From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) by sourceware.org (Postfix) with ESMTP id 0E5EA3858C3A for ; Tue, 21 Sep 2021 12:25:46 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 0E5EA3858C3A Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=kernel.crashing.org Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 18LCOjtK016660; Tue, 21 Sep 2021 07:24:45 -0500 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 18LCOiRO016652; Tue, 21 Sep 2021 07:24:44 -0500 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Tue, 21 Sep 2021 07:24:44 -0500 From: Segher Boessenkool To: Jeff Law Cc: Roger Sayle , "'GCC Patches'" Subject: Re: [PATCH] Simplify paradoxical subreg extensions of TRUNCATE Message-ID: <20210921122444.GC1583@gate.crashing.org> References: <001401d7a2a5$5bf07db0$13d17910$@nextmovesoftware.com> <20210906101414.GT1583@gate.crashing.org> <001401d7a312$d7ca09c0$875e1d40$@nextmovesoftware.com> <20210906142454.GU1583@gate.crashing.org> <7c18f738-6399-451d-d1d1-25f010d2e555@gmail.com> <20210921002321.GA1583@gate.crashing.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.3i X-Spam-Status: No, score=-3.4 required=5.0 tests=BAYES_00, JMQ_SPF_NEUTRAL, KAM_DMARC_STATUS, SPF_HELO_PASS, SPF_PASS, TXREP autolearn=no autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 21 Sep 2021 12:25:48 -0000 On Mon, Sep 20, 2021 at 10:18:15PM -0600, Jeff Law wrote: > On 9/20/2021 6:23 PM, Segher Boessenkool wrote: > >There is no such thing as "earlier than simplify-rtx", that is the > >point. simplify-rtx is not a pass: it is like a library that is used > >from all over the RTL routines. > I'm referring to earlier in the call chain, not an earlier pass. Sorry I > wasn't clear about that. Ah okay, I see. > If we were catching the scenario which led to the creation of (subreg > (truncate)) in combine and instead of creating (subreg (truncate)) we > instead created the simplified, correct form would that ease your concerns? Yes please. And combine has access to the original instructions, so can make sure to only ever create something with the same semantics. Thanks, Segher