From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 26597 invoked by alias); 8 Aug 2009 10:36:36 -0000 Received: (qmail 26501 invoked by uid 48); 8 Aug 2009 10:36:19 -0000 Date: Sat, 08 Aug 2009 10:36:00 -0000 Message-ID: <20090808103619.26500.qmail@sourceware.org> X-Bugzilla-Reason: CC References: Subject: [Bug middle-end/41004] missed merge of basic blocks In-Reply-To: Reply-To: gcc-bugzilla@gcc.gnu.org To: gcc-bugs@gcc.gnu.org From: "rguenth at gcc dot gnu dot org" Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org X-SW-Source: 2009-08/txt/msg00792.txt.bz2 ------- Comment #3 from rguenth at gcc dot gnu dot org 2009-08-08 10:36 ------- I would suggest to closely look at SSA expansion as well. There is I think still the regression from pre-SSA expand that it doesn't expand PHI nodes optimally at -Os (pre-SSA expand split common PHI args into extra blocks to minimize copy instructions which is something that can be done as a tree level transform). Like BB5: # a_1 = PHI to BB6: # tmp_4 = PHI BB5: # a_1 = PHI which we usually don't want and in fact undo during mergephi. But it needs one less copy if a_2 and tmp_4 can be coalesced together. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41004