mu/mu.arc

;; what happens when our virtual machine starts up
(= initialization-fns* (queue))
(def reset ()
  (each f (as cons initialization-fns*)
    (f)))

(mac on-init body
  `(enq (fn () ,@body)
        initialization-fns*))

(mac init-fn (name . body)
  `(enq (fn ()
;?           (prn ',name)
          (= (function* ',name) (convert-names:convert-labels:convert-braces:insert-code ',body ',name)))
        initialization-fns*))

;; persisting and checking traces for each test
(= traces* (queue))
(= trace-dir* ".traces/")
(ensure-dir trace-dir*)
(= curr-trace-file* nil)
(on-init
  (awhen curr-trace-file*
    (tofile (+ trace-dir* it)
      (each (label trace) (as cons traces*)
        (pr label ": " trace))))
  (= curr-trace-file* nil)
  (= traces* (queue)))

(def new-trace (filename)
;?   (prn "new-trace " filename)
;?   )
  (= curr-trace-file* filename))

(= dump-trace* nil)
(def trace (label . args)
  (when (or (is dump-trace* t)
            (and dump-trace* (is label "-"))
            (and dump-trace* (pos label dump-trace*!whitelist))
            (and dump-trace* (no dump-trace*!whitelist) (~pos label dump-trace*!blacklist)))
    (apply prn label ": " args))
  (enq (list label (apply tostring:prn args))
       traces*))

(redef tr args  ; why am I still returning to prn when debugging? Will this help?
  (do1 nil
       (apply trace "-" args)))

(def tr2 (msg arg)
  (tr msg arg)
  arg)

(def check-trace-contents (msg expected-contents)
  (unless (trace-contents-match expected-contents)
    (prn "F - " msg)
    (prn "  trace contents")
    (print-trace-contents-mismatch expected-contents)))

(def trace-contents-match (expected-contents)
  (each (label msg) (as cons traces*)
    (when (and expected-contents
               (is label expected-contents.0.0)
               (posmatch expected-contents.0.1 msg))
      (pop expected-contents)))
  (no expected-contents))

(def print-trace-contents-mismatch (expected-contents)
  (each (label msg) (as cons traces*)
    (whenlet (expected-label expected-msg)  expected-contents.0
      (if (and (is label expected-label)
               (posmatch expected-msg msg))
        (do (pr "  * ")
            (pop expected-contents))
        (pr "    "))
      (pr label ": " msg)))
  (prn "  couldn't find")
  (each (expected-label expected-msg)  expected-contents
    (prn "  ! " expected-label ": " expected-msg)))

;; virtual machine state

; things that a future assembler will need separate memory for:
;   code; types; args channel
(def clear ()
  (= types* (table))
  (= memory* (table))
  (= function* (table))
  )
(enq clear initialization-fns*)

(on-init
  (= types* (obj
              ; Each type must be scalar or array, sum or product or primitive
              type (obj size 1)  ; implicitly scalar and primitive
              type-address (obj size 1  address t  elem 'type)
              type-array (obj array t  elem 'type)
              type-array-address (obj size 1  address t  elem 'type-array)
              location (obj size 1  address t  elem 'location)  ; assume it points to an atom
              integer (obj size 1)
              boolean (obj size 1)
              boolean-address (obj size 1  address t  elem 'boolean)
              byte (obj size 1)
              byte-address (obj  size 1  address t  elem 'byte)
              string (obj array t  elem 'byte)  ; inspired by Go
              string-address (obj size 1  address t  elem 'string)
              character (obj size 1)  ; int32 like a Go rune
              character-address (obj size 1  address t  elem 'character)
              ; isolating function calls
              scope  (obj array t  elem 'location)  ; by convention index 0 points to outer scope
              scope-address  (obj size 1  address t  elem 'scope)
              ; arrays consist of an integer length followed by the right number of elems
              integer-array (obj array t  elem 'integer)
              integer-array-address (obj size 1  address t  elem 'integer-array)
              integer-array-address-address (obj size 1  address t  elem 'integer-array-address)
              integer-address (obj size 1  address t  elem 'integer)  ; pointer to int
              integer-address-address (obj size 1  address t  elem 'integer-address)
              ; records consist of a series of elems, corresponding to a list of types
              integer-boolean-pair (obj size 2  record t  elems '(integer boolean)  fields '(int bool))
              integer-boolean-pair-address (obj size 1  address t  elem 'integer-boolean-pair)
              integer-boolean-pair-array (obj array t  elem 'integer-boolean-pair)
              integer-boolean-pair-array-address (obj size 1  address t  elem 'integer-boolean-pair-array)
              integer-integer-pair (obj size 2  record t  elems '(integer integer))
              integer-point-pair (obj size 2  record t  elems '(integer integer-integer-pair))
              integer-point-pair-address (obj size 1  address t  elem 'integer-point-pair)
              integer-point-pair-address-address (obj size 1  address t  elem 'integer-point-pair-address)
              ; tagged-values are the foundation of dynamic types
              tagged-value (obj size 2  record t  elems '(type location)  fields '(type payload))
              tagged-value-address (obj size 1  address t  elem 'tagged-value)
              tagged-value-array (obj array t  elem 'tagged-value)
              tagged-value-array-address (obj size 1  address t  elem 'tagged-value-array)
              tagged-value-array-address-address (obj size 1  address t  elem 'tagged-value-array-address)
              ; heterogeneous lists
              list (obj size 2  record t  elems '(tagged-value list-address)  fields '(car cdr))
              list-address (obj size 1  address t  elem 'list)
              list-address-address (obj size 1  address t  elem 'list-address)
              ; parallel routines use channels to synchronize
              channel (obj size 3  record t  elems '(integer integer tagged-value-array-address)  fields '(first-full first-free circular-buffer))
              channel-address (obj size 1  address t  elem 'channel)
              ; editor
              line (obj array t  elem 'character)
              line-address (obj size 1  address t  elem 'line)
              line-address-address (obj size 1  address t  elem 'line-address)
              screen (obj array t  elem 'line-address)
              screen-address (obj size 1  address t  elem 'screen)
              )))

