Given a sufficiently bad compiler bug anything is possible, but I think given that it's trying to minimize the size of an input that gives a particular output I don't think it's likely to explore distant branches.
I can't help but wonder about the consteval/constexpr machinery in the various C++ compilers... It'd be interesting to see how much adversarial input has been tested for those.
(I guess Zig's comptime might also be relevant, but I'm not sure what that's allowed to do. Maybe execute arbitrary code?)
... anyway just a stray thought.
If the bug is "the compiler generates an if/else where neither branch is hit", then you would need to execute the code. However, you would likely be able to directly reduce such a bug yourself. When the compiler is generating bad code you can usually just reduce it to that section of code directly. It seems like C-Reduce must be for compiler bugs where it's not generating any code at all (crashing) or the issue isn't with the code generation (extremely slow compiles).
Only if you'te going for compiler bug. If you're working on minimal reproducible example. You need to make sure your code isn't reduced to:
int main() { return 0; }
in that case.
"Enough time" does a lot of work here and warrants further analysis. With enough time it might produce the works of shakespare (if you ignore its designed to minimize), but we should probably view anything that would take more than a year as too much times.