From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH] x86 emulator: Add call near absolute instruction (group5: opcode 0xff mod r/m 2) Date: Wed, 10 Sep 2008 10:29:44 +0300 Message-ID: <48C77768.8050001@qumranet.com> References: <20080908184719.GB31824@mohd-laptop> <20080909091622.7cbb4ff5@frecb000711> <48C68D57.9020105@qumranet.com> <52d4a3890809091005y6291d3e8sc8bd5b151255b002@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Guillaume Thouvenin , kvm@vger.kernel.org To: Mohammed Gamal Return-path: Received: from il.qumranet.com ([212.179.150.194]:21798 "EHLO il.qumranet.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751049AbYIJH3k (ORCPT ); Wed, 10 Sep 2008 03:29:40 -0400 In-Reply-To: <52d4a3890809091005y6291d3e8sc8bd5b151255b002@mail.gmail.com> Sender: kvm-owner@vger.kernel.org List-ID: Mohammed Gamal wrote: >> >> SrcAcc would remove the need for this change. >> >> > > Stupid question: What does Acc stand for? :) > Accumulator (al/ax/eax/rax). In the good old days cpus would have only one register that was able to fully participate in arithmetic operations, typically called A for Accumulator. The x86 retains this tradition by having special, shorter encodings for the A register (like the cmp opcode), and even some instructions that only operate on A (like mul). SrcAcc and DstAcc would accommodate these instructions by decoding A into the corresponding 'struct operand'. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.