Loopy CallSite

[Charles Oliver Nutter]

I played with this some years ago. Doesn't it just become recursive,
because it won't inline through the dynamicInvoker?

- Charlie (mobile)
On Jul 12, 2014 9:36 AM, "Remi Forax" <forax at univ-mlv.fr> wrote:

> It seems that the JIT is lost with whe there is a loopy callsite and never
> stabilize (or the steady state is after the program ends).
>
> import java.lang.invoke.MethodHandle;
> import java.lang.invoke.MethodHandles;
> import java.lang.invoke.MethodType;
> import java.lang.invoke.MutableCallSite;
>
> public class Loop {
>   static class LoopyCS extends MutableCallSite {
>     public LoopyCS() {
>       super(MethodType.methodType(void.class, int.class));
>
>       MethodHandle target = dynamicInvoker();
>       target = MethodHandles.filterArguments(target, 0, FOO);
>       target = MethodHandles.guardWithTest(ZERO,
>           target,
> MethodHandles.dropArguments(MethodHandles.constant(int.class,
> 0).asType(MethodType.methodType(void.class)), 0, int.class));
>       setTarget(target);
>     }
>   }
>
>   static final MethodHandle FOO, ZERO;
>   static {
>     try {
>       FOO = MethodHandles.lookup().findStatic(Loop.class, "foo",
> MethodType.methodType(int.class, int.class));
>       ZERO = MethodHandles.lookup().findStatic(Loop.class, "zero",
> MethodType.methodType(boolean.class, int.class));
>     } catch (NoSuchMethodException | IllegalAccessException e) {
>       throw new AssertionError(e);
>     }
>   }
>
>   private static boolean zero(int i) {
>     return i != 0;
>   }
>
>   private static int foo(int i) {
>     COUNTER++;
>     return i - 1;
>   }
>
>   private static int COUNTER = 0;
>
>   public static void main(String[] args) throws Throwable {
>     for(int i=0; i<100_000; i++) {
>       new LoopyCS().getTarget().invokeExact(1_000);
>     }
>     System.out.println(COUNTER);
>   }
> }
>
> cheers,
> Rémi
>
>
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