From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 22362 invoked by alias); 29 Jan 2002 04:06:10 -0000 Mailing-List: contact gcc-prs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Archive: List-Post: List-Help: Sender: gcc-prs-owner@gcc.gnu.org Received: (qmail 22348 invoked by uid 71); 29 Jan 2002 04:06:10 -0000 Date: Mon, 28 Jan 2002 20:06:00 -0000 Message-ID: <20020129040610.22341.qmail@sources.redhat.com> To: nobody@gcc.gnu.org Cc: gcc-prs@gcc.gnu.org, From: Craig Rodrigues Subject: Re: optimization/5244: Dead code in simplify_logical() Reply-To: Craig Rodrigues X-SW-Source: 2002-01/txt/msg01015.txt.bz2 List-Id: The following reply was made to PR optimization/5244; it has been noted by GNATS. From: Craig Rodrigues To: gcc-gnats@gcc.gnu.org, gcc-prs@gcc.gnu.org, Kai.Tietz@onevision.de, gcc-bugs@gcc.gnu.org, nobody@gcc.gnu.org Cc: Subject: Re: optimization/5244: Dead code in simplify_logical() Date: Mon, 28 Jan 2002 23:06:21 -0500 In PR 5244: http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=5244 you submitted a patch, which I have reproduced here in unified context diff format. Can you explain why this patch is necessary? I did not understand your explanation. Index: combine.c =================================================================== RCS file: /cvs/gcc/gcc/gcc/combine.c,v retrieving revision 1.183.2.8 diff -u -r1.183.2.8 combine.c --- combine.c 2001/11/05 19:10:32 1.183.2.8 +++ combine.c 2002/01/29 03:58:03 @@ -5391,8 +5391,25 @@ If we have (and (ior A B) C), apply the distributive law and then the inverse distributive law to see if things simplify. */ + /* Similarly, taking advantage of the fact that + (and (not A) (xor B C)) == (xor (ior A B) (ior A C)) */ + + if (GET_CODE (op0) == NOT && GET_CODE (op1) == XOR) + return apply_distributive_law + (gen_binary (XOR, mode, + gen_binary (IOR, mode, XEXP (op0, 0), XEXP (op1, 0)), + gen_binary (IOR, mode, copy_rtx (XEXP (op0, 0)), + XEXP (op1, 1)))); + + else if (GET_CODE (op1) == NOT && GET_CODE (op0) == XOR) + return apply_distributive_law + (gen_binary (XOR, mode, + gen_binary (IOR, mode, XEXP (op1, 0), XEXP (op0, 0)), + gen_binary (IOR, mode, copy_rtx (XEXP (op1, 0)), XEXP (op0, 1)))); + if (GET_CODE (op0) == IOR || GET_CODE (op0) == XOR) { + /* ??? May we get better code, if we do this optimization anyway */ x = apply_distributive_law (gen_binary (GET_CODE (op0), mode, gen_binary (AND, mode, XEXP (op0, 0), op1), @@ -5409,21 +5426,6 @@ gen_binary (AND, mode, XEXP (op1, 1), copy_rtx (op0)))); - /* Similarly, taking advantage of the fact that - (and (not A) (xor B C)) == (xor (ior A B) (ior A C)) */ - - if (GET_CODE (op0) == NOT && GET_CODE (op1) == XOR) - return apply_distributive_law - (gen_binary (XOR, mode, - gen_binary (IOR, mode, XEXP (op0, 0), XEXP (op1, 0)), - gen_binary (IOR, mode, copy_rtx (XEXP (op0, 0)), - XEXP (op1, 1)))); - - else if (GET_CODE (op1) == NOT && GET_CODE (op0) == XOR) - return apply_distributive_law - (gen_binary (XOR, mode, - gen_binary (IOR, mode, XEXP (op1, 0), XEXP (op0, 0)), - gen_binary (IOR, mode, copy_rtx (XEXP (op1, 0)), XEXP (op0, 1)))); break; case IOR: -- Craig Rodrigues http://www.gis.net/~craigr rodrigc@mediaone.net