[{"id":3685119,"web_url":"http://patchwork.ozlabs.org/comment/3685119/","msgid":"<0E1894FB-B964-4616-8377-219D5A3FE1FB@suse.de>","list_archive_url":null,"date":"2026-05-01T12:43:59","subject":"Re: [PATCH] strlen: Adjust objsz arg in __strcat_chk -> __stpcpy_chk\n transformation [PR125079]","submitter":{"id":4338,"url":"http://patchwork.ozlabs.org/api/people/4338/","name":"Richard Biener","email":"rguenther@suse.de"},"content":"> Am 01.05.2026 um 08:49 schrieb Jakub Jelinek :\n> \n> Hi!\n> \n> As the following testcase shows, we have two different transformations\n> of __strcat_chk. One done in strlen_pass::handle_builtin_strcat,\n> which transforms __strcat_chk (x, y, z) if we know beforehand strlen (x),\n> so something like:\n> l = strlen (x);\n> __strcat_chk (x, y, z);\n> and since PR87672 we change that to\n> l = strlen (x);\n> __strcpy_chk (x + l, y, z - l);\n> i.e. decrease the objsz in\n> if (objsz)\n> {\n> objsz = fold_build2_loc (loc, MINUS_EXPR, TREE_TYPE (objsz), objsz,\n> fold_convert_loc (loc, TREE_TYPE (objsz),\n> unshare_expr (dstlen)));\n> objsz = force_gimple_operand_gsi (&m_gsi, objsz, true, NULL_TREE, true,\n> GSI_SAME_STMT);\n> }\n> And another transformation is when we have earlier __strcat_chk (x, y, z)\n> call and want to compute strlen (x) after that. In that case\n> get_string_length transforms\n> __strcat_chk (x, y, z);\n> to\n> t = strlen (x);\n> l = __stpcpy_chk (x + t, y, z) - x;\n> where l is the len we are looking for. This patch changes it similarly to\n> the PR87672 to\n> t = strlen (x);\n> l = __stpcpy_chk (x + t, y, z - t) - x;\n> instead.\n> \n> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk/16.2?\n\nOk\n\nRichard \n\n> 2026-05-01 Jakub Jelinek \n> \n> PR tree-optimization/125079\n> * tree-ssa-strlen.cc (get_string_length): Transform\n> __strcat_chk (x, y, z) when we need strlen (x) afterwards into\n> l1 = strlen (x); l = __stpcpy_chk (x + l1, y, z - l1) - x;\n> where l is the strlen (x), instead of using z as last __stpcpy_chk\n> argument.\n> \n> * gcc.dg/strlenopt-97.c: New test.\n> \n> --- gcc/tree-ssa-strlen.cc.jj 2026-04-27 09:53:40.000000000 +0200\n> +++ gcc/tree-ssa-strlen.cc 2026-04-30 15:30:48.827666196 +0200\n> @@ -848,7 +848,7 @@ get_string_length (strinfo *si)\n> attempt to compute the length from the call statement. */\n> if (si->stmt)\n> {\n> - gimple *stmt = si->stmt, *lenstmt;\n> + gimple *stmt = si->stmt, *lenstmt = NULL;\n> tree callee, lhs, fn, tem;\n> location_t loc;\n> gimple_stmt_iterator gsi;\n> @@ -902,6 +902,17 @@ get_string_length (strinfo *si)\n> gimple_call_set_fndecl (stmt, fn);\n> lhs = make_ssa_name (TREE_TYPE (TREE_TYPE (fn)), stmt);\n> gimple_call_set_lhs (stmt, lhs);\n> + if (DECL_FUNCTION_CODE (callee) == BUILT_IN_STRCAT_CHK)\n> + {\n> + tree objsz = gimple_call_lhs (lenstmt);\n> + gimple *g\n> + = gimple_build_assign (make_ssa_name (TREE_TYPE (objsz)),\n> + MINUS_EXPR, gimple_call_arg (stmt, 2),\n> + objsz);\n> + gimple_set_location (g, gimple_location (stmt));\n> + gsi_insert_before (&gsi, g, GSI_SAME_STMT);\n> + gimple_call_set_arg (stmt, 2, gimple_assign_lhs (g));\n> + }\n> update_stmt (stmt);\n> if (dump_file && (dump_flags & TDF_DETAILS) != 0)\n> {\n> --- gcc/testsuite/gcc.dg/strlenopt-97.c.jj 2026-04-30 16:34:55.930209569 +0200\n> +++ gcc/testsuite/gcc.dg/strlenopt-97.c 2026-04-30 16:34:52.050276667 +0200\n> @@ -0,0 +1,33 @@\n> +/* PR