From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 73014 invoked by alias); 6 Apr 2017 07:47:14 -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 72997 invoked by uid 89); 6 Apr 2017 07:47:13 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-11.1 required=5.0 tests=BAYES_00,GIT_PATCH_2,GIT_PATCH_3,KAM_ASCII_DIVIDERS,RP_MATCHES_RCVD,SPF_PASS autolearn=ham version=3.3.2 spammy=arise X-HELO: mx2.suse.de Received: from mx2.suse.de (HELO mx2.suse.de) (195.135.220.15) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Thu, 06 Apr 2017 07:47:12 +0000 Received: from relay1.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 2DD03AC4A; Thu, 6 Apr 2017 07:47:11 +0000 (UTC) Date: Thu, 06 Apr 2017 07:47:00 -0000 From: Richard Biener To: Bernd Edlinger cc: Jakub Jelinek , Jonathan Wakely , Florian Weimer , GCC Patches , Jason Merrill , Jeff Law Subject: Re: [PATCH] Add a new type attribute always_alias (PR79671) In-Reply-To: Message-ID: References: <6a5109d6-81fb-c36c-e525-b2ed984760dc@redhat.com> <21E940B5-C8C4-4A86-8C15-49A86547DD87@suse.de> <20170405160333.GR4425@redhat.com> <20170405160849.GV17461@tucnak> User-Agent: Alpine 2.20 (LSU 67 2015-01-07) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-SW-Source: 2017-04/txt/msg00264.txt.bz2 On Wed, 5 Apr 2017, Bernd Edlinger wrote: > On 04/05/17 19:22, Bernd Edlinger wrote: > > On 04/05/17 18:08, Jakub Jelinek wrote: > > > > Yes, exactly. I really want to reach the deadline for gcc-7. > > Fixing the name is certainly the most important first step, > > and if everybody agrees on "typeless_storage", for the name > > I can start with adjusting the name, and look into how > > to use a spare type-flag that should be a mechanical change. > > > > Jakub, I just renamed the attribute and reworked the patch > as you suggested, reg-testing is not yet completed, but > it looks good so far. I also added a few more tests. > > I have changed the documentation as Richi suggested, but > I am not too sure what to say here. The alias.c changes are not sufficient. I think what you want is sth like Index: gcc/alias.c =================================================================== --- gcc/alias.c (revision 246678) +++ gcc/alias.c (working copy) @@ -136,6 +136,9 @@ struct GTY(()) alias_set_entry { bool is_pointer; /* Nonzero if is_pointer or if one of childs have has_pointer set. */ bool has_pointer; + /* Nonzero if we have a child serving as typeless storage (or are + such storage ourselves). */ + bool has_typeless_storage; /* The children of the alias set. These are not just the immediate children, but, in fact, all descendants. So, if we have: @@ -419,7 +422,8 @@ alias_set_subset_of (alias_set_type set1 /* Check if set1 is a subset of set2. */ ase2 = get_alias_set_entry (set2); if (ase2 != 0 - && (ase2->has_zero_child + && (ase2->has_typeless_storage + || ase2->has_zero_child || (ase2->children && ase2->children->get (set1)))) return true; @@ -825,6 +829,7 @@ init_alias_set_entry (alias_set_type set ase->has_zero_child = false; ase->is_pointer = false; ase->has_pointer = false; + ase->has_typeless_storage = false; gcc_checking_assert (!get_alias_set_entry (set)); (*alias_sets)[set] = ase; return ase; @@ -955,6 +960,7 @@ get_alias_set (tree t) Just be pragmatic here and make sure the array and its element type get the same alias set assigned. */ else if (TREE_CODE (t) == ARRAY_TYPE + && ! TYPE_TYPELESS_STORAGE (t) && (!TYPE_NONALIASED_COMPONENT (t) || TYPE_STRUCTURAL_EQUALITY_P (t))) set = get_alias_set (TREE_TYPE (t)); @@ -1094,6 +1100,15 @@ get_alias_set (tree t) TYPE_ALIAS_SET (t) = set; + if (TREE_CODE (t) == ARRAY_TYPE + && TYPE_TYPELESS_STORAGE (t)) + { + alias_set_entry *ase = get_alias_set_entry (set); + if (!ase) + ase = init_alias_set_entry (set); + ase->has_typeless_storage = true; + } + /* If this is an aggregate type or a complex type, we must record any component aliasing information. */ if (AGGREGATE_TYPE_P (t) || TREE_CODE (t) == COMPLEX_TYPE) @@ -1173,6 +1188,8 @@ record_alias_subset (alias_set_type supe superset_entry->has_zero_child = true; if (subset_entry->has_pointer) superset_entry->has_pointer = true; + if (subset_entry->has_typeless_storage) + superset_entry->has_typeless_storage = true; if (subset_entry->children) { please also restrict TYPE_TYPELESS_STORAGE to ARRAY_TYPEs (otherwise more complications will arise). Index: gcc/cp/class.c =================================================================== --- gcc/cp/class.c (revision 246678) +++ gcc/cp/class.c (working copy) @@ -2083,7 +2083,8 @@ fixup_attribute_variants (tree t) tree attrs = TYPE_ATTRIBUTES (t); unsigned align = TYPE_ALIGN (t); bool user_align = TYPE_USER_ALIGN (t); - bool may_alias = lookup_attribute ("may_alias", attrs); + bool may_alias = TYPE_TYPELESS_STORAGE (t) + || lookup_attribute ("may_alias", attrs); if (may_alias) fixup_may_alias (t); @@ -7345,6 +7348,12 @@ finish_struct_1 (tree t) the class or perform any other required target modifications. */ targetm.cxx.adjust_class_at_definition (t); + if (cxx_dialect >= cxx1z && cxx_type_contains_byte_buffer (t)) + { + TYPE_TYPELESS_STORAGE (t) = 1; + fixup_attribute_variants (t); ... I don't think you need all this given alias.c only looks at TYPE_MAIN_VARIANTs. Index: gcc/cp/decl.c =================================================================== --- gcc/cp/decl.c (revision 246678) +++ gcc/cp/decl.c (working copy) @@ -14081,10 +14081,11 @@ start_enum (tree name, tree enumtype, tree underly enumtype = pushtag (name, enumtype, /*tag_scope=*/ts_current); /* std::byte aliases anything. */ - if (enumtype != error_mark_node + if (cxx_dialect >= cxx1z + && enumtype != error_mark_node && TYPE_CONTEXT (enumtype) == std_node && !strcmp ("byte", TYPE_NAME_STRING (enumtype))) - TYPE_ALIAS_SET (enumtype) = 0; + TYPE_TYPELESS_STORAGE (enumtype) = 1; } else not needed (but also not sufficient - you need to handle arrays of byte somewhere). @@ -1491,6 +1491,7 @@ struct GTY(()) tree_type_common { unsigned needs_constructing_flag : 1; unsigned transparent_aggr_flag : 1; unsigned restrict_flag : 1; + unsigned typeless_storage_flag : 1; unsigned contains_placeholder_bits : 2; ENUM_BITFIELD(machine_mode) mode : 8; bits are grouped in groups of 8 bits, this breaks it. @@ -8041,7 +8041,8 @@ build_pointer_type_for_mode (tree to_type, machine /* If the pointed-to type has the may_alias attribute set, force a TYPE_REF_CAN_ALIAS_ALL pointer to be generated. */ - if (lookup_attribute ("may_alias", TYPE_ATTRIBUTES (to_type))) + if (TYPE_TYPELESS_STORAGE (to_type) + || lookup_attribute ("may_alias", TYPE_ATTRIBUTES (to_type))) can_alias_all = true; /* In some cases, languages will have things that aren't a POINTER_TYPE @@ -8110,7 +8111,8 @@ build_reference_type_for_mode (tree to_type, machi /* If the pointed-to type has the may_alias attribute set, force a TYPE_REF_CAN_ALIAS_ALL pointer to be generated. */ - if (lookup_attribute ("may_alias", TYPE_ATTRIBUTES (to_type))) + if (TYPE_TYPELESS_STORAGE (to_type) + || lookup_attribute ("may_alias", TYPE_ATTRIBUTES (to_type))) can_alias_all = true; /* In some cases, languages will have things that aren't a not needed. +/* Nonzero if the type should behave like a character type + with respect to aliasing sementics. */ +#define TYPE_TYPELESS_STORAGE(NODE) \ + (TYPE_CHECK (NODE)->type_common.typeless_storage_flag) ARRAY_TYPE_CHECK (NODE)-> Richard.