From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 4D5E23858404; Fri, 9 Feb 2024 21:58:03 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 4D5E23858404 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1707515883; bh=7YDMDfI8rY9KHfMFT/Wd7mViP9He3Nk2iTV7QLuqYUM=; h=From:To:Subject:Date:In-Reply-To:References:From; b=Wmff8XhNL5ad1GRKR0cXl8giqwHSIP9R9ejYBFFW4HBK3ofLYRMyQLH3ZdZdl3rId LN4YZekm8cm1qFHRGZJerKHlrvaOAZiGt5uh4iIphg5wzEMmuBfcKYiMxL3qgFGuSS H+5I83D8OvdH9a+DCFXxmrjLEPXCzQN2hfS99tEI= From: "jakub at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug target/113764] [X86] Generates lzcnt when bsr is sufficient Date: Fri, 09 Feb 2024 21:58:02 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: target X-Bugzilla-Version: 13.2.1 X-Bugzilla-Keywords: missed-optimization X-Bugzilla-Severity: normal X-Bugzilla-Who: jakub at gcc dot gnu.org X-Bugzilla-Status: NEW X-Bugzilla-Resolution: X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: cc Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 List-Id: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113764 Jakub Jelinek changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |jakub at gcc dot gnu.org --- Comment #3 from Jakub Jelinek --- It is far more complicated than this. When TARGET_LZCNT is on, CLZ_DEFINED_VALUE_AT_ZERO is 2 and already in GIMP= LE opts can use the fact that it has particular behavior on zero argument. Before my _BitInt changes for clz/ctz etc., there was no way to differentia= te it in GIMPLE except for builtin (which had UB at zero) vs. ifn (which had it depending on C?Z_DEFINED_VALUE_AT_ZERO). Now even ifn can be UB at zero (single argument) or well defined (two). But still on RTL we have just one thing, CLZ or CTZ rtxes which honor C?Z_DEFINED_VALUE_AT_ZERO for the particular mode. So, I think having at least in one function some lzcnt and some bsr insns wouldn't be possible.=