Automatic static and dynamic code analysis for generated code
There may be some issues in compiler-generated code. To find them it may be needed to run a static code analyser like pvs studio against the generated code.

1 the compiler compiles all the library
2 the static code analysis is run against the compiled code.
3 found issues are used to improve the compiler and runtime.

 Fuzzing also may be helpful.
1 the compiler compiles all the formats having test files into C++
2 a program is built
3 a fuzzer is run (I guess there should be a project of a kaitai-powered fuzzer, but it obviously requires serialization)
4 the fuzzing results (crashes) are used to improve compiler and runtime