From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 2921 invoked by alias); 27 Jan 2005 01:43:38 -0000 Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org Received: (qmail 2875 invoked by uid 48); 27 Jan 2005 01:43:34 -0000 Date: Thu, 27 Jan 2005 01:43:00 -0000 Message-ID: <20050127014334.2874.qmail@sourceware.org> From: "steven at gcc dot gnu dot org" To: gcc-bugs@gcc.gnu.org In-Reply-To: <20040909235415.17387.hjl@lucon.org> References: <20040909235415.17387.hjl@lucon.org> Reply-To: gcc-bugzilla@gcc.gnu.org Subject: [Bug rtl-optimization/17387] Redundant instructions in loop optimization X-Bugzilla-Reason: CC X-SW-Source: 2005-01/txt/msg03967.txt.bz2 List-Id: ------- Additional Comments From steven at gcc dot gnu dot org 2005-01-27 01:43 ------- GCC can't see that this is a NOP because of the zero_extend: #(insn 34 30 37 (set (reg:DI 0 ax [orig:76 D.1460 ] [76]) # (zero_extend:DI (reg:SI 0 ax [orig:70 D.1460 ] [70]))) 111 {zero_extendsidi2_rex64} (insn_list:REG_DEP_ANTI 30 (insn_list:REG_DEP_TRUE 29 (nil))) # (nil)) mov %eax, %eax # D.1460, D.1460 # 34 zero_extendsidi2_rex64/1 [length = 3] Perhaps we should have a peephole2 for this. I'm curious why we can not eliminate the move earlier on, though. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17387