vm_env_cref       552 vm_insnhelper.c     rb_cref_t *cref = vm_env_cref(ep);
vm_env_cref       604 vm_insnhelper.c 	prev_cref = vm_env_cref(blockptr->ep);
vm_env_cref       610 vm_insnhelper.c 	    prev_cref = vm_env_cref(cfp->ep);