tree-optimization/125079 */\n> +/* { dg-do compile } */\n> +/* { dg-options \"-O2 -fdump-tree-strlen1\" } */\n> +/* { dg-final { scan-tree-dump-times \"__builtin___strcpy_chk \\\\\\(\" 1 \"strlen1\" } } */\n> +/* { dg-final { scan-tree-dump-not \"__builtin___strcpy_chk \\\\\\(\\[^\\n\\r]*, 64\\\\\\)\" \"strlen1\" } } */\n> +/* { dg-final { scan-tree-dump-times \"__builtin___stpcpy_chk \\\\\\(\" 1 \"strlen1\" } } */\n> +/* { dg-final { scan-tree-dump-not \"__builtin___stpcpy_chk \\\\\\(\\[^\\n\\r]*, 128\\\\\\)\" \"strlen1\" } } */\n> +\n> +typedef __SIZE_TYPE__ size_t;\n> +void foo (char *, int);\n> +char *stpcpy (char *, const char *);\n> +\n> +size_t\n> +bar (char *r)\n> +{\n> + char buf[64];\n> + foo (buf, 0);\n> + size_t ret = __builtin_strlen (buf);\n> + __builtin___strcat_chk (buf, r, 64);\n> + foo (buf, 1);\n> + return ret;\n> +}\n> +\n> +size_t\n> +baz (char *r)\n> +{\n> + char buf[128];\n> + foo (buf, 2);\n> + __builtin___strcat_chk (buf, r, 128);\n> + size_t ret = __builtin_strlen (buf);\n> + foo (buf, 3);\n> + return ret;\n> +}\n> \n> Jakub\n>","headers":{"Return-Path":"","X-Original-To":["incoming@patchwork.ozlabs.org","gcc-patches@gcc.gnu.org"],"Delivered-To":["patchwork-incoming@legolas.ozlabs.org","gcc-patches@gcc.gnu.org"],"Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=suse.de header.i=@suse.de header.a=rsa-sha256\n header.s=susede2_rsa header.b=RXeOagJH;\n\tdkim=pass header.d=suse.de header.i=@suse.de header.a=ed25519-sha256\n header.s=susede2_ed25519 header.b=/gcLq1a6;\n\tdkim=pass (1024-bit key) header.d=suse.de header.i=@suse.de\n header.a=rsa-sha256 header.s=susede2_rsa header.b=T1SiyqLE;\n\tdkim=neutral header.d=suse.de header.i=@suse.de header.a=ed25519-sha256\n header.s=susede2_ed25519 header.b=Oc/u82Hv;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=temperror (SPF Temporary Error: DNS Timeout) smtp.mailfrom=gcc.gnu.org\n (client-ip=2620:52:6:3111::32; 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charset=utf-8","Content-Transfer-Encoding":"quoted-printable","From":"Richard Biener ","Mime-Version":"1.0 (1.0)","Subject":"Re: [PATCH] strlen: Adjust objsz arg in __strcat_chk -> __stpcpy_chk\n transformation [PR125079]","Date":"Fri, 1 May 2026 14:43:59 +0200","Message-Id":"<0E1894FB-B964-4616-8377-219D5A3FE1FB@suse.de>","References":"","Cc":"gcc-patches@gcc.gnu.org","In-Reply-To":"","To":"Jakub Jelinek ","X-Mailer":"iPhone Mail (23E261)","X-Spamd-Result":"default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%];\n NEURAL_HAM_LONG(-1.00)[-1.000];\n NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain];\n ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[];\n APPLE_IOS_MAILER_COMMON(0.00)[]; MIME_TRACE(0.00)[0:+];\n FUZZY_RATELIMITED(0.00)[rspamd.com];\n MID_RHS_MATCH_FROM(0.00)[]; RCVD_TLS_ALL(0.00)[];\n RCPT_COUNT_TWO(0.00)[2]; FROM_EQ_ENVFROM(0.00)[];\n FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[];\n RCVD_COUNT_TWO(0.00)[2];\n DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519];\n TO_MATCH_ENVRCPT_ALL(0.00)[];\n DBL_BLOCKED_OPENRESOLVER(0.00)[tree-ssa-strlen.cc:url, suse.de:mid,\n imap1.dmz-prg2.suse.org:helo]","X-BeenThere":"gcc-patches@gcc.gnu.org","X-Mailman-Version":"2.1.30","Precedence":"list","List-Id":"Gcc-patches mailing list ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"gcc-patches-bounces~incoming=patchwork.ozlabs.org@gcc.gnu.org"}}]