From patchwork Wed Mar 1 14:22:21 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Anton Johansson X-Patchwork-Id: 13156061 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.gnu.org (lists.gnu.org [209.51.188.17]) (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 9D066C6FA9D for ; Wed, 1 Mar 2023 14:23:07 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pXNM0-0000Iu-JG; Wed, 01 Mar 2023 09:22:50 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pXNLp-0008Pj-M4 for qemu-devel@nongnu.org; Wed, 01 Mar 2023 09:22:38 -0500 Received: from rev.ng ([5.9.113.41]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pXNLo-0000r4-1l for qemu-devel@nongnu.org; Wed, 01 Mar 2023 09:22:37 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=rev.ng; s=dkim; h=Content-Transfer-Encoding:MIME-Version:Message-Id:Date:Subject:Cc: To:From:Sender:Reply-To:Content-Type:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: In-Reply-To:References:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=+I4qRuHciEfRJecQBuQQhrSG2K8AU8/5R1o5v8ket0E=; b=pw/Zh94zK1E3TxEbRIaJ0acQun U9/pqPJDIZE9uKoy/f9m4GfeFdUpFDslKGbwDjA+21kGI5N2cbFpa31zFKLlA/qeO+QSOja9g0W+B JJP/H9zdXcXh0xKkY7Q/CAHvqAdGAezZHhJVfUYcjiMq/qvSj1ZG1B7oAgiM0Mj2OpFI=; To: qemu-devel@nongnu.org Cc: ale@rev.ng, richard.henderson@linaro.org, tsimpson@quicinc.com Subject: [PATCH] tcg: `reachable_code_pass()` remove empty else-branch Date: Wed, 1 Mar 2023 15:22:21 +0100 Message-Id: <20230301142221.24495-1-anjo@rev.ng> MIME-Version: 1.0 Received-SPF: pass client-ip=5.9.113.41; envelope-from=anjo@rev.ng; helo=rev.ng X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-to: Anton Johansson X-Patchwork-Original-From: Anton Johansson via From: Anton Johansson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org This patch extends reachable_code_pass() to also deal with empty else-branches of the form br $L0 set_label $L1 set_label $L0 converting them to set_label $L1 when $L0 is only referenced by the br op. This type of empty-else branch will be emitted by idef-parser in the Hexagon frontend once CANCEL statements have been ignored. Signed-off-by: Anton Johansson --- tcg/tcg.c | 41 ++++++++++++++++++++++++++++++----------- 1 file changed, 30 insertions(+), 11 deletions(-) -- 2.39.1 diff --git a/tcg/tcg.c b/tcg/tcg.c index a4a3da6804..531bc74231 100644 --- a/tcg/tcg.c +++ b/tcg/tcg.c @@ -2664,21 +2664,40 @@ static void reachable_code_pass(TCGContext *s) dead = false; remove = false; - /* - * Optimization can fold conditional branches to unconditional. - * If we find a label with one reference which is preceded by - * an unconditional branch to it, remove both. This needed to - * wait until the dead code in between them was removed. - */ - if (label->refs == 1) { - TCGOp *op_prev = QTAILQ_PREV(op, link); - if (op_prev->opc == INDEX_op_br && - label == arg_label(op_prev->args[0])) { + TCGOp *op_prev = QTAILQ_PREV(op, link); + if (label->refs == 1 && + op_prev->opc == INDEX_op_br && + label == arg_label(op_prev->args[0])) { + /* + * Optimization can fold conditional branches to + * unconditional. If we find a label with one reference + * which is preceded by an unconditional branch to it, + * remove both. This needed to wait until the dead code + * in between them was removed. + */ + tcg_op_remove(s, op_prev); + remove = true; + } else if (op_next->opc == INDEX_op_set_label) { + /* + * The Hexagon frontend can generate empty else-branches for + * certain instructions. If we encounter + * + * br $L0 + * set_label $L1 + * set_label $L0 + * + * where $L0 only has a single reference, remove the branch + * to $L0 and the corresonding label. + */ + TCGLabel *next_label = arg_label(op_next->args[0]); + if (next_label->refs == 1 && + op_prev->opc == INDEX_op_br && + next_label == arg_label(op_prev->args[0])) { tcg_op_remove(s, op_prev); - remove = true; } } } + break; case INDEX_op_br: