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.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 241BDEE49A3 for ; Tue, 22 Aug 2023 17:23:15 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qYV5m-0002l1-0A; Tue, 22 Aug 2023 13:22:58 -0400 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 1qYV5d-0002i6-Ki for qemu-devel@nongnu.org; Tue, 22 Aug 2023 13:22:49 -0400 Received: from mail-wm1-x32b.google.com ([2a00:1450:4864:20::32b]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1qYV5b-0006ey-58 for qemu-devel@nongnu.org; Tue, 22 Aug 2023 13:22:49 -0400 Received: by mail-wm1-x32b.google.com with SMTP id 5b1f17b1804b1-3fee600dce6so31512925e9.1 for ; Tue, 22 Aug 2023 10:22:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1692724964; x=1693329764; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=Pew9QlFygzIit3zZO/KL++py1uZpNTLt5wxOEtYy9f4=; b=t2gjY1f9S9q2x6L6y0AwzQk1aWXfOjzjvIzBGJANK5fXeHs3LExKip2luO+8mBVuu9 W3ZuifNd4H8zq5rkf4vvzUfcN/46bmrsnCft6qlIt+ZAT04mR6LZrlt7Od/3i0OLHf6/ exsPmWrRSYKoo7M18bkT9j+Ezh6zJfSSjcKN6YCPRv34YZEy0E81shkHxZrmuRXZvAew xh8eXCfdKI2c3Qj5OhMDnnMNXzI/cZ2kmCQ9PaDU19Og35pg7kxblDrWWwJdw1lQPfb9 3quN0e5LO8s0gmsxMhhVVaRVfRx+pq7hImAxqkU2Cvv9Fhn6lAQjAS+zbvRq+leLJxv7 B0UA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1692724964; x=1693329764; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=Pew9QlFygzIit3zZO/KL++py1uZpNTLt5wxOEtYy9f4=; b=g1mOE8Sg4Dd1F0HEM7ehutpOiEiMkl03q+tGBFwKZ2r8mZKJZB2CilaCSK+q0K9uG5 XA15ff9I9uNXaigNeDR06JiusNk4smKv37rr9eyW/IXfgcQGoY+zbLk3z6IF5lI+qBe7 2x1W+0PAn2TyJ1Ie1SR6sOLhLwzJwQAiLyegJnn095nJCAMVpyCO7ISNcdbXCpxgM/6N Vf752e45YJVcab6+1tb69DhtqY81eihIScBymM1jgfLuW1SkCVhLyT/kJb52QbGD/hwj uHwd9hfcprQaDvfXKmjCuiocubKidgIc8YS7i5mde2fJgPKfBk1FwDC35CIMRR1tTuLP UoeA== X-Gm-Message-State: AOJu0YydBtciUwpRiAsjyaEik0j+catpI091zVtZqcmG0e+Rof6oorvQ vSe+U0HFXM2aSqmMfWSPmA60wY4dURRNTN56UbxHNg== X-Google-Smtp-Source: AGHT+IFceesgF3OcRhIsGAzIgNoe/U7dQzZ8Mh8USWN9SrmD0/3QpLNURr+lI5cNKHrw4hhdaZyMQA== X-Received: by 2002:a7b:ca50:0:b0:3fe:1cd8:acf3 with SMTP id m16-20020a7bca50000000b003fe1cd8acf3mr7812134wml.17.1692724964016; Tue, 22 Aug 2023 10:22:44 -0700 (PDT) Received: from [10.2.0.2] ([37.19.214.4]) by smtp.gmail.com with ESMTPSA id u12-20020adff88c000000b003198a9d758dsm16484298wrp.78.2023.08.22.10.22.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 22 Aug 2023 10:22:43 -0700 (PDT) Message-ID: <09f4ba68-e7f3-8a90-e996-e475b760c64a@linaro.org> Date: Tue, 22 Aug 2023 19:22:41 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.14.0 Subject: Re: [PATCH 1/7] tcg/tcg-op: Document bswap16() byte pattern Content-Language: en-US To: Richard Henderson , qemu-devel@nongnu.org Cc: "Edgar E. Iglesias" , Paolo Bonzini References: <20230822093712.38922-1-philmd@linaro.org> <20230822093712.38922-2-philmd@linaro.org> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2a00:1450:4864:20::32b; envelope-from=philmd@linaro.org; helo=mail-wm1-x32b.google.com X-Spam_score_int: -38 X-Spam_score: -3.9 X-Spam_bar: --- X-Spam_report: (-3.9 / 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=-1.767, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 22/8/23 17:58, Richard Henderson wrote: > On 8/22/23 02:37, Philippe Mathieu-Daudé wrote: >> Signed-off-by: Philippe Mathieu-Daudé >> --- >>   tcg/tcg-op.c | 48 ++++++++++++++++++++++++++++++++---------------- >>   1 file changed, 32 insertions(+), 16 deletions(-) >> >> diff --git a/tcg/tcg-op.c b/tcg/tcg-op.c >> index 7aadb37756..f164ddc95e 100644 >> --- a/tcg/tcg-op.c >> +++ b/tcg/tcg-op.c >> @@ -1021,6 +1021,13 @@ void tcg_gen_ext16u_i32(TCGv_i32 ret, TCGv_i32 >> arg) >>       } >>   } >> +/* >> + * bswap16_i32: 16-bit byte swap on the low bits of a 32-bit value. >> + * >> + * Byte pattern:  bswap16_i32(xxab) -> ..ba             (TCG_BSWAP_OZ) >> + *                bswap16_i32(xxab) -> ssba             (TCG_BSWAP_OS) >> + *                bswap16_i32(xxab) -> xxba >> + */ > > Don't forget TCG_BSWAP_IZ, which means the input is already zero-extended. > Which makes > >> +                                            /* arg = xxab */ >> +        tcg_gen_shri_i32(t0, arg, 8);       /*  t0 = .xxa */ > > this > >>           if (!(flags & TCG_BSWAP_IZ)) { >> -            tcg_gen_ext8u_i32(t0, t0); >> +            tcg_gen_ext8u_i32(t0, t0);      /*  t0 = ...a */ >>           } >>           if (flags & TCG_BSWAP_OS) { >> -            tcg_gen_shli_i32(t1, arg, 24); >> -            tcg_gen_sari_i32(t1, t1, 16); >> +            tcg_gen_shli_i32(t1, arg, 24);  /*  t1 = b... */ >> +            tcg_gen_sari_i32(t1, t1, 16);   /*  t1 = ssb. */ >>           } else if (flags & TCG_BSWAP_OZ) { >> -            tcg_gen_ext8u_i32(t1, arg); >> -            tcg_gen_shli_i32(t1, t1, 8); >> +            tcg_gen_ext8u_i32(t1, arg);     /*  t1 = ...b */ >> +            tcg_gen_shli_i32(t1, t1, 8);    /*  t1 = ..b. */ >>           } else { >> -            tcg_gen_shli_i32(t1, arg, 8); >> +            tcg_gen_shli_i32(t1, arg, 8);   /*  t1 = xab. */ > > and this slightly inaccurate. > >>           } >> -        tcg_gen_or_i32(ret, t0, t1); >> +        tcg_gen_or_i32(ret, t0, t1);        /* ret = ssba */ > > This one is just confusing, since each of the three cases above have > different outputs. Is that formatting OK with you? /* * bswap16_i32: 16-bit byte swap on the low bits of a 32-bit value. * * Byte pattern: bswap16_i32(..ab) -> ..ba (TCG_BSWAP_IZ) * bswap16_i32(xxab) -> ..ba (TCG_BSWAP_OZ) * bswap16_i32(xxab) -> ssba (TCG_BSWAP_OS) * bswap16_i32(xxab) -> xxba */ void tcg_gen_bswap16_i32(TCGv_i32 ret, TCGv_i32 arg, int flags) { /* Only one extension flag may be present. */ tcg_debug_assert(!(flags & TCG_BSWAP_OS) || !(flags & TCG_BSWAP_OZ)); if (TCG_TARGET_HAS_bswap16_i32) { tcg_gen_op3i_i32(INDEX_op_bswap16_i32, ret, arg, flags); } else { TCGv_i32 t0 = tcg_temp_ebb_new_i32(); TCGv_i32 t1 = tcg_temp_ebb_new_i32(); /* arg = xxab (IZ=0) */ /* ..ab (IZ=1) */ tcg_gen_shri_i32(t0, arg, 8); /* t0 = .xxa (IZ=0) */ /* ...a (IZ=1) */ if (!(flags & TCG_BSWAP_IZ)) { tcg_gen_ext8u_i32(t0, t0); /* t0 = ...a */ } if (flags & TCG_BSWAP_OS) { tcg_gen_shli_i32(t1, arg, 24); /* t1 = b... */ tcg_gen_sari_i32(t1, t1, 16); /* t1 = ssb. */ } else if (flags & TCG_BSWAP_OZ) { tcg_gen_ext8u_i32(t1, arg); /* t1 = ...b */ tcg_gen_shli_i32(t1, t1, 8); /* t1 = ..b. */ } else { tcg_gen_shli_i32(t1, arg, 8); /* t1 = xab. (IZ=0) */ /* .ab. (IZ=1) */ } tcg_gen_or_i32(ret, t0, t1); /* ret = ..ba (IZ=1 or OZ=1) */ /* = ssba (OS=1) */ /* = xxba (no flag) */ tcg_temp_free_i32(t0); tcg_temp_free_i32(t1); } } ---