I recently consulted for a very big Common Lisp project having more than one million lines of code (including comments). Let's call it "System X" in the following. System X suffered from extremely long compilation times; i.e., a full recompile took about 33:17 minutes on a 3.1 GHz MacBook Pro Intel Core i7 with SSD and 16 GBs of RAM, using ACL 10.1. It turns out that a number of macros were causing an exponential code blowup. With these macros refactored, the system then recompiled in 5:30 minutes - a speedup by a factor of ~ 6. In this experience report, I will first illuminate the problem, and then demonstrate two potential solutions in terms of macro refactoring techniques. These techniques can be applied in related scenarios.

翻译：笔者近期为某包含百万余行代码（含注释）的大型 Common Lisp 项目提供咨询，下文将其称为"系统 X"。该系统存在编译时间过长的问题：在配备 SSD 及 16GB 内存的 3.1GHz MacBook Pro Intel Core i7 设备上，使用 ACL 10.1 进行完整重编译需耗时约 33 分 17 秒。经排查发现，部分宏定义导致代码量呈指数级膨胀。通过重构这些宏，系统重编译时间缩短至 5 分 30 秒，加速比达约 6 倍。本实践报告将首先阐释问题成因，继而通过宏重构技术展示两种潜在解决方案，这些技术可推广应用于同类场景。