Is the jit supposed to hoist init type checks this hard?

[crystal-rgb]

Consider static types A with a method void OhGodWhy and B with another method void DoWork and a static constructor (.cctor) .

static class A
{
    static bool IsInit;
    static int LoopCount;

    public static void OhGodWhy()
    {
        if (!IsInit)
            return;

        for (int i = 0; i < LoopCount; i++)
            B.DoWork();
    }
}

static class B
{
    static B()
    {
        // observable side effect
    }

    public static void DoWork() {  /* Actual code */ }
}

(Note that this isn't a minimal repro as I couldn't isolate the behaviour.)
In Release, depending on the shape of the code, the generated asm for OhGodWhy will have the first instruction a type initialisation check for type B followed by a conditional jump to said initialisation and a jump back to the first written line of code. This makes the type B .cctor always run even if we never touch B, by returning early.

Is this intended behaviour? And if so then what's causing it? 👀

I would love to learn more about how the JIT reasons, thank you for your time! 🙂

[huoyaoyuan]

In practice, a type is often considered touched when a method referencing the type get touched.

The timing of static constructor is non-deterministic. It's not suggested to depend on its side effect.