;; managing concurrent routines

; routine = runtime state for a serial thread of execution
(def make-routine (fn-name . args)
  (annotate 'routine (obj call-stack (list
      (obj fn-name fn-name  pc 0  args args  caller-arg-idx 0)))))

(defextend empty (x)  (isa x 'routine)
  (no rep.x!call-stack))

(def stack (routine)
  ((rep routine) 'call-stack))

(mac push-stack (routine op)
  `(push (obj fn-name ,op  pc 0  caller-arg-idx 0)
         ((rep ,routine) 'call-stack)))

(mac pop-stack (routine)
  `(pop ((rep ,routine) 'call-stack)))

(def top (routine)
  stack.routine.0)

(def body (routine (o idx 0))
  (function* stack.routine.idx!fn-name))

(mac pc (routine (o idx 0))  ; assignable
  `((((rep ,routine) 'call-stack) ,idx) 'pc))

(mac caller-arg-idx (routine (o idx 0))  ; assignable
  `((((rep ,routine) 'call-stack) ,idx) 'caller-arg-idx))

(mac caller-args (routine)  ; assignable
  `((((rep ,routine) 'call-stack) 0) 'args))

(mac results (routine)  ; assignable
  `((((rep ,routine) 'call-stack) 0) 'results))

(def waiting-for-exact-cycle? (routine)
  (is 'literal rep.routine!sleep.1))

(def ready-to-wake-up (routine)
  (assert no.routine*)
  (if (is 'literal rep.routine!sleep.1)
    (> curr-cycle* rep.routine!sleep.0)
    (~is rep.routine!sleep.1 (memory* rep.routine!sleep.0))))

(on-init
  (= running-routines* (queue))  ; simple round-robin scheduler
  ; set of sleeping routines; don't modify routines while they're in this table
  (= sleeping-routines* (table))
  (= completed-routines* nil)  ; audit trail
  (= routine* nil)
  (= abort-routine* (parameter nil))
  (= curr-cycle* 0)
  (= scheduling-interval* 500)
  (= scheduler-switch-table* nil)  ; hook into scheduler for tests
  )

; like arc's 'point' but you can also call ((abort-routine*)) in nested calls
(mac routine-mark body
  (w/uniq (g p)
    `(ccc (fn (,g)
            (parameterize abort-routine* (fn ((o ,p)) (,g ,p))
              ,@body)))))

(def run fn-names
  (freeze-functions)
  (= traces* (queue))
  (each it fn-names
    (enq make-routine.it running-routines*))
  (while (~empty running-routines*)
    (= routine* deq.running-routines*)
    (trace "schedule" top.routine*!fn-name)
    (routine-mark
      (run-for-time-slice scheduling-interval*))
    (update-scheduler-state)
;?     (tr "after run iter " running-routines*)
;?     (tr "after run iter " empty.running-routines*)
    ))

; prepare next iteration of round-robin scheduler
;
; state before: routine* running-routines* sleeping-routines*
; state after: running-routines* (with next routine to run at head) sleeping-routines*
;
; responsibilities:
;   add routine* to either running-routines* or sleeping-routines* or completed-routines*
;   wake up any necessary sleeping routines (either by time or on a location)
;   detect deadlock: kill all sleeping routines when none can be woken
(def update-scheduler-state ()
;?   (trace "schedule" curr-cycle*)
  (when routine*
    (if
        rep.routine*!sleep
          (do (trace "schedule" "pushing " top.routine*!fn-name " to sleep queue")
              (set sleeping-routines*.routine*))
        (~empty routine*)
          (do (trace "schedule" "scheduling " top.routine*!fn-name " for further processing")
              (enq routine* running-routines*))
        :else
          (do (trace "schedule" "done with routine")
              (push routine* completed-routines*)))
    (= routine* nil))
  (each (routine _) canon.sleeping-routines*
    (when (ready-to-wake-up routine)
      (trace "schedule" "waking up " top.routine!fn-name)
      (wipe sleeping-routines*.routine)  ; do this before modifying routine
      (wipe rep.routine!sleep)
      (++ pc.routine)
      (enq routine running-routines*)))
  (when (empty running-routines*)
    (whenlet exact-sleeping-routines (keep waiting-for-exact-cycle? keys.sleeping-routines*)
      (let next-wakeup-cycle (apply min (map [rep._!sleep 0] exact-sleeping-routines))
        (= curr-cycle* (+ 1 next-wakeup-cycle))
        (trace "schedule" "skipping to cycle " curr-cycle*)
        (update-scheduler-state))))
  (detect-deadlock))

(def detect-deadlock ()
  (when (and (empty running-routines*)
             (~empty sleeping-routines*)
             (~some 'literal (map (fn(_) rep._!sleep.1)
                                  keys.sleeping-routines*)))
    (each (routine _) sleeping-routines*
      (wipe sleeping-routines*.routine)
      (= rep.routine!error "deadlock detected")
      (push routine completed-routines*))))

(def die (msg)
  (= rep.routine*!error msg)
  (= rep.routine*!stack-trace rep.routine*!call-stack)
  (wipe rep.routine*!call-stack)
  (iflet abort-continuation (abort-routine*)
    (abort-continuation)))

;; running a single routine

; routines consist of instrs
; instrs consist of oargs, op and args
(def parse-instr (instr)
  (iflet delim (pos '<- instr)
    (list (cut instr 0 delim)  ; oargs
          (instr (+ delim 1))  ; op
          (cut instr (+ delim 2)))  ; args
    (list nil instr.0 cdr.instr)))

; operand accessors
(def nondummy (operand)  ; precondition for helpers below
  (~is '_ operand))

(mac v (operand)  ; for value
  `(,operand 0))

