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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (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 46475CD3427 for ; Tue, 5 May 2026 15:58:45 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [127.0.0.1]) by lists.ozlabs.org (Postfix) with ESMTP id 4g938g5Smlz2xfB; Wed, 06 May 2026 01:58:43 +1000 (AEST) Authentication-Results: lists.ozlabs.org; arc=none smtp.remote-ip=63.228.1.57 ARC-Seal: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1777996723; cv=none; b=KS1azfh1NN09/5bgDnaflplzWbA3+rrq+srpwzqkcwUNqIyj1NLe8iaOL3yz7pQkhno/gD4lQdJmIm2a0csFXv0Pa1hnW1QkDsB6L8XgFzEaZeYVE6pKKftkhV8GGZpIdYYbJqeD0bXm28YQKQw9ylqKeyYJltsUVl1c6OYMzuRS/CZDjWpO7lIk8KUtajk6cDGihVZsrBa7uWlvcn0sVV84xK13W1q3vLJZ3RbcW+fOW/oLv9vaBlSaFEN8V+hsMDufDD57lNJlqQdQ73G4LVU3ZJnBo7KNVRPB4ptrVnTWn+zOfz1bIx7fMs6HJp6eOfhMPJvl5Sgp0ySMV0gexw== ARC-Message-Signature: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1777996723; c=relaxed/relaxed; bh=rSFnuj2S2pOktYS6KR8pu0EM6XWflOBaN/tj/8NJgMk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=NFNjg/pJx6AKr5m9tF5kJcNGKeoyiq2MMaEmovSD0mhqJVrgi3lmErRTVKD7zMHsyxpvDrpft89VAYQ1NFaK8jitUEYCpdaeOJy7t3ewOdKkDvSE6D0NoqNzxSlEj2JRYVJSGBpnJ5nldJcJq35+EkjbV7NXw8Yn7/ULhSmTnA58OtCy86B/GuIdONGKxZuNOMLWJXwmXKQb2cKEzUn9TL7hyVBQOcac1PgrFLtNlQc4eu7cwjWeFTtRPAzEr0MKZSWiU0ODP78Yg3SulQtKQCTCY155rSQJIfvxM7aWPaLR0LxezHDtIeTVc8SScyy/Y6dHqwUVY9fj/f0BgXFSqg== ARC-Authentication-Results: i=1; lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org; spf=pass (client-ip=63.228.1.57; helo=gate.crashing.org; envelope-from=segher@kernel.crashing.org; receiver=lists.ozlabs.org) smtp.mailfrom=kernel.crashing.org Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kernel.crashing.org (client-ip=63.228.1.57; helo=gate.crashing.org; envelope-from=segher@kernel.crashing.org; receiver=lists.ozlabs.org) Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) by lists.ozlabs.org (Postfix) with ESMTP id 4g938f0JHPz2xMV for ; Wed, 06 May 2026 01:58:41 +1000 (AEST) Received: from gate.crashing.org (localhost [127.0.0.1]) by gate.crashing.org (8.18.1/8.18.1/Debian-2) with ESMTP id 645Fv4oO164706; Tue, 5 May 2026 10:57:04 -0500 Received: (from segher@localhost) by gate.crashing.org (8.18.1/8.18.1/Submit) id 645Fuwtk164700; Tue, 5 May 2026 10:56:58 -0500 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Tue, 5 May 2026 10:56:58 -0500 From: Segher Boessenkool To: Peter Zijlstra Cc: Sathvika Vasireddy , nathan@kernel.org, nsc@kernel.org, maddy@linux.ibm.com, mpe@ellerman.id.au, npiggin@gmail.com, chleroy@kernel.org, jpoimboe@kernel.org, ojeda@kernel.org, masahiroy@kernel.org, lossin@kernel.org, tamird@kernel.org, thomas.weissschuh@linutronix.de, rostedt@goodmis.org, ihor.solodrai@linux.dev, thuth@redhat.com, pmladek@suse.com, aliceryhl@google.com, elver@google.com, kees@kernel.org, legion@kernel.org, ardb@kernel.org, yuxuan.zuo@outlook.com, alexghiti@rivosinc.com, alexandre.chartre@oracle.com, bp@alien8.de, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH v1 1/6] objtool/powerpc: Add build-time fixup of alternate feature branch targets Message-ID: References: <20260505084628.17940-1-sv@linux.ibm.com> <20260505084628.17940-2-sv@linux.ibm.com> <20260505144539.GX3126523@noisy.programming.kicks-ass.net> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260505144539.GX3126523@noisy.programming.kicks-ass.net> Hi! On Tue, May 05, 2026 at 04:45:39PM +0200, Peter Zijlstra wrote: > On Tue, May 05, 2026 at 02:16:23PM +0530, Sathvika Vasireddy wrote: > > switch (opcode) { > > + case 16: > > Like case 18 below, this wants a comment describing which instruction > this is; bclr ? Yes. It is 19/16, b[c]lr (primary opcode 19, secondary opcode 16). Where is it described what INSN_RETURN actually means for objtool? Not in the header file :-( For PowerPC, all three of b[c]lr[l], b[c]ctr[l], and b[c]tar[l] are indirect jumps, to an address in a register. They do absolutely nothing typically done in a function epilog, like "return" insns in some other archs do. But the BH field ("branch hint") in the instruction helps predict the control flow involving the insn as something in a call and return pattern :-) Segher