From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 22657 invoked by alias); 17 Jul 2006 13:34:56 -0000 Received: (qmail 22617 invoked by alias); 17 Jul 2006 13:34:48 -0000 Date: Mon, 17 Jul 2006 13:34:00 -0000 Message-ID: <20060717133448.22616.qmail@sourceware.org> X-Bugzilla-Reason: CC References: Subject: [Bug tree-optimization/20643] [4.0/4.1/4.2 Regression] Tree loop optimizer does worse job than RTL loop optimizer In-Reply-To: Reply-To: gcc-bugzilla@gcc.gnu.org To: gcc-bugs@gcc.gnu.org From: "dberlin at dberlin dot org" 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/msg01327.txt.bz2 List-Id: ------- Comment #14 from dberlin at gcc dot gnu dot org 2006-07-17 13:34 ------- Subject: Re: [4.0/4.1/4.2 Regression] Tree loop optimizer does worse job than RTL loop optimizer rakdver at gcc dot gnu dot org wrote: > ------- Comment #13 from rakdver at gcc dot gnu dot org 2006-07-17 11:54 ------- > (In reply to comment #12) >> The test case in comment #11 looks like a classic store motion opportunity to >> me. GCC 3.3 performs the store motion, GCC 4.2 r115467 does not. >> >> Zdenek, I thought tree-ssa-lim should be able to do store motion in loops? > > Yes, however again, the alias analysis does not tell it that a[0] does not > alias a[1]; once that is fixed, tree-ssa-lim should work just fine. This is because it's an incoming parameter, and as a result, this doesn't look at all like an array access, but just a random pointer access. I have no plans to make the alias analysis algorithm reconstruct array indexes from random pointer arithmetic. --Dan -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20643