(def metadata (operand)
  cdr.operand)

(def ty (operand)
  operand.1)  ; assume type is always first bit of metadata, and it's always present

(def typeinfo (operand)
  (or (types* ty.operand)
      (err "unknown type @(tostring prn.operand)")))

($:require "charterm/main.rkt")

; run instructions from 'routine*' for 'time-slice'
(def run-for-time-slice (time-slice)
  (point return
    (for ninstrs 0 (< ninstrs time-slice) (++ ninstrs)
      (if (empty body.routine*) (err "@stack.routine*.0!fn-name not defined"))
      (while (>= pc.routine* (len body.routine*))
        (pop-stack routine*)
        (if empty.routine* (return ninstrs))
        (++ pc.routine*))
      (++ curr-cycle*)
      (trace "run" "-- " int-canon.memory*)
      (trace "run" curr-cycle* " " top.routine*!fn-name " " pc.routine* ": " (body.routine* pc.routine*))
;?       (trace "run" routine*)
      (when (atom (body.routine* pc.routine*))  ; label
        (when (aand scheduler-switch-table*
                    (alref it (body.routine* pc.routine*)))
          (++ pc.routine*)
          (trace "run" "context-switch forced " abort-routine*)
          ((abort-routine*)))
        (++ pc.routine*)
        (continue))
      (let (oarg op arg)  (parse-instr (body.routine* pc.routine*))
        (let results
              (case op
                ; arithmetic
                add
                  (do (trace "add" (m arg.0) " " (m arg.1))
                  (+ (m arg.0) (m arg.1))
                  )
                sub
                  (- (m arg.0) (m arg.1))
                mul
                  (* (m arg.0) (m arg.1))
                div
                  (/ (real (m arg.0)) (m arg.1))
                idiv
                  (list (trunc:/ (m arg.0) (m arg.1))
                        (mod (m arg.0) (m arg.1)))

                ; boolean
                and
                  (and (m arg.0) (m arg.1))
                or
                  (or (m arg.0) (m arg.1))
                not
                  (not (m arg.0))

                ; comparison
                eq
                  (is (m arg.0) (m arg.1))
                neq
                  (do (trace "neq" (m arg.0) " " (m arg.1))
                  (~is (m arg.0) (m arg.1))
                  )
                lt
                  (< (m arg.0) (m arg.1))
                gt
                  (> (m arg.0) (m arg.1))
                le
                  (<= (m arg.0) (m arg.1))
                ge
                  (>= (m arg.0) (m arg.1))

                ; control flow
                jump
                  (do (= pc.routine* (+ 1 pc.routine* (v arg.0)))
                      (trace "jump" "jumping to " pc.routine*)
                      (continue))
                jump-if
                  (let flag (m arg.0)
                    (trace "jump" "checking that " flag " is t")
                    (when (is t flag)
                      (= pc.routine* (+ 1 pc.routine* (v arg.1)))
                      (trace "jump" "jumping to " pc.routine*)
                      (continue)))
                jump-unless  ; convenient helper
                  (let flag (m arg.0)
                    (trace "jump" "checking that " flag " is not t")
                    (unless (is t flag)
                      (= pc.routine* (+ 1 pc.routine* (v arg.1)))
                      (trace "jump" "jumping to " pc.routine*)
                      (continue)))

                ; data management: scalars, arrays, records
                copy
                  (m arg.0)
                get
                  (with (operand  (canonize arg.0)
                         idx  (v arg.1))
                    (assert (is 'offset (ty arg.1)) "record index @arg.1 must have type 'offset'")
                    (assert (< -1 idx (len typeinfo.operand!elems)) "@idx is out of bounds of record @operand")
                    (m (list (apply + v.operand
                                      (map sizeof (firstn idx typeinfo.operand!elems)))
                             typeinfo.operand!elems.idx
                             'global)))
                get-address
                  (with (operand  (canonize arg.0)
                         idx  (v arg.1))
                    (assert (is 'offset (ty arg.1)) "record index @arg.1 must have type 'offset'")
                    (assert (< -1 idx (len typeinfo.operand!elems)) "@idx is out of bounds of record @operand")
                    (apply + v.operand
                             (map sizeof (firstn idx typeinfo.operand!elems))))
                index
                  (withs (operand  (canonize arg.0)
                          elemtype  typeinfo.operand!elem
                          idx  (m arg.1))
                    (unless (< -1 idx array-len.operand)
                      (die "@idx is out of bounds of array @operand"))
                    (m (list (+ v.operand
                                1  ; for array size
                                (* idx sizeof.elemtype))
                             elemtype
                             'global)))
                index-address
                  (withs (operand  (canonize arg.0)
                          elemtype  typeinfo.operand!elem
                          idx  (m arg.1))
                    (unless (< -1 idx array-len.operand)
                      (die "@idx is out of bounds of array @operand"))
                    (+ v.operand
                       1  ; for array size
                       (* idx sizeof.elemtype)))
                new
                  (if (isa arg.0 'string)
                    ; special-case: allocate space for a literal string
                    (new-string arg.0)
                    (let type (v arg.0)
                      (assert (is 'literal (ty arg.0)) "new: second arg @arg.0 must be literal")
                      (if (no types*.type)  (err "no such type @type"))
                      ; todo: initialize memory. currently racket does it for us
                      (if types*.type!array
                        (new-array type (m arg.1))
                        (new-scalar type))))
                sizeof
                  (sizeof (m arg.0))
                len
                  (let base arg.0
                    (if (or typeinfo.base!array typeinfo.base!address)
                      array-len.base
                      -1))

                ; tagged-values require one primitive
                save-type
                  (annotate 'record `(,(ty arg.0) ,(m arg.0)))

