private static LambdaForm preparedLambdaForm(MethodType mtype, int which) {
LambdaForm lform = mtype.form().cachedLambdaForm(which);
if (lform != null) return lform;
lform = makePreparedLambdaForm(mtype, which);
return mtype.form().setCachedLambdaForm(which, lform);
}
