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t=1714978855; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=r/O7CefgTHOepabN6u0Onk2WyfP2dAjTEdlAz13s+3s=; b=G9V6A3xSDLfDPKBM3DxW6411gQsd4np2gJWWJOLYAcgIx/vxdm1F1brRWXirjW0kAUMtVc iJkcf3vzKHe2x0CA== Date: Mon, 6 May 2024 09:00:55 +0200 (CEST) From: Richard Biener To: Martin Uecker cc: Jakub Jelinek , gcc-patches@gcc.gnu.org, Jan Hubicka Subject: Re: [PATCH] middle-end/114931 - type_hash_canon and structual equality types In-Reply-To: Message-ID: <3s4pqo5q-qron-7899-p7q4-rpr81n2q0p90@fhfr.qr> References: <05B84303-9D17-4DAE-A9D9-A77DA3EA7878@suse.de> <39fcac8a1c61acaaa1c80602b76f48ef73f5f885.camel@tugraz.at> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Spam-Score: -4.30 X-Spam-Level: X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-0.979]; MIME_GOOD(-0.10)[text/plain]; MISSING_XM_UA(0.00)[]; MIME_TRACE(0.00)[0:+]; TO_DN_SOME(0.00)[]; ARC_NA(0.00)[]; RCVD_COUNT_ZERO(0.00)[0]; FROM_HAS_DN(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_EQ_ENVFROM(0.00)[]; RCPT_COUNT_THREE(0.00)[4]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:email] X-Spam-Status: No, score=-4.9 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,SPF_HELO_NONE,SPF_PASS,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On Sat, 4 May 2024, Martin Uecker wrote: > Am Freitag, dem 03.05.2024 um 21:16 +0200 schrieb Jakub Jelinek: > > > On Fri, May 03, 2024 at 09:11:20PM +0200, Martin Uecker wrote: > > > > > > > TYPE_CANONICAL as used by the middle-end cannot express this but > > > > > > > > > > Hm. so how does it work now for arrays? > > > > > > Do you have a testcase which doesn't work correctly with the arrays? > > I am mostly trying to understand better how this works. But > if I am not mistaken, the following example would indeed > indicate that we do incorrect aliasing decisions for types > derived from arrays: > > https://godbolt.org/z/rTsE3PhKc This example is about pointer-to-array types, int (*)[2] and int (*)[1] are supposed to be compatible as in receive the same alias set. This is ensured by get_alias_set POINTER_TYPE_P handling, the alias set is supposed to be the same as that of int *. It seems we do restrict the handling a bit, the code does /* Unnest all pointers and references. We also want to make pointer to array/vector equivalent to pointer to its element (see the reasoning above). Skip all those types, too. */ for (p = t; POINTER_TYPE_P (p) || (TREE_CODE (p) == ARRAY_TYPE && (!TYPE_NONALIASED_COMPONENT (p) || !COMPLETE_TYPE_P (p) || TYPE_STRUCTURAL_EQUALITY_P (p))) || TREE_CODE (p) == VECTOR_TYPE; p = TREE_TYPE (p)) where the comment doesn't exactly match the code - but C should never have TYPE_NONALIASED_COMPONENT (p). But maybe I misread the example or it goes wrong elsewhere. Richard. > Martin > > > > > > > E.g. same_type_for_tbaa has > > > type1 = TYPE_MAIN_VARIANT (type1); > > > type2 = TYPE_MAIN_VARIANT (type2); > > > > > > /* Handle the most common case first. */ > > > if (type1 == type2) > > > return 1; > > > > > > /* If we would have to do structural comparison bail out. */ > > > if (TYPE_STRUCTURAL_EQUALITY_P (type1) > > > || TYPE_STRUCTURAL_EQUALITY_P (type2)) > > > return -1; > > > > > > /* Compare the canonical types. */ > > > if (TYPE_CANONICAL (type1) == TYPE_CANONICAL (type2)) > > > return 1; > > > > > > /* ??? Array types are not properly unified in all cases as we have > > > spurious changes in the index types for example. Removing this > > > causes all sorts of problems with the Fortran frontend. */ > > > if (TREE_CODE (type1) == ARRAY_TYPE > > > && TREE_CODE (type2) == ARRAY_TYPE) > > > return -1; > > > ... > > > and later compares alias sets and the like. > > > So, even if int[] and int[0] have different TYPE_CANONICAL, they > > > will be considered maybe the same. Also, guess get_alias_set > > > has some ARRAY_TYPE handling... > > > > > > Anyway, I think we should just go with Richi's patch. > > > > > > Jakub > > > > > > -- Richard Biener SUSE Software Solutions Germany GmbH, Frankenstrasse 146, 90461 Nuernberg, Germany; GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)