                ; multiprocessing
                run
                  (run (v arg.0))
                fork
                  (enq (apply make-routine (v car.arg) (map m cdr.arg)) running-routines*)
                ; todo: errors should stall a process and let its parent
                ; inspect it
                assert
                  (assert (m arg.0))
                sleep
                  (let operand arg.0
                    ; store sleep as either (<cycle number> literal) or (<location> <current value>)
                    (if (is ty.operand 'literal)
                      (let delay v.operand
                        (trace "run" "sleeping until " (+ curr-cycle* delay))
                        (= rep.routine*!sleep `(,(+ curr-cycle* delay) literal)))
                      (do
;?                         (tr "blocking on " operand " -> " (addr operand))
                        (= rep.routine*!sleep `(,addr.operand ,m.operand))))
                    ((abort-routine*)))

                ; text interaction
                cls
                  (do1 nil ($.charterm-clear-screen))
                cll
                  (do1 nil ($.charterm-clear-line))
                cursor
                  (do1 nil ($.charterm-cursor (m arg.0) (m arg.1)))
                print-primitive
                  (do1 nil ((if ($.current-charterm) $.charterm-display pr) (m arg.0)))
                getc
                  (and ($.charterm-byte-ready?) ($.charterm-read-key))
                bold-mode
                  (do1 nil ($.charterm-bold))
                non-bold-mode
                  (do1 nil ($.charterm-normal))
                console-on
                  (do1 nil (if (no ($.current-charterm)) ($.open-charterm)))
                console-off
                  (do1 nil (if ($.current-charterm) ($.close-charterm)))

                ; user-defined functions
                arg
                  (do (when arg
                        (assert (is 'literal (ty arg.0)))
                        (= caller-arg-idx.routine* (v arg.0)))
                      (let idx caller-arg-idx.routine*
                        (++ caller-arg-idx.routine*)
                        (trace "arg" arg " " idx " " caller-args.routine*)
                        (if (len> caller-args.routine* idx)
                          (list caller-args.routine*.idx t)
                          (list nil nil))))
                prepare-reply
                  (prepare-reply arg)
                reply
                  (do (when arg
                        (prepare-reply arg))
                      (let results results.routine*
                        (pop-stack routine*)
                        (if empty.routine* (return ninstrs))
                        (let (caller-oargs _ _)  (parse-instr (body.routine* pc.routine*))
                          (trace "reply" arg " " caller-oargs)
                          (each (dest val)  (zip caller-oargs results)
                            (when nondummy.dest
                              (trace "reply" val " => " dest)
                              (setm dest val))))
                        (++ pc.routine*)
                        (while (>= pc.routine* (len body.routine*))
                          (pop-stack routine*)
                          (when empty.routine* (return ninstrs))
                          (++ pc.routine*))
                        (continue)))
                ; else try to call as a user-defined function
                  (do (if function*.op
                        (let callee-args (accum yield
                                           (each a arg
                                             (yield (m a))))
                          (push-stack routine* op)
                          (= caller-args.routine* callee-args))
                        (err "no such op @op"))
                      (continue))
                )
              ; opcode generated some 'results'
              ; copy to output args
              (if (acons results)
                (each (dest val) (zip oarg results)
                  (unless (is dest '_)
                    (trace "run" val " => " dest)
                    (setm dest val)))
                (when oarg  ; must be a list
                  (trace "run" results " => " oarg.0)
                  (setm oarg.0 results)))
              )
        (++ pc.routine*)))
    (return time-slice)))

(def prepare-reply (args)
  (= results.routine*
     (accum yield
       (each a args
         (yield (m a))))))

; helpers for memory access respecting
;   immediate addressing - 'literal' and 'offset'
;   direct addressing - default
;   indirect addressing - 'deref'
;   relative addressing - if routine* has 'default-scope'

(def m (loc)  ; read memory, respecting metadata
  (point return
    (if (in ty.loc 'literal 'offset)
      (return v.loc))
    (when (is v.loc 'default-scope)
      (return rep.routine*!call-stack.0!default-scope))
    (trace "m" loc)
    (assert (isa v.loc 'int) "addresses must be numeric (problem in convert-names?) @loc")
    (with (n  sizeof.loc
           addr  addr.loc)
;?       (trace "m" "reading " n " locations starting at " addr)
      (if (is 1 n)
            memory*.addr
          :else
            (annotate 'record
                      (map memory* (addrs addr n)))))))

(def setm (loc val)  ; set memory, respecting metadata
  (point return
    (when (is v.loc 'default-scope)
      (assert (is 1 sizeof.loc) "can't store compounds in default-scope @loc")
      (= rep.routine*!call-stack.0!default-scope val)
      (return))
    (assert (isa v.loc 'int) "can't store to non-numeric address (problem in convert-names?)")
    (trace "setm" loc " <= " val)
    (with (n  (if (isa val 'record) (len rep.val) 1)
           addr  addr.loc)
      (trace "setm" "size of " loc " is " n)
      (assert n "setm: can't compute type of @loc")
      (assert addr "setm: null pointer @loc")
      (if (is 1 n)
        (do (assert (~isa val 'record) "setm: record of size 1 @(tostring prn.val)")
            (trace "setm" loc ": setting " addr " to " val)
            (= memory*.addr val))
        (do (if ((types* typeof.loc) 'array)
              ; size check for arrays
              (when (~is n
                         (+ 1  ; array length
                            (* rep.val.0 (sizeof ((types* typeof.loc) 'elem)))))
                (die "writing invalid array @(tostring prn.val)"))
              ; size check for non-arrays
              (when (~is sizeof.loc n)
                (die "writing to incorrect size @(tostring prn.val) => @loc")))
            (let addrs (addrs addr n)
              (each (dest src) (zip addrs rep.val)
                (trace "setm" loc ": setting " dest " to " src)
                (= memory*.dest src))))))))

(def typeof (operand)
  (let loc absolutize.operand
    (while (pos 'deref metadata.loc)
      (zap deref loc))
    ty.loc))

(def addr (operand)
  (let loc absolutize.operand
    (while (pos 'deref metadata.loc)
      (zap deref loc))
    v.loc))

