From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 73243 invoked by alias); 9 Jul 2019 12:31:28 -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 73151 invoked by uid 89); 9 Jul 2019 12:31:28 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-5.0 required=5.0 tests=AWL,BAYES_00 autolearn=ham version=3.3.1 spammy= X-HELO: nikam.ms.mff.cuni.cz Received: from nikam.ms.mff.cuni.cz (HELO nikam.ms.mff.cuni.cz) (195.113.20.16) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Tue, 09 Jul 2019 12:31:27 +0000 Received: by nikam.ms.mff.cuni.cz (Postfix, from userid 16202) id CE7C328252A; Tue, 9 Jul 2019 14:31:24 +0200 (CEST) Date: Tue, 09 Jul 2019 12:41:00 -0000 From: Jan Hubicka To: Richard Biener Cc: gcc-patches@gcc.gnu.org, d@dcepelik.cz Subject: Re: Make nonoverlapping_component_refs work with duplicated main variants Message-ID: <20190709123124.rdelfgb5gkdebdr4@kam.mff.cuni.cz> References: <20190708072649.vqd5u6jxsz5ybtt7@kam.mff.cuni.cz> <20190709114917.qva4nb2h7j5vzdur@kam.mff.cuni.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170113 (1.7.2) X-SW-Source: 2019-07/txt/msg00689.txt.bz2 > For consistency yes I guess but IIRC they cannot really appear in > FIELD_DECLs. OK, i tought that if I put SVE into structures, we may end up with these. > > + /* Different fields of the same record type cannot overlap. > > + ??? Bitfields can overlap at RTL level so punt on them. */ > > + if (DECL_BIT_FIELD (field1) && DECL_BIT_FIELD (field2)) > > + return 0; > > + > > don't you need the DECL_BIT_FIELD_REPRESENTATIVE check here as well? > I'd do > > if (DECL_BIT_FIELD_REPRESENTATIVE (field1)) > field1 = DECL_BIT_FIELD_REPRESENTATIVE (field1); > if (DECL_BIT_FIELD_REPRESENTATIVE (field2)) > field2 = DECL_BIT_FIELD_REPRESENTATIVE (field2); > > thus use the representative for the overlap check. It might > be the case that we can improve here and if we do this > can do the DECL_BIT_FIELD check after this (hoping the > representative doesn't have it set). OK. > > > + if (tree_int_cst_equal (DECL_FIELD_OFFSET (field1), > > + DECL_FIELD_OFFSET (field2)) > > + && tree_int_cst_equal (DECL_FIELD_BIT_OFFSET (field1), > > + DECL_FIELD_BIT_OFFSET (field2))) > > + return 0; > > In gimple_compare_field_offset this was fast-pathed for > DECL_OFFSET_ALIGN (f1) == DECL_OFFSET_ALIGN (f2) so I suggest to > do that here as well. Note that DECL_FIELD_OFFSET can be > a non-constant which means you cannot use tree_int_cst_equal > unconditionally here but you have to use operand_equal_p. tree_int_cst_equal will return false if offsets are not INTEGER_CST. I was not sure if I can safely use operand_equal_p. What happens for fields with variable offsets when I inline two copies of same function which takes size as parameter and make the size different? Will I get here proper SSA name so operand_equal_p will work? If so, I still see no point for fast-path for DECL_OFFSET_ALIGN. In many cases BIT_OFFSET will be just 0, so even if offset alignments are different we are likely going to hit this fast path avoiding parsing trees later. > > > + /* Note that it may be possible to use component_ref_field_offset > > + which would provide offsets as trees. However constructing and folding > > + trees is expensive and does not seem to be worth the compile time > > + cost. */ > > + > > + poly_uint64 offset1, offset2; > > + poly_uint64 bit_offset1, bit_offset2; > > + poly_uint64 size1, size2; > > I think you need poly_offset_int here since you convert to bits below. > > The gimple_compare_field_offset checking way looks cheaper btw, so > I wonder why you don't simply call it but replicate things here? > When do we expect to have partially overlapping field decls? Even > when considering canonical type merging? Because the types I am comparing may not have same canonical types. nonoverlapping_component_refs_since_match_p is called when we prove that base pointers are the same (even with -fno-strict-aliasing). In such cases the access paths may be based on completely different types. The point of nonoverlapping_component_refs_since_match_p is to match them as far as possible when they are semantically equivalent in hope to get non-overlapping refs in the last step. This is stronger than the get_base_ref_and_extend based check in presence of non-constant ARRAY_REFs. Honza