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 X-Spam-Level: X-Spam-Status: No, score=-5.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A9C0CC433F5 for ; Wed, 22 Sep 2021 15:17:35 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 6DCE2611B0 for ; Wed, 22 Sep 2021 15:17:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 6DCE2611B0 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=xen0n.name Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:58012 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mT406-0001Vw-Iu for qemu-devel@archiver.kernel.org; Wed, 22 Sep 2021 11:17:34 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:60044) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mT3yv-0008R1-0x for qemu-devel@nongnu.org; Wed, 22 Sep 2021 11:16:21 -0400 Received: from [115.28.160.31] (port=38440 helo=mailbox.box.xen0n.name) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mT3yq-00063v-V9 for qemu-devel@nongnu.org; Wed, 22 Sep 2021 11:16:20 -0400 Received: from [192.168.9.172] (unknown [101.88.29.172]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits)) (No client certificate requested) by mailbox.box.xen0n.name (Postfix) with ESMTPSA id 210F1633F2; Wed, 22 Sep 2021 23:16:07 +0800 (CST) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=xen0n.name; s=mail; t=1632323767; bh=ixEjrV654ri/mXiUZn0tllL4e/hK0kkqMlYBNC2VJVo=; h=Date:Subject:To:References:From:In-Reply-To:From; b=OFwGP8+Xy4kbifIx7PvqJE2FeOJ06UA7/leR3PFayEYOa+eZKNQFmIjy3VR3IKLXF PRQhKQHUzKl5EA4vsGCkvTbunbVAlYSvGdz+5SoKakZrF9FpKoOtgkr77o8PQUJRaX 8pZxvpU8mQNfJd+47tFsFJ4Q41zcsBfZnnxFBEQo= Message-ID: <75621c34-5cf8-3ae9-86cf-ce3cf53b4669@xen0n.name> Date: Wed, 22 Sep 2021 23:16:06 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:94.0) Gecko/20100101 Thunderbird/94.0a1 Subject: Re: [PATCH v2 09/30] tcg/loongarch64: Implement tcg_out_mov and tcg_out_movi Content-Language: en-US To: Richard Henderson , qemu-devel@nongnu.org References: <20210921201915.601245-1-git@xen0n.name> <20210921201915.601245-10-git@xen0n.name> <0717a7de-7c41-990d-ec7a-51b44f49724e@linaro.org> From: WANG Xuerui In-Reply-To: <0717a7de-7c41-990d-ec7a-51b44f49724e@linaro.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Host-Lookup-Failed: Reverse DNS lookup failed for 115.28.160.31 (failed) Received-SPF: pass client-ip=115.28.160.31; envelope-from=i.qemu@xen0n.name; helo=mailbox.box.xen0n.name X-Spam_score_int: -12 X-Spam_score: -1.3 X-Spam_bar: - X-Spam_report: (-1.3 / 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, NICE_REPLY_A=-0.001, RDNS_NONE=0.793, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hi Richard, On 9/22/21 12:25, Richard Henderson wrote: > On 9/21/21 1:18 PM, WANG Xuerui wrote: >> +    /* Test for PC-relative values that can be loaded faster.  */ >> +    intptr_t pc_offset = val - (uintptr_t)s->code_ptr; > > This isn't quite right for split r^x code buffer. > You should have seen this with --enable-debug-tcg... > > You need pc_offset = tcg_pcrel_diff(s, (void *)val). Indeed; I just realized TCG debugging isn't fully enabled with --enable-debug only. Will fix in v3. > >> +    if (pc_offset == (int32_t)pc_offset) { >> +        tcg_target_long lo = sextreg(pc_offset, 0, 12); >> +        tcg_target_long hi = pc_offset - lo; >> +        tcg_out_opc_pcaddu12i(s, rd, hi >> 12); > > And... this doesn't quite work, right at the edges.  If lo is > negative, hi can overflow out of range.  There are a number of ways to > fix this.  One is to extract the pieces and re-assemble to see if it > matches.  Another is to rearrange the arithmetic just a little and use > PCALAU12I. I actually wrote a small test program to test for this, but found no overflow issues here; rather the tcg_out_opc_ori call below has signedness problem (need to mask the low variable, which is signed, with 0xfff to avoid overwriting the opcode field). I think I'll add a tcg_debug_assert here, but keep the logic intact. > >> +    tcg_target_long upper = (val >> 12) & 0xfffff; >> +    tcg_target_long higher = (val >> 32) & 0xfffff; > > Better to use extract64(val, 12, 20) and extract64(val, 32, 30). Sure; but as the instructions perform sign-extension, thus taking signed operands, sextract64 or the wrapped sextreg will do it. > > > r~