(def addrs (n sz)
  (accum yield
    (repeat sz
      (yield n)
      (++ n))))

(def canonize (operand)
  (ret operand
    (zap absolutize operand)
    (while (pos 'deref metadata.operand)
      (zap deref operand))))

(def array-len (operand)
  (trace "array-len" operand)
  (zap absolutize operand)
  (while (pos 'deref metadata.operand)
    (zap deref operand))
  (if typeinfo.operand!array
        (m `(,v.operand integer ,@(cut operand 2)))
      :else
        (err "can't take len of non-array @operand")))

(def sizeof (x)
  (trace "sizeof" x)
  (point return
  (when (acons x)
;?     (tr "aa " x)
    (zap absolutize x)
;?     (tr "bb " x)
    (while (pos 'deref metadata.x)
;?       (tr "cc " x)
      (zap deref x))
;?     (tr "dd " x)
;?     (trace "sizeof" "after canonizing: " x)
    (when typeinfo.x!array
      (return (+ 1 (* (m `(,v.x integer ,@(cut x 2)))
                      (sizeof typeinfo.x!elem))))))
  (let type (if (and acons.x (pos 'deref metadata.x))
                  typeinfo.x!elem  ; deref pointer
                acons.x
                  ty.x
                :else  ; naked type
                  x)
    (assert types*.type "sizeof: no such type @type")
    (if (~or types*.type!record types*.type!array)
          types*.type!size
        types*.type!record
          (sum idfn
            (accum yield
              (each elem types*.type!elems
                (yield sizeof.elem))))
        :else
          (err "sizeof can't handle @type (arrays require a specific variable)")))))

(def absolutize (operand)
  (if (no routine*)
        operand
      (pos 'global metadata.operand)
        operand
      :else
        (iflet base rep.routine*!call-stack.0!default-scope
          (if (< v.operand memory*.base)
            `(,(+ v.operand base) ,@metadata.operand global)
            (die "no room for var @operand in routine of size @memory*.base"))
          operand)))

(def deref (operand)
  (assert (pos 'deref metadata.operand))
  (assert typeinfo.operand!address)
  (apply list (memory* v.operand)
              typeinfo.operand!elem
              (drop-one 'deref (cut operand 2))))

(def drop-one (f x)
  (when acons.x  ; proper lists only
    (if (testify.f car.x)
      cdr.x
      (cons car.x (drop-one f x)))))

; memory allocation

(enq (fn () (= Memory-in-use-until 1000))
     initialization-fns*)

(def new-scalar (type)
  (ret result Memory-in-use-until
    (++ Memory-in-use-until sizeof.type)))

(def new-array (type size)
;?   (prn "new array: @type @size")
  (ret result Memory-in-use-until
    (++ Memory-in-use-until (+ 1 (* (sizeof types*.type!elem) size)))
    (= memory*.result size)))

(def new-string (literal-string)
  (ret result Memory-in-use-until
    (= memory*.Memory-in-use-until len.literal-string)
    (++ Memory-in-use-until)
    (each c literal-string
      (= memory*.Memory-in-use-until c)
      (++ Memory-in-use-until))))

;; desugar structured assembly based on blocks

(def convert-braces (instrs)
  (let locs ()  ; list of information on each brace: (open/close pc)
    (let pc 0
      (loop (instrs instrs)
        (each instr instrs
          (if (or atom.instr (~is 'begin instr.0))  ; label or regular instruction
                (do
                  (trace "c{0" pc " " instr " -- " locs)
                  (++ pc))
                ; hack: racket replaces braces with parens, so we need the
                ; keyword 'begin' to delimit blocks.
                ; ultimately there'll be no nesting and braces will just be
                ; in an instr by themselves.
              :else  ; brace
                (do
                  (push `(open ,pc) locs)
                  (recur cdr.instr)
                  (push `(close ,pc) locs))))))
    (zap rev locs)
    (with (pc  0
           stack  ())  ; elems are pcs
      (accum yield
        (loop (instrs instrs)
          (each instr instrs
            (point continue
            (when (atom instr)  ; label
              (yield instr)
              (++ pc)
              (continue))
            (let delim (or (pos '<- instr) -1)
              (with (oarg  (if (>= delim 0)
                             (cut instr 0 delim))
                     op  (instr (+ delim 1))
                     arg  (cut instr (+ delim 2)))
                (trace "c{1" pc " " op " " oarg)
                (case op
                  begin
                    (do
                      (push pc stack)
                      (assert (is oarg nil) "begin: can't take oarg in @instr")
                      (recur arg)
                      (pop stack)
                      (continue))
                  break
                    (do
                      (assert (is oarg nil) "break: can't take oarg in @instr")
                      (yield `(jump (,(close-offset pc locs (and arg arg.0.0)) offset))))
                  break-if
                    (do
                      (assert (is oarg nil) "break-if: can't take oarg in @instr")
                      (yield `(jump-if ,arg.0 (,(close-offset pc locs (and cdr.arg arg.1.0)) offset))))
                  break-unless
                    (do
                      (assert (is oarg nil) "break-unless: can't take oarg in @instr")
                      (yield `(jump-unless ,arg.0 (,(close-offset pc locs (and cdr.arg arg.1.0)) offset))))
                  loop
                    (do
                      (assert (is oarg nil) "loop: can't take oarg in @instr")
                      (yield `(jump (,(open-offset pc stack (and arg arg.0.0)) offset))))
                  loop-if
                    (do
                      (trace "cvt0" "loop-if: " instr " => " (- stack.0 1))
                      (assert (is oarg nil) "loop-if: can't take oarg in @instr")
                      (yield `(jump-if ,arg.0 (,(open-offset pc stack (and cdr.arg arg.1.0)) offset))))
                  loop-unless
                    (do
                      (trace "cvt0" "loop-if: " instr " => " (- stack.0 1))
                      (assert (is oarg nil) "loop-unless: can't take oarg in @instr")
                      (yield `(jump-unless ,arg.0 (,(open-offset pc stack (and cdr.arg arg.1.0)) offset))))
                  ;else
                    (yield instr))))
            (++ pc))))))))

