIeji2BotGCDUBoXmnFQcDEF StM7XgjGdh2YfbHVK20i3jXBGWU1glSpZw/teIS9JPM1QmBfcuA63HObnAtaPhNnbpl1gCdGhx9EY dLQX5RgGb2WcjCQJn1GOew==; In-Reply-To: (ams@gnu.org) X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Original-Sender: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Xref: news.gmane.io gmane.emacs.devel:308985 Archived-At: > From: "Alfred M. Szmidt" > Cc: eliz@gnu.org, incal@dataswamp.org, emacs-devel@gnu.org > Date: Sun, 20 Aug 2023 14:54:46 -0400 > > > "Alfred M. Szmidt" writes: > > > Not really. Native compilation already uses GCC. At least on the byte > > code instructions and, separately, in subr code. > > There is more than just GCC vs byte code VM in it. > > > > It is not about native compilation! It is about what OPTIMIZATIONS > > can be done to the actual code flow. Just using GCC doesn't do ANY > > optimizations to how the Lisp code is optimized or how its flow is > > changed due to optimizations! > > Then, what does GCC do? AFAIK, GCC JIT takes the Elisp byte code, > transforms it into JIT pseudocode, and optimizes the actual code flow. > > What does GCC do _WHERE_? What backend? What language? You're > speaking in such broad terms that it makes it impossible to continue > this discussion. I don't know how the native compilation works, but > no matter what you feed to GCC it cannot do magic and any optimization > should be done on what the Emacs compiler does. > > For example, when I write > > (when (> x y) (when (> x y) x)) > > I expect GCC JIT to throw away the duplicate comparison. > > Why do you expect that? Why do you think it is duplicate? Where are > the guarantees that > or WHEN don't have side-effects? Andrea will correct me if I'm wrong, but AFAIU Ihor is correct: native compilation in Emacs emits a kind of GIMPLE, which is then subject to GCC optimization pass. That's why we have the native-comp-speed variable, which is mapped directly into the GCC's -On optimization switches, with n = 0..3. Maybe the SBCL compiler has better optimizations, but it is incorrect to say that Emacs's native-compilation has none.