From patchwork Thu Apr 3 13:17:52 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paolo Bonzini X-Patchwork-Id: 14036893 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 39790C3600C for ; Thu, 3 Apr 2025 13:19:19 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1u0KSP-0004nL-Uy; Thu, 03 Apr 2025 09:18:10 -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 1u0KSL-0004mS-Cx for qemu-devel@nongnu.org; Thu, 03 Apr 2025 09:18:06 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1u0KSJ-0008To-Us for qemu-devel@nongnu.org; Thu, 03 Apr 2025 09:18:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1743686283; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=hK1VQdhGXr6t7dx8oFywUBtknIybBnZEBM/8ByV3isY=; b=VuESBqd8wJnoJ/IAd/zUB1Oj0H3eY+7brmV6+EA4YAgy9hdqPeUsg/X4UkWOKawxNoWqH3 ui61xhqkxMNoUv2YsdTgLrb2QRix/4p30slUJI1zoEUmT8lrcaX+lZjQd6xc506NVFDAEG 7uzIsbAm+5xQyB5hK8f0CRo5rTGykd4= Received: from mail-ej1-f70.google.com (mail-ej1-f70.google.com [209.85.218.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-111-aR9sP9goORK08A8Xqyt4jA-1; Thu, 03 Apr 2025 09:18:01 -0400 X-MC-Unique: aR9sP9goORK08A8Xqyt4jA-1 X-Mimecast-MFC-AGG-ID: aR9sP9goORK08A8Xqyt4jA_1743686280 Received: by mail-ej1-f70.google.com with SMTP id a640c23a62f3a-ac3d3cd9accso74891566b.3 for ; Thu, 03 Apr 2025 06:18:01 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1743686279; x=1744291079; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=hK1VQdhGXr6t7dx8oFywUBtknIybBnZEBM/8ByV3isY=; b=KlKJxO4BDys25CmfsPifD2kijTY2cFseJa9wxFwfHcF1dxJ2jBr2HGy9Tjwj7nsJYg t5lAVHxpt/eNUpjlTdSKG4UFuWaZzKbnReNlxVQNSLW6ZQ1EYlBqEUCwGMS1Kyfaa0Lp tm5+URUOwEiFQpvLgMBHEUBc/+TNAI/b+R5zkoT56ePu/5YpA0Sn9fDBS8VyUls2SMkX a3BjUPblDlwaMwsKw12yfZEgH04KlcTAf24Qe/TXIMlMbGiscG5Xlerg6rJKKpKVffgj 9APteBbRgHSucr67PxAsFZLqueyxiLswnyJMRURS1qfJGJJa58FcazFXDsywbnbz9Jg0 oOdQ== X-Gm-Message-State: AOJu0Yy/FemXk86S7BQ2gGI5e0cPOowF1pe8Mt+8kkrxonRhymvVHKfg NFtvObr/HGsnJB41R9VYpDbvwxbaQj+ZHEiN84Iy/bb3B7AMAcQZEyYkRDJRkAgLj72SfyFbIRM l4Rbhl0eFAoMh78E7ZXjhHYkwSnRp29i1d/oVV7OnX83xoLB1Qwu3ThrIrBB6bDKiZTnWWMJbwO yXqfiepNmVcyLMT9DALSZZFiDtCxz93RtYL17k X-Gm-Gg: ASbGncv5g5AF4z9SbOSTJqC2RlRyuVa2b7c9ij83L2rfeJ+XFOU7QLZS+mDDdfzXjIA 70fQkOwfjDL2PdQvkoXvH74RQRkWRx7yr6Cq/DVx7N2BfaSaEjqVUwQYAtduljUjJQN3llBuiLg OY2Pzt0GJfaIZ+KQaYzOPgT1H8PuedU/u4Z94PbV6v7Pkb/v+s2EBvAY55mWqjXIYBz3tmyAODH Qzhvoi/L6PJSem9719fd9s0cr3Ils2PmTLryFLyAjKoeYcb+R0RTJrW0kf5I/gTvrRa9ZKph4LP 51rDDLSm0xFqPTYSMJ3K X-Received: by 2002:a17:907:72c4:b0:ac3:8899:d2a6 with SMTP id a640c23a62f3a-ac7bc067d9bmr225038066b.12.1743686279216; Thu, 03 Apr 2025 06:17:59 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHyY9HucX6eJznLXasdmNwiAkD9tXY+fdRO7/orCYTaLAMsId1dImomE/oh5VCzXcVXfxzfJA== X-Received: by 2002:a17:907:72c4:b0:ac3:8899:d2a6 with SMTP