From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 960343FBEAF for ; Fri, 17 Jul 2026 13:22:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784294538; cv=none; b=uz5Ywt5w0gbdkQF+WVPmWoAp+/1P+zyenIzFYAEDi4f6Wy0IB+3xwLlmLNlDSoSrzZux2h0mFxgFU4ddjubG6xbeEjsA0AIniXRYYaCUH5RHOnKBnkjK0D6tD6hXYNi3NqGPz704r3AVw1sEZZqYnRxMHYk6/HAP9rCwvj7TnjU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784294538; c=relaxed/simple; bh=ZpoCI9ofx2p/ua+KhEMRhGi82OXdAYlebI0ztnF7GEI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=oNtqnyyoMf5dd6iKx6KIuigUgnuGnxylTKmfSbrdaBbMD8MgSo5b/AHb4HbsHevGbSAVzNqUrjiCvxEFQ7uEkaZ64Le0jN81ltvXXWvoWihx7nY4chZmguDc0tJbjYIbjP0ZTtCxext5cy31dYIdg0yl9YugZ7dUIbCgBoM0mxs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=K6AyEy3S; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="K6AyEy3S" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 6F3231476; Fri, 17 Jul 2026 06:22:11 -0700 (PDT) Received: from J2N7QTR9R3 (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 060EE3F7D8; Fri, 17 Jul 2026 06:22:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1784294535; bh=ZpoCI9ofx2p/ua+KhEMRhGi82OXdAYlebI0ztnF7GEI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=K6AyEy3StxJcwPLr/m61NkJzXizkRu07Wyuz+kg41HvvKbPRzZqm+z8Wm0ev8hoxp OyjIi/WvIUkh3uwZOORa4hYvZ6Idk9ltbu1Ve2kAUkf/IiuFVW4JH1CDAgs8CstcX0 KFIJXYHoTIb3Gq6WTIH4HCNgywrD0MHc3LdKI6H4= Date: Fri, 17 Jul 2026 14:22:07 +0100 From: Mark Rutland To: Vladimir Murzin Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, broonie@kernel.org, catalin.marinas@arm.com, james.morse@arm.com, maz@kernel.org, oupton@kernel.org, tabba@google.com, will@kernel.org Subject: Re: [PATCH 17/18] arm64: fpsimd: Move SME save/restore inline Message-ID: References: <20260521132556.584676-1-mark.rutland@arm.com> <20260521132556.584676-18-mark.rutland@arm.com> <08e5ce52-be74-4fc5-a0b2-8f405a5eff99@arm.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, May 29, 2026 at 10:10:35AM +0100, Mark Rutland wrote: > On Tue, May 26, 2026 at 05:38:40PM +0100, Mark Rutland wrote: > > On Tue, May 26, 2026 at 04:28:17PM +0100, Mark Rutland wrote: > > > On Tue, May 26, 2026 at 03:39:56PM +0100, Vladimir Murzin wrote: > > > > I suspect you are intentionally not using "Ucj" constrain to limit register allocator, > > > > if so I'm wondering why? > > > > > > Thanks for the suggestion; that was ignorance rather than intent. > > > > > > I was not aware of "Ucj" as it doesn't appear on the public GCC > > > documentation: > > > > > > https://gcc.gnu.org/onlinedocs/gcc/Machine-Constraints.html > > > > > > Looking at the machine description file, that's marked with '@internal', > > > so IIUC GCC folk don't seem to expect/want people to use it. That said, > > > LLVM seems to support it. > > > > > > I'll go check that all relevant toolchains support this, and poke GCC > > > folk to see if they're happy to promote that to a public constraint. > > > > GCC folk seem happy to make this public, which is great! I'll cross-link > > a thread here if/when patches appear. > > Alex Coplan sent a patch for GCC to make this public: > > https://gcc.gnu.org/pipermail/gcc-patches/2026-May/718560.html Just for posterity, that was merged in GCC commit: 090f3e78a10b5ce14fd80de82d3e8dda8af1cae6 ("aarch64: Make Uc[ij] constraints public") ... which can be found at: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=090f3e78a10b5ce14fd80de82d3e8dda8af1cae6 ... so we should be able to use that in future once our minimum supported toolchains are GCC 14.1.0+ and and LLVM 18.1.0+. Mark.