[{"id":3628905,"web_url":"http://patchwork.ozlabs.org/comment/3628905/","msgid":"","list_archive_url":null,"date":"2025-12-26T22:35:52","subject":"Re: [PATCH] simplify-rtx: Fix up (ne (ior (ne x 0) y) 0)\n simplification [PR123114]","submitter":{"id":81263,"url":"http://patchwork.ozlabs.org/api/people/81263/","name":"Jeffrey Law","email":"jeffreyalaw@gmail.com"},"content":"On 12/15/2025 1:50 AM, Jakub Jelinek wrote:\n> Hi!\n>\n> The following testcase ICEs on x86_64-linux since the PR52345\n> (ne (ior (ne x 0) y) 0) simplification was (slightly) fixed.\n> It wants to optimize\n> (set (reg/i:DI 10 a0)\n> (ne:DI (ior:DI (ne:DI (reg:DI 151 [ a ])\n> (const_int 0 [0]))\n> (reg:DI 152 [ b ]))\n> (const_int 0 [0])))\n> but doesn't check important property of that, in particular\n> that the mode of the inner NE operand is the same as the\n> mode of the inner NE.\n> The following testcase has\n> (set (reg:CCZ 17 flags)\n> (compare:CCZ (ior:QI (ne:QI (reg/v:SI 104 [ c ])\n> (const_int 0 [0]))\n> (reg:QI 98 [ _5 ]))\n> (const_int 0 [0])))\n> where cmp_mode is QImode, but the mode of the inner NE operand\n> is SImode instead, and it attempts to create\n> (ne:CCZ (ior:QI (reg/v:SI 104 [ c ]) (reg:QI 98 [ _5 ])) (const_int 0))\n> which obviously crashes later on.\n>\n> The following patch fixes it by checking the mode of the inner NE operand\n> and also by using CONST0_RTX (cmp_mode) instead of CONST0_RTX (mode)\n> because that is the mode of the other operand, not mode which is the\n> mode of the outer comparison (though, guess for most modes it will still\n> be const0_rtx).\n>\n> I guess for mode mismatches we could arbitrarily choose some extension (zero\n> or sign) and extend the narrower mode to the wider mode, but I doubt that it\n> would ever match on any target. But even then we'd need to limit it, we\n> wouldn't want to deal with another mode class (say floating point\n> comparisons), and dunno about vector modes etc.\n>\n> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?\n>\n> 2025-12-13 Jakub Jelinek \n>\n> \tPR rtl-optimization/123114\n> \t* simplify-rtx.cc (simplify_context::simplify_relational_operation):\n> \tVerify XEXP (XEXP (op0, 0), 0) mode and use CONST0_RTX (cmp_mode)\n> \tinstead of CONST0_RTX (mode).\n>\n> \t* gcc.dg/pr123114.c: New test.\n\nOK.  And, no I don't think it would ever match either, so handling \nmismatches seems like it's an effort with zero gain.\n\n\njeff","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=20230601 header.b=RqeGJbqd;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=gcc.gnu.org\n (client-ip=38.145.34.32; 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