id a640c23a62f3a-ac7bc067d9bmr225034666b.12.1743686278728; Thu, 03 Apr 2025 06:17:58 -0700 (PDT) Received: from [192.168.122.1] ([151.49.230.224]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ac7bfe61bb2sm93513966b.32.2025.04.03.06.17.57 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Apr 2025 06:17:57 -0700 (PDT) From: Paolo Bonzini To: qemu-devel@nongnu.org Subject: [PATCH 2/3] target/i386: emulate: microoptimize and explain ADD_COUT_VEC/SUB_COUT_VEC Date: Thu, 3 Apr 2025 15:17:52 +0200 Message-ID: <20250403131753.82072-3-pbonzini@redhat.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250403131753.82072-1-pbonzini@redhat.com> References: <20250403131753.82072-1-pbonzini@redhat.com> MIME-Version: 1.0 Received-SPF: pass client-ip=170.10.129.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -26 X-Spam_score: -2.7 X-Spam_bar: -- X-Spam_report: (-2.7 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.649, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, 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 The logic is the same, but the majority(NOT a, b, c) is brought out to a separate macro and implemented without NOT operations. Signed-off-by: Paolo Bonzini --- target/i386/hvf/x86_flags.c | 26 +++++++++++++++++++++----- 1 file changed, 21 insertions(+), 5 deletions(-) diff --git a/target/i386/hvf/x86_flags.c b/target/i386/hvf/x86_flags.c index 03d6de5efc3..25553bd55fd 100644 --- a/target/i386/hvf/x86_flags.c +++ b/target/i386/hvf/x86_flags.c @@ -45,14 +45,30 @@ #define LF_MASK_CF (0x01 << LF_BIT_CF) #define LF_MASK_PO (0x01 << LF_BIT_PO) +/* majority(NOT a, b, c) = (a ^ b) ? b : c */ +#define MAJ_INV1(a, b, c) ((((a) ^ (b)) & ((b) ^ (c))) ^ (c)) + +/* + * ADD_COUT_VEC(x, y) = majority((x + y) ^ x ^ y, x, y) + * + * If two corresponding bits in x and y are the same, that's the carry + * independent of the value (x+y)^x^y. Hence x^y can be replaced with + * 1 in (x+y)^x^y, resulting in majority(NOT (x+y), x, y) + */ #define ADD_COUT_VEC(op1, op2, result) \ - (((op1) & (op2)) | (((op1) | (op2)) & (~(result)))) + MAJ_INV1(result, op1, op2) +/* + * SUB_COUT_VEC(x, y) = NOT majority(x, NOT y, (x - y) ^ x ^ NOT y) + * = majority(NOT x, y, (x - y) ^ x ^ y) + * + * Note that the carry out is actually a borrow, i.e. it is inverted. + * If two corresponding bits in x and y are different, the value that + * the bit has in (x-y)^x^y likewise does not Hence x^y can be replaced + * with 0 in (x-y)^x^y, resulting in majority(NOT x, y, x-y) + */ #define SUB_COUT_VEC(op1, op2, result) \ - (((~(op1)) & (op2)) | (((~(op1)) ^ (op2)) & (result))) - -#define GET_ADD_OVERFLOW(op1, op2, result, mask) \ - ((((op1) ^ (result)) & ((op2) ^ (result))) & (mask)) + MAJ_INV1(op1, op2, result) /* ******************* */ /* OSZAPC */