anchor.diff:    (lap:mov64 (:object :rbx #.sys.int::+delimited-continuation-prompt+) 0)
     (lap:mov64 (:object :rbx #.sys.int::+delimited-continuation-stack-pointer+) 0)
     (lap:mov64 (:object :rbx #.sys.int::+delimited-continuation-stack+) 0)
  +  ;; Reenable footholds, on the right stack.
  +  (lap:gs)
  +  (lap:sub64 (:object nil #.mezzano.supervisor::+thread-inhibit-footholds+)
  +             #.(ash 1 sys.int::+n-fixnum-bits+))
  +  ;; FIXME: Need to run pending footholds here, but that requires saving the
  +  ;; multiple values. They'll get run eventually, maybe.
     ;; Now return to the function that originally aborted.
     (lap:leave)
     (:gc :no-frame :layout #*0 :multiple-values 0)
     (lap:ret)
     TOO-MANY-VALUES
     (:gc :frame)
  +  PHONY-RETURN-ADDRESS ; match %CALL-WITH-PROMPT's GC info
     (lap:mov64 :r13 (:function error))
     (lap:mov64 :r8 (:constant "Resuming continuation ~S with too many values (MULTPLE-VALUES-LIMIT exceeded)"))
     (lap:mov32 :ecx #.(ash 1 sys.int::+n-fixnum-bits+))
  
positive.code:   (lap:mov64 :r9 (:stack 0)) ; r9 = prompt
    (lap:mov64 :r10 (:stack 1)) ; r10 = values
    ;; r8 = new continuation, r9 = prompt, r10 = values.
    ;; Store the entry point...
    (lap:mov64 :r11 (:function %resume-delimited-continuation))
    (lap:mov64 :rax (:object :r11 #.sys.int::+fref-entry-point+))
  
negative.code:   (lap:lea64 :rax (:rsp #.sys.int::+tag-object+))
    (lap:gs)
    (lap:mov64 (:object nil #.mezzano.supervisor::+thread-special-stack-pointer+) :rax)
    ;; Reenable footholds
    (lap:gs)
    (lap:sub64 (:object nil #.mezzano.supervisor::+thread-inhibit-footholds+)
               #.(ash 1 sys.int::+n-fixnum-bits+))
    (lap:jz RUN-FOOTHOLDS-1)
    CALL-THUNK
    ;; Invoke the thunk.
    (lap:xor32 :ecx :ecx)
    (lap:mov64 :rbx :r9)
    (lap:call (:object :rbx #.sys.int::+function-entry-point+))
    (:gc :frame :layout #*1111 :multiple-values 0)
    ;; Inhibit footholds again.
    (lap:gs)
    (lap:add64 (:object nil #.mezzano.supervisor::+thread-inhibit-footholds+)
               #.(ash 1 sys.int::+n-fixnum-bits+))
    ;; Note: Control will end up back here if the continuation is aborted & resumed.
    ;; Pop continuation.
    (lap:mov64 :rax (:rsp 8))
  