From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 27618 invoked by alias); 4 Jul 2006 13:15:19 -0000 Received: (qmail 27576 invoked by uid 48); 4 Jul 2006 13:15:11 -0000 Date: Tue, 04 Jul 2006 13:15:00 -0000 Message-ID: <20060704131511.27564.qmail@sourceware.org> X-Bugzilla-Reason: CC References: Subject: [Bug target/27827] [4.0/4.1/4.2 Regression] gcc 4 produces worse x87 code on all platforms than gcc 3 In-Reply-To: Reply-To: gcc-bugzilla@gcc.gnu.org To: gcc-bugs@gcc.gnu.org From: "whaley at cs dot utsa dot edu" 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 X-SW-Source: 2006-07/txt/msg00165.txt.bz2 List-Id: ------- Comment #29 from whaley at cs dot utsa dot edu 2006-07-04 13:15 ------- Guys, The integer and fp differences do not appear to be strongly related. In particular, on my P4e, gcc 4's integer code is actually faster than gcc 3's. Further, if you look at the assemblies of the integer code, it does not have the extra dependencies that gcc 4's x87 code has. In integer, both gcc 3 and 4 explicitly do all loads to registers. I haven't scoped it in detail, but the main difference appears to be in scheduling, with gcc 3 performing a bunch of loads, then a bunch of computations, and gcc 4 intermixing them more. So, we'd need a new series of runs to see which integer schedule is better, but the integer code should not be studied to solve the x87 problem. Thanks, Clint -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27827