From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 754E2CD342C for ; Wed, 6 May 2026 15:37:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=rsfzxlWlUfAtZGI+qAXkjznTjniwrhyCHyN/kFIVlaQ=; b=tdeA8o3jLcix5RIJMW4AWsi49W IEoOcoCdEYNjo2kwCjnbzwxgvse5dNAlZSN2qCqkvnUNoFQ4lIDJdvegDp3KhxAnSU2/DvkJLAje4 i8gQFJaFcUgi5Yjfh+7vKdy1iuKi/BqsoFK3+aSV5JVqQjqhxDLEK5S8zF8wq79Wrvmb4WaLhD9XH sGm+AGWqyv5HJPvqO02hTAgoFQMTXq+VcQQZv9cBxp8jouqDui3WpIbXD/GBuNBRM09A/X+NqG4NY J4M/06OcV5pCAKD4MLrlNg1dhp2Xo5G/A41ABmpw5mcr3FMKFF1cqkmHVKbB4vscmUhKVR5ais6pp Jwahac1Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wKeJC-00000001MWM-2LXs; Wed, 06 May 2026 15:37:10 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wKeJA-00000001MVf-39sN; Wed, 06 May 2026 15:37:08 +0000 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 67E5B1682; Wed, 6 May 2026 08:37:01 -0700 (PDT) Received: from arm.com (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 923CB3F7B4; Wed, 6 May 2026 08:37:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1778081826; bh=5jyzOt/YE4MAJ87a+6OW9BOIOtlHnKUUXQbFsJ69GA8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=bMdi+zP3Eg/uLU1d3mO63YYr4BA3ZO4t1algcuI4CFGs8XeA9T34+qb0rdR39jzeg j06elKg2k5eNJF+ZUZm4HfbXrZgBVCdvHX1pcaN+Q7kkJVmt6743pZjHTA/47tQcPO EhPeVMH+7RxtBnh++b/ct/abuXYH8cT/M2HIAXHg= Date: Wed, 6 May 2026 16:37:01 +0100 From: Catalin Marinas To: K Prateek Nayak Cc: Thomas Gleixner , Ingo Molnar , Peter Zijlstra , Sebastian Andrzej Siewior , Will Deacon , Darren Hart , Davidlohr Bueso , =?iso-8859-1?Q?Andr=E9?= Almeida , linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, linux-riscv@lists.infradead.org, linux-arm-kernel@lists.infradead.org, Jisheng Zhang Subject: Re: [PATCH v4 3/8] arm64/runtime-const: Introduce runtime_const_mask_32() Message-ID: References: <20260430094730.31624-1-kprateek.nayak@amd.com> <20260430094730.31624-4-kprateek.nayak@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260430094730.31624-4-kprateek.nayak@amd.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260506_083708_838909_F11B381E X-CRM114-Status: GOOD ( 10.63 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Apr 30, 2026 at 09:47:25AM +0000, K Prateek Nayak wrote: > Futex hash computation requires a mask operation with read-only after > init data that will be converted to a runtime constant in the subsequent > commit. > > Introduce runtime_const_mask_32 to further optimize the mask operation > in the futex hash computation hot path. GCC generates a: > > movz w1, #lo16, lsl #0 // w1 = bits [15:0] > movk w1, #hi16, lsl #16 // w1 = full 32-bit value > and w0, w0, w1 // w0 = w0 & w1 > > pattern to tackle arbitrary 32-bit masks and the same was also suggested > by Claude which is implemented here. The final (__ret & mask) operation > is intentiaonally placed outside of asm block to allow compilers to > further optimize it if possible. > > __runtime_fixup_ptr() already patches a "movz, + movk lsl #16" sequence > which has been reused to patch the same sequence for > __runtime_fixup_mask(). > > Assisted-by: Claude:claude-sonnet-4-5 > Signed-off-by: K Prateek Nayak Reviewed-by: Catalin Marinas