(def close-offset (pc locs nblocks)
  (or= nblocks 1)
;?   (tr nblocks)
  (point return
;?   (tr "close " pc " " locs)
  (let stacksize 0
    (each (state loc) locs
      (point continue
;?       (tr stacksize "/" done " " state " " loc)
      (when (<= loc pc)
        (continue))
;?       (tr "process " stacksize loc)
      (if (is 'open state) (++ stacksize) (-- stacksize))
      ; last time
;?       (tr "process2 " stacksize loc)
      (when (is stacksize (* -1 nblocks))
;?         (tr "close now " loc)
        (return (- loc pc 1))))))))

(def open-offset (pc stack nblocks)
  (or= nblocks 1)
  (- (stack (- nblocks 1)) 1 pc))

;; convert jump targets to offsets

(def convert-labels (instrs)
;?   (tr "convert-labels " instrs)
  (let labels (table)
    (let pc 0
      (each instr instrs
        (when (~acons instr)
;?           (tr "label " pc)
          (= labels.instr pc))
        (++ pc)))
    (let pc 0
      (each instr instrs
        (when (and acons.instr
                   (in car.instr 'jump 'jump-if 'jump-unless))
          (each arg cdr.instr
;?             (tr "trying " arg " " ty.arg ": " v.arg " => " (labels v.arg))
            (when (and (is ty.arg 'offset)
                       (isa v.arg 'sym)
                       (labels v.arg))
              (= v.arg (- (labels v.arg) pc 1)))))
        (++ pc))))
  instrs)

;; convert symbolic names to raw memory locations

(def convert-names (instrs)
  (with (location  (table)
         isa-field  (table))
    (let idx 1
      (each instr instrs
        (point continue
        (when atom.instr
          (continue))
        (trace "cn0" instr " " canon.location " " canon.isa-field)
        (let (oargs op args)  (parse-instr instr)
          (if (in op 'get 'get-address)
            (with (basetype  (typeinfo args.0)
                   field  (v args.1))
              (assert basetype "no such type @args.0")
              (trace "cn0" "field-access " field)
              ; todo: need to rename args.0 as well?
              (when (pos 'deref (metadata args.0))
                (trace "cn0" "field-access deref")
                (assert basetype!address "@args.0 requests deref, but it's not an address of a record")
                (= basetype (types* basetype!elem)))
              (when (isa field 'sym)
                (assert (or (~location field) isa-field.field) "field @args.1 is also a variable")
                (when (~location field)
                  (trace "cn0" "new field; computing location")
                  (assert basetype!fields "no field names available for @instr")
                  (iflet idx (pos field basetype!fields)
                    (do (set isa-field.field)
                        (trace "cn0" "field location @idx")
                        (= location.field idx))
                    (assert nil "couldn't find field in @instr")))))
            (each arg args
              (assert (~isa-field v.arg) "arg @arg is also a field name")
              (when (maybe-add arg location idx)
                (err "use before set: @arg"))))
          (each arg oargs
            (trace "cn0" "checking " arg)
            (unless (is arg '_)
              (assert (~isa-field v.arg) "oarg @arg is also a field name")
              (when (maybe-add arg location idx)
                (trace "cn0" "location for arg " arg ": " idx)
                ; todo: can't allocate arrays on the stack
                (++ idx (sizeof ty.arg)))))))))
    (trace "cn1" "update names " canon.location " " canon.isa-field)
    (each instr instrs
      (when (acons instr)
        (let (oargs op args)  (parse-instr instr)
          (each arg args
            (when (and nondummy.arg (location v.arg))
              (zap location v.arg)))
          (each arg oargs
            (when (and nondummy.arg (location v.arg))
              (zap location v.arg))))))
    instrs))

(def maybe-add (arg location idx)
  (trace "maybe-add" arg)
  (when (and nondummy.arg
             (~in ty.arg 'literal 'offset 'fn)
             (~location v.arg)
             (isa v.arg 'sym)
             (~in v.arg 'nil 'default-scope)
             (~pos 'global metadata.arg))
    (= (location v.arg) idx)))

;; literate tangling system for reordering code

(def convert-quotes (instrs)
  (let deferred (queue)
    (each instr instrs
      (when (acons instr)
        (case instr.0
          defer
            (let (q qinstrs)  instr.1
              (assert (is 'make-br-fn q) "defer: first arg must be [quoted]")
              (each qinstr qinstrs
                (enq qinstr deferred))))))
    (accum yield
      (each instr instrs
        (unless (and acons.instr
                     (in instr.0 'defer))  ; keep sync'd with case clauses above
          (yield instr)))
      (each instr (as cons deferred)
        (yield instr)))))

(on-init
  (= before* (table))  ; label -> queue of fragments
  (= after* (table)))  ; label -> list of fragments

; see add-code below for adding to before* and after*

(def insert-code (instrs (o name))
  (loop (instrs instrs)
    (accum yield
      (each instr instrs
        (if (and (acons instr) (~is 'begin car.instr))
              ; simple instruction
              (yield instr)
            (and (acons instr) (is 'begin car.instr))
              ; block
              (yield `{begin ,@(recur cdr.instr)})
            (atom instr)
              ; label
              (do
;?                 (prn "tangling " instr)
                (each fragment (as cons (or (and name (before* (sym:string name '/ instr)))
                                            before*.instr))
                  (each instr fragment
                    (yield instr)))
                (yield instr)
                (each fragment (or (and name (after* (sym:string name '/ instr)))
                                   after*.instr)
                  (each instr fragment
                    (yield instr)))))))))

