From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 3FF173858C41; Thu, 20 Jun 2024 01:58:09 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 3FF173858C41 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1718848689; bh=lkZ9kvNaKavU0hICc9MChXvUoT2g80s8rDcmWDkek2w=; h=From:To:Subject:Date:In-Reply-To:References:From; b=VLC0uEMwRH6GWKsCxnI0h7dHEMA4/0wLaFcTkaqj6dbFpIuv/Y8PkeFaVq8OORDVx pRANu6F4p0vG+5wTT3J2Vy27MwYoPRZkf24fkGFyjdLfhnfZrRJVaWoZHdHHzxpedj FrRntGWgCayFPnJqG0vPMv76cm2Z6HEIiyUD21hw= From: "xry111 at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug middle-end/115551] [missed optimization] "c1 << (a + c2)" not optimized into "(c1 << c2) << a" Date: Thu, 20 Jun 2024 01:58:08 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: middle-end X-Bugzilla-Version: 15.0 X-Bugzilla-Keywords: missed-optimization X-Bugzilla-Severity: normal X-Bugzilla-Who: xry111 at gcc dot gnu.org X-Bugzilla-Status: UNCONFIRMED 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=3D115551 Xi Ruoyao changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |xry111 at gcc dot gnu.org --- Comment #1 from Xi Ruoyao --- "c1 << (-5 + 5)" is fine but "(c1 << -5) << 5" invokes undefined behavior.= =20 Thus we need some range info to do this optimization.=