问题描述
我们正试图实现一个jit编译器，它的性能应该和clang -o4一样。是否有一个地方，我可以很容易地得到clang调用的优化通路列表，指定-o4？
We are trying to implement a jit compiler whose performance is supposed to be same as doing it with clang -o4. Is there a place where I could easily get the list of optimization passes invoked by clang with -o4 is specified?
推荐答案
我知道-O4的意思与-O3 +启用LTO（链接时间优化）相同。
查看下面的代码片段：
As far as I know -O4 means same thing as -O3 + enabled LTO (Link Time Optimization).See the folloing code fragments:
-
//手动将-O转换为-O2，将-O4转换为-O3; -
//检查-O4。
- Tools.cpp
// Manually translate -O to -O2 and -O4 to -O3; - Driver.cpp
// Check for -O4.
a href =http://llvm.org/docs/GoldPlugin.html>此处：
Also see here:
使用-emit-llvm或-flto从clang中获取bitcode文件，有关-O3标志的优化，请参见 PassManagerBuilder.cpp a>文件（查找OptLevel变量 - 它的值为3）。
For optimizations used with -O3 flag see this PassManagerBuilder.cpp file (look for OptLevel variable - it will have value 3).
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