From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 29299 invoked by alias); 12 Jul 2014 06:15:51 -0000 Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org Received: (qmail 29287 invoked by uid 89); 12 Jul 2014 06:15:50 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-3.5 required=5.0 tests=AWL,BAYES_00,RP_MATCHES_RCVD autolearn=ham version=3.3.2 X-HELO: mail2-relais-roc.national.inria.fr Received: from mail2-relais-roc.national.inria.fr (HELO mail2-relais-roc.national.inria.fr) (192.134.164.83) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (CAMELLIA256-SHA encrypted) ESMTPS; Sat, 12 Jul 2014 06:15:49 +0000 Received: from ip-205.net-81-220-140.rev.numericable.fr (HELO laptop-mg.local) ([81.220.140.205]) by mail2-relais-roc.national.inria.fr with ESMTP/TLS/DHE-RSA-AES256-SHA; 12 Jul 2014 08:15:38 +0200 Date: Sat, 12 Jul 2014 06:15:00 -0000 From: Marc Glisse To: Richard Biener cc: GCC Patches Subject: Re: update address taken: don't drop clobbers In-Reply-To: Message-ID: References: User-Agent: Alpine 2.11 (DEB 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed X-SW-Source: 2014-07/txt/msg00869.txt.bz2 On Thu, 10 Jul 2014, Richard Biener wrote: >> --- gcc/tree-into-ssa.c (revision 212109) >> +++ gcc/tree-into-ssa.c (working copy) >> @@ -1831,26 +1831,38 @@ maybe_register_def (def_operand_p def_p, >> { >> tree def = DEF_FROM_PTR (def_p); >> tree sym = DECL_P (def) ? def : SSA_NAME_VAR (def); >> >> /* If DEF is a naked symbol that needs renaming, create a new >> name for it. */ >> if (marked_for_renaming (sym)) >> { >> if (DECL_P (def)) >> { >> - tree tracked_var; >> - >> - def = make_ssa_name (def, stmt); >> + if (gimple_clobber_p (stmt) && is_gimple_reg (sym)) > > sym should always be a gimple reg here (it's marked for renaming). > >> + { >> + /* Replace clobber stmts with a default def. Create a new >> + variable so we don't later think we must coalesce, which >> would >> + fail with some ada abnormal PHIs. Still, we try to keep a >> + similar name so error messages make sense. */ >> + unlink_stmt_vdef (stmt); > > I think that's redundant with gsi_replace (note that using gsi_replace > looks dangerous here as it calls update_stmt during SSA rewrite... > that might open a can of worms). IIRC it was failing without unlink_stmt_vdef (maybe that was in a different version of the patch not using gsi_replace, but I don't think so). I was hoping that a clobber had little enough effects that update_stmt was unlikely to break anything. Anyway it doesn't matter if I use your suggestion below. >> + gsi_replace (&gsi, gimple_build_nop (), true); >> + tree id = DECL_NAME (sym); >> + const char* name = id ? IDENTIFIER_POINTER (id) : 0; >> + tree newvar = create_tmp_var (TREE_TYPE (sym), name); >> + def = get_or_create_ssa_default_def (cfun, newvar); > > So - can't you simply do > > gimple_assign_set_rhs_from_tree (&gsi, > get_or_create_dda_default_def (cfun, sym)); > > ? Thus replace x = CLOBBER; with x_3 = x_2(D); > >> + } >> + else > > and of course still rewrite the DEF then. IMHO the copy-propagation > you do is premature optimization. I'll try that. I was trying to remain as close as possible to what you wrote in rewrite_stmt: if (gimple_clobber_p (stmt) && is_gimple_reg (var)) { /* If we rewrite a DECL into SSA form then drop its clobber stmts and replace uses with a new default def. */ gcc_checking_assert (TREE_CODE (var) == VAR_DECL && !gimple_vdef (stmt)); gsi_replace (si, gimple_build_nop (), true); register_new_def (get_or_create_ssa_default_def (cfun, var), var); break; } I'll be away next week, but I'll re-read all the replies carefully when I come back. -- Marc Glisse