关于C#：是否有允许结构重新排序的GCC关键字？

Is there a GCC keyword to allow structure-reordering?

我知道为什么gcc在默认情况下不重新排序结构的成员，但我很少编写依赖于结构顺序的代码，所以有什么方法可以标记结构以便自动重新排序？

以前的GCC版本有-fipa-struct-reorg选项，允许在-fwhole-program和-combine模式下重新排序结构。

-fipa-struct-reorg
Perform structure reorganization optimization, that change C-like structures layout in order to better utilize spatial locality. This transformation is affective for programs containing arrays of structures. Available in two compilation modes: profile-based (enabled with -fprofile-generate) or static (which uses built-in heuristics). Require -fipa-type-escape to provide the safety of this transformation. It works only in whole program mode, so it requires -fwhole-program and -combine to be enabled. Structures considered 'cold' by this transformation are not affected (see --param struct-reorg-cold-struct-ratio=value).

由于发布说明中的以下原因，从GCC 4.8.x中删除了它

The struct reorg and matrix reorg optimizations (command-line options -fipa-struct-reorg and -fipa-matrix-reorg) have been removed. They did not always work correctly, nor did they work with link-time optimization (LTO), hence were only applicable to programs consisting of a single translation unit.

但是，您仍然可以在GCC SVN上尝试struct-reorg-branch，风险由您自己承担，因为它仍在积极开发中。

在GCC中没有这样的选择。而且，我确信，它不能以任何明智的方式引入。关于填充优化，请看下面的讨论。

我知道的唯一例外是热/冷结构字段拆分，在某些情况下可以这样做(但我不确定，GCC甚至可以在配置文件引导模式下这样做，我知道ICC可以)。此功能不受用户控制，并在调用图上执行，在调用图上可以证明数据流上的这种转换是保守的。