https://wenyiblog.top/tags/%E5%86%85%E5%AD%98%E8%AE%BF%E9%97%AE/ Recent content in 内存访问 on 文艺技术笔记 Hugo -- gohugo.io zh 文艺技术笔记 | 软件工程师文艺 Sat, 13 Jun 2026 10:00:00 +0800 https://wenyiblog.top/2026/06/asm-06-addressing-modes/ Sat, 13 Jun 2026 10:00:00 +0800 https://wenyiblog.top/2026/06/asm-06-addressing-modes/ <h2 id="寻址的本质"><a href="#%e5%af%bb%e5%9d%80%e7%9a%84%e6%9c%ac%e8%b4%a8" class="header-anchor"></a>寻址的本质 </h2><p>CPU 执行指令时，需要找到操作数的位置。<strong>寻址方式</strong>就是告诉 CPU 去哪里找数据。</p> <h2 id="立即数寻址"><a href="#%e7%ab%8b%e5%8d%b3%e6%95%b0%e5%af%bb%e5%9d%80" class="header-anchor"></a>立即数寻址 </h2><p>数据直接在指令中：</p> <div class="highlight"><div class="chroma"> <table class="lntable"><tr><td class="lntd"> <pre tabindex="0" class="chroma"><code><span class="lnt">1 </span></code></pre></td> <td class="lntd"> <pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">MOV AX, 1234h </span></span></code></pre></td></tr></table> </div> </div><ul> <li>最快，无需访问内存</li> <li>数据随指令一起从代码段取出</li> </ul> <h2 id="寄存器寻址"><a href="#%e5%af%84%e5%ad%98%e5%99%a8%e5%af%bb%e5%9d%80" class="header-anchor"></a>寄存器寻址 </h2><p>操作数在寄存器中：</p> <div class="highlight"><div class="chroma"> <table class="lntable"><tr><td class="lntd"> <pre tabindex="0" class="chroma"><code><span class="lnt">1 </span></code></pre></td> <td class="lntd"> <pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">MOV AX, BX </span></span></code></pre></td></tr></table> </div> </div><ul> <li>极快，寄存器在 CPU 内部</li> <li>无内存访问延迟</li> </ul> <h2 id="直接寻址"><a href="#%e7%9b%b4%e6%8e%a5%e5%af%bb%e5%9d%80" class="header-anchor"></a>直接寻址 </h2><p>操作数在内存的固定地址：</p> <div class="highlight"><div class="chroma"> <table class="lntable"><tr><td class="lntd"> <pre tabindex="0" class="chroma"><code><span class="lnt">1 </span></code></pre></td> <td class="lntd"> <pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">MOV AX, [2000h] </span></span></code></pre></td></tr></table> </div> </div><ul> <li>访问 <code>DS:2000h</code> 处的数据</li> <li>地址在编译时确定</li> </ul> <h2 id="寄存器间接寻址"><a href="#%e5%af%84%e5%ad%98%e5%99%a8%e9%97%b4%e6%8e%a5%e5%af%bb%e5%9d%80" class="header-anchor"></a>寄存器间接寻址 </h2><p>地址在寄存器中：</p> <div class="highlight"><div class="chroma"> <table class="lntable"><tr><td class="lntd"> <pre tabindex="0" class="chroma"><code><span class="lnt">1 </span></code></pre></td> <td class="lntd"> <pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">MOV AX, [BX] </span></span></code></pre></td></tr></table> </div> </div><ul> <li>地址 = <code>DS:BX</code></li> <li>适合遍历数组</li> </ul> <h2 id="基址寻址"><a href="#%e5%9f%ba%e5%9d%80%e5%af%bb%e5%9d%80" class="header-anchor"></a>基址寻址 </h2><div class="highlight"><div class="chroma"> <table class="lntable"><tr><td class="lntd"> <pre tabindex="0" class="chroma"><code><span class="lnt">1 </span></code></pre></td> <td class="lntd"> <pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">MOV AX, [BP+10h] </span></span></code></pre></td></tr></table> </div> </div><ul> <li>地址 = <code>SS:BP + 10h</code>（注意用 SS 段）</li> <li>常用于访问局部变量</li> </ul> <h2 id="变址寻址"><a href="#%e5%8f%98%e5%9d%80%e5%af%bb%e5%9d%80" class="header-anchor"></a>变址寻址 </h2><div class="highlight"><div class="chroma"> <table class="lntable"><tr><td class="lntd"> <pre tabindex="0" class="chroma"><code><span class="lnt">1 </span></code></pre></td> <td class="lntd"> <pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">MOV AX, [SI+50h] </span></span></code></pre></td></tr></table> </div> </div><ul> <li>地址 = <code>DS:SI + 50h</code></li> <li>适合数组元素访问</li> </ul> <h2 id="基址变址寻址"><a href="#%e5%9f%ba%e5%9d%80%e5%8f%98%e5%9d%80%e5%af%bb%e5%9d%80" class="header-anchor"></a>基址变址寻址 </h2><div class="highlight"><div class="chroma"> <table class="lntable"><tr><td class="lntd"> <pre tabindex="0" class="chroma"><code><span class="lnt">1 </span></code></pre></td> <td class="lntd"> <pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback"><span class="line"><span class="cl">MOV AX, [BX+SI+100h] </span></span></code></pre></td></tr></table> </div> </div><ul> <li>地址 = <code>DS:BX + SI + 100h</code></li> <li>最灵活，适合二维数组或结构体成员访问</li> </ul> <h2 id="性能对比"><a href="#%e6%80%a7%e8%83%bd%e5%af%b9%e6%af%94" class="header-anchor"></a>性能对比 </h2><table> <thead> <tr> <th style="text-align:left">寻址方式</th> <th style="text-align:center">内存访问次数</th> <th style="text-align:left">相对速度</th> </tr> </thead> <tbody> <tr> <td style="text-align:left">立即数</td> <td style="text-align:center">0</td> <td style="text-align:left">⚡ 最快</td> </tr> <tr> <td style="text-align:left">寄存器</td> <td style="text-align:center">0</td> <td style="text-align:left">⚡ 最快</td> </tr> <tr> <td style="text-align:left">直接</td> <td style="text-align:center">1</td> <td style="text-align:left">较快</td> </tr> <tr> <td style="text-align:left">间接</td> <td style="text-align:center">1</td> <td style="text-align:left">中等</td> </tr> <tr> <td style="text-align:left">基址变址</td> <td style="text-align:center">1</td> <td style="text-align:left">较慢（计算地址）</td> </tr> </tbody> </table> <h2 id="总结"><a href="#%e6%80%bb%e7%bb%93" class="header-anchor"></a>总结 </h2><p>选择合适的寻址方式，是汇编性能优化的第一步。简单变量用直接寻址，数组用变址，结构体用基址变址。</p> <blockquote> <p>下一篇：《堆栈操作深度解析：PUSH/POP 与函数调用的秘密》</p> </blockquote>