[{"id":3673236,"web_url":"http://patchwork.ozlabs.org/comment/3673236/","msgid":"","list_archive_url":null,"date":"2026-04-03T17:18:00","subject":"Re: [PATCH] Correct x86: Call ix86_access_stack_p only for larger\n alignment","submitter":{"id":4387,"url":"http://patchwork.ozlabs.org/api/people/4387/","name":"H.J. Lu","email":"hjl.tools@gmail.com"},"content":"On Fri, Apr 3, 2026 at 8:24 PM H.J. Lu wrote:\n>\n> commit f511bf93f947199a9f9099fee87b7052e5515fb9\n> Author: H.J. Lu \n> Date: Sun Mar 29 14:30:28 2026 -0700\n>\n> x86: Call ix86_access_stack_p only for larger alignment\n>\n> has 2 issues:\n>\n> 1. It is incorrect to use GET_MODE_ALIGNMENT as memory alignment since\n> memory alignment can be different from mode alignment as in\n>\n> (set (reg:OI 20 xmm0 [orig:112 s ] [112])\n> (mem/c:OI (plus:DI (reg/f:DI 7 sp)\n> (const_int -32 [0xffffffffffffffe0])) [3 s+0 S32 A128]))\n>\n> MEM_ALIGN should be used instead.\n>\n> 2. It replaced:\n>\n> HARD_REG_SET hard_stack_slot_access = stack_slot_access;\n> ...\n> bool symbolic_const_load_p = false;\n>\n> if (!TEST_HARD_REG_BIT (hard_stack_slot_access, regno))\n> ...\n> symbolic_const_load_p = true;\n> ...\n>\n> if (!symbolic_const_load_p\n> || ix86_access_stack_p...)\n> call ix86_update_stack_alignment.\n>\n> with\n>\n> if (ix86_need_alignment_p...\n> && ix86_access_stack_p...)\n> call ix86_update_stack_alignment.\n>\n> Since ix86_access_stack_p excludes registers on hard_stack_slot_access,\n> stack alignment isn't updated for registers on hard_stack_slot_access.\n> Instead, we should do\n>\n> if (ix86_need_alignment_p...\n> && (TEST_HARD_REG_BIT (hard_stack_slot_access, regno)\n> || ix86_access_stack_p...))\n> call ix86_update_stack_alignment.\n\nThe compile times of PR target/124165 and PR target/124684 test are\nunchanged.\n\n> gcc/\n>\n> PR target/124759\n> * config/i386/i386.cc (ix86_need_alignment_p_1): Replace\n> GET_MODE_ALIGNMENT with MEM_ALIGN.\n> (ix86_find_max_used_stack_alignment): Restore\n> hard_stack_slot_access handling.\n>\n> gcc/testsuite/\n>\n> PR target/124759\n> * gcc.target/i386/pr124759.c: New test.\n>\n>\n> --\n> H.J.","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 (2048-bit key;\n unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256\n header.s=20251104 header.b=dNJk4H6K;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=gcc.gnu.org\n (client-ip=2620:52:6:3111::32; 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Fri, 03 Apr 2026\n 10:18:37 -0700 (PDT)","MIME-Version":"1.0","References":"\n ","In-Reply-To":"\n ","From":"\"H.J. Lu\" ","Date":"Sat, 4 Apr 2026 01:18:00 +0800","X-Gm-Features":"AQROBzBrnnIcLaEkNMiWJXYXZ-Hu7-LpYLZwAes5NWyOfz0e2a4b2ebBmN0sw6k","Message-ID":"\n ","Subject":"Re: [PATCH] Correct x86: Call ix86_access_stack_p only for larger\n alignment","To":"GCC Patches , Richard Biener ,\n Uros Bizjak , Hongtao Liu ","Content-Type":"text/plain; charset=\"UTF-8\"","Content-Transfer-Encoding":"quoted-printable","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"}}]