;; system software

(init-fn maybe-coerce
  ((default-scope scope-address) <- new (scope literal) (30 literal))
  ((x tagged-value-address) <- new (tagged-value literal))
  ((x tagged-value-address deref) <- arg)
  ((p type) <- arg)
  ((xtype type) <- get (x tagged-value-address deref) (0 offset))
  ((match? boolean) <- eq (xtype type) (p type))
  { begin
    (break-if (match? boolean))
    (reply (0 literal) (nil literal))
  }
  ((xvalue location) <- get (x tagged-value-address deref) (1 offset))
  (reply (xvalue location) (match? boolean)))

(init-fn new-tagged-value
  ((default-scope scope-address) <- new (scope literal) (30 literal))
  ; assert (sizeof arg.0) == 1
  ((xtype type) <- arg)
  ((xtypesize integer) <- sizeof (xtype type))
  ((xcheck boolean) <- eq (xtypesize integer) (1 literal))
  (assert (xcheck boolean))
  ; todo: check that arg 0 matches the type? or is that for the future typechecker?
  ((result tagged-value-address) <- new (tagged-value literal))
  ; result->type = arg 0
  ((resulttype location) <- get-address (result tagged-value-address deref) (type offset))
  ((resulttype location deref) <- copy (xtype type))
  ; result->payload = arg 1
  ((locaddr location) <- get-address (result tagged-value-address deref) (payload offset))
  ((locaddr location deref) <- arg)
  (reply (result tagged-value-address)))

(init-fn list-next  ; list-address -> list-address
  ((default-scope scope-address) <- new (scope literal) (30 literal))
  ((base list-address) <- arg)
  ((result list-address) <- get (base list-address deref) (cdr offset))
  (reply (result list-address)))

(init-fn list-value-address  ; list-address -> tagged-value-address
  ((default-scope scope-address) <- new (scope literal) (30 literal))
  ((base list-address) <- arg)
  ((result tagged-value-address) <- get-address (base list-address deref) (car offset))
  (reply (result tagged-value-address)))

(init-fn new-list
  ((default-scope scope-address) <- new (scope literal) (30 literal))
  ; new-list = curr = new list
  ((new-list-result list-address) <- new (list literal))
  ((curr list-address) <- copy (new-list-result list-address))
  { begin
    ; while read curr-value
    ((curr-value integer) (exists? boolean) <- arg)
    (break-unless (exists? boolean))
    ; curr.cdr = new list
    ((next list-address-address) <- get-address (curr list-address deref) (cdr offset))
    ((next list-address-address deref) <- new (list literal))
    ; curr = curr.cdr
    ((curr list-address) <- list-next (curr list-address))
    ; curr.car = (type curr-value)
    ((dest tagged-value-address) <- list-value-address (curr list-address))
    ((dest tagged-value-address deref) <- save-type (curr-value integer))
    (loop)
  }
  ; return new-list.cdr
  ((new-list-result list-address) <- list-next (new-list-result list-address))  ; memory leak
  (reply (new-list-result list-address)))

(init-fn new-channel
  ((default-scope scope-address) <- new (scope literal) (30 literal))
  ; result = new channel
  ((result channel-address) <- new (channel literal))
  ; result.first-full = 0
  ((full integer-address) <- get-address (result channel-address deref) (first-full offset))
  ((full integer-address deref) <- copy (0 literal))
  ; result.first-free = 0
  ((free integer-address) <- get-address (result channel-address deref) (first-free offset))
  ((free integer-address deref) <- copy (0 literal))
  ; result.circular-buffer = new tagged-value[arg+1]
  ((capacity integer) <- arg)
  ((capacity integer) <- add (capacity integer) (1 literal))  ; unused slot for full? below
  ((channel-buffer-address tagged-value-array-address-address) <- get-address (result channel-address deref) (circular-buffer offset))
  ((channel-buffer-address tagged-value-array-address-address deref) <- new (tagged-value-array literal) (capacity integer))
  (reply (result channel-address)))

(init-fn capacity
  ((default-scope scope-address) <- new (scope literal) (30 literal))
  ((chan channel) <- arg)
  ((q tagged-value-array-address) <- get (chan channel) (circular-buffer offset))
  ((qlen integer) <- len (q tagged-value-array-address deref))
  (reply (qlen integer)))

(init-fn write
  ((default-scope scope-address) <- new (scope literal) (30 literal))
  ((chan channel-address) <- arg)
  ((val tagged-value) <- arg)
  { begin
    ; block if chan is full
    ((full boolean) <- full? (chan channel-address deref))
    (break-unless (full boolean))
    ((full-address integer-address) <- get-address (chan channel-address deref) (first-full offset))
    (sleep (full-address integer-address deref))
  }
  ; store val
  ((q tagged-value-array-address) <- get (chan channel-address deref) (circular-buffer offset))
  ((free integer-address) <- get-address (chan channel-address deref) (first-free offset))
  ((dest tagged-value-address) <- index-address (q tagged-value-array-address deref) (free integer-address deref))
  ((dest tagged-value-address deref) <- copy (val tagged-value))
  ; increment free
  ((free integer-address deref) <- add (free integer-address deref) (1 literal))
  { begin
    ; wrap free around to 0 if necessary
    ((qlen integer) <- len (q tagged-value-array-address deref))
    ((remaining? boolean) <- lt (free integer-address deref) (qlen integer))
    (break-if (remaining? boolean))
    ((free integer-address deref) <- copy (0 literal))
  }
  (reply (chan channel-address deref)))

(init-fn read
  ((default-scope scope-address) <- new (scope literal) (30 literal))
  ((chan channel-address) <- arg)
  { begin
    ; block if chan is empty
    ((empty boolean) <- empty? (chan channel-address deref))
    (break-unless (empty boolean))
    ((free-address integer-address) <- get-address (chan channel-address deref) (first-free offset))
    (sleep (free-address integer-address deref))
  }
  ; read result
  ((full integer-address) <- get-address (chan channel-address deref) (first-full offset))
  ((q tagged-value-array-address) <- get (chan channel-address deref) (circular-buffer offset))
  ((result tagged-value) <- index (q tagged-value-array-address deref) (full integer-address deref))
  ; increment full
  ((full integer-address deref) <- add (full integer-address deref) (1 literal))
  { begin
    ; wrap full around to 0 if necessary
    ((qlen integer) <- len (q tagged-value-array-address deref))
    ((remaining? boolean) <- lt (full integer-address deref) (qlen integer))
    (break-if (remaining? boolean))
    ((full integer-address deref) <- copy (0 literal))
  }
  (reply (result tagged-value) (chan channel-address deref)))

; An empty channel has first-empty and first-full both at the same value.
(init-fn empty?
  ((default-scope scope-address) <- new (scope literal) (30 literal))
  ; return arg.first-full == arg.first-free
  ((chan channel) <- arg)
  ((full integer) <- get (chan channel) (first-full offset))
  ((free integer) <- get (chan channel) (first-free offset))
  ((result boolean) <- eq (full integer) (free integer))
  (reply (result boolean)))

; A full channel has first-empty just before first-full, wasting one slot.
; (Other alternatives: https://en.wikipedia.org/wiki/Circular_buffer#Full_.2F_Empty_Buffer_Distinction)
(init-fn full?
  ((default-scope scope-address) <- new (scope literal) (30 literal))
  ((chan channel) <- arg)
  ; curr = chan.first-free + 1
  ((curr integer) <- get (chan channel) (first-free offset))
  ((curr integer) <- add (curr integer) (1 literal))
  { begin
    ; if (curr == chan.capacity) curr = 0
    ((qlen integer) <- capacity (chan channel))
    ((remaining? boolean) <- lt (curr integer) (qlen integer))
    (break-if (remaining? boolean))
    ((curr integer) <- copy (0 literal))
  }
  ; return chan.first-full == curr
  ((full integer) <- get (chan channel) (first-full offset))
  ((result boolean) <- eq (full integer) (curr integer))
  (reply (result boolean)))

(init-fn strcat
  ((default-scope scope-address) <- new (scope literal) (30 literal))
  ; result = new string[a.length + b.length]
  ((a string-address) <- arg)
  ((a-len integer) <- len (a string-address deref))
  ((b string-address) <- arg)
  ((b-len integer) <- len (b string-address deref))
  ((result-len integer) <- add (a-len integer) (b-len integer))
  ((result string-address) <- new (string literal) (result-len integer))
  ; result-idx = i = 0
  ((result-idx integer) <- copy (0 literal))
  ; copy a into result
  ((i integer) <- copy (0 literal))
  { begin
    ; while (i < a.length)
    ((a-done? boolean) <- lt (i integer) (a-len integer))
    (break-unless (a-done? boolean))
    ; result[result-idx] = a[i]
    ((out byte-address) <- index-address (result string-address deref) (result-idx integer))
    ((in byte) <- index (a string-address deref) (i integer))
    ((out byte-address deref) <- copy (in byte))
    ; ++i
    ((i integer) <- add (i integer) (1 literal))
    ; ++result-idx
    ((result-idx integer) <- add (result-idx integer) (1 literal))
    (loop)
  }
  ; copy b into result
  ((i integer) <- copy (0 literal))
  { begin
    ; while (i < b.length)
    ((b-done? boolean) <- lt (i integer) (b-len integer))
    (break-unless (b-done? boolean))
    ; result[result-idx] = a[i]
    ((out byte-address) <- index-address (result string-address deref) (result-idx integer))
    ((in byte) <- index (b string-address deref) (i integer))
    ((out byte-address deref) <- copy (in byte))
    ; ++i
    ((i integer) <- add (i integer) (1 literal))
    ; ++result-idx
    ((result-idx integer) <- add (result-idx integer) (1 literal))
    (loop)
  }
  (reply (result string-address)))

; replace underscores in first with remaining args
(init-fn interpolate  ; string-address template, string-address a
  ((default-scope scope-address) <- new (scope literal) (30 literal))
  ; result-len = template.length + a.length - 1 (we'll the '_')
  ((template string-address) <- arg)
  ((tem-len integer) <- len (template string-address deref))
  ((a string-address) <- arg)
  ((a-len integer) <- len (a string-address deref))
  ((result-len integer) <- add (tem-len integer) (a-len integer))
  ((result-len integer) <- sub (result-len integer) (1 literal))
  ; result = new string[result-len]
  ((result string-address) <- new (string literal) (result-len integer))
  ; result-idx = i = 0
  ((result-idx integer) <- copy (0 literal))
  ((i integer) <- copy (0 literal))
  { begin
    ; copy template into result until '_'
    { begin
      ; while (i < template.length)
      ((tem-done? boolean) <- lt (i integer) (tem-len integer))
      (break-unless (tem-done? boolean) (2 blocks))
      ; while template[i] != '_'
      ((in byte) <- index (template string-address deref) (i integer))
      ((underscore? boolean) <- eq (in byte) (#\_ literal))
      (break-if (underscore? boolean))
      ; result[result-idx] = template[i]
      ((out byte-address) <- index-address (result string-address deref) (result-idx integer))
      ((out byte-address deref) <- copy (in byte))
      ; ++i
      ((i integer) <- add (i integer) (1 literal))
      ; ++result-idx
      ((result-idx integer) <- add (result-idx integer) (1 literal))
      (loop)
    }
;?     (print-primitive ("i now: " literal))
;?     (print-primitive (i integer))
;?     (print-primitive ("\n" literal))
    ; copy 'a' into result
    ((j integer) <- copy (0 literal))
    { begin
      ; while (j < a.length)
      ((arg-done? boolean) <- lt (j integer) (a-len integer))
      (break-unless (arg-done? boolean))
      ; result[result-idx] = a[j]
      ((in byte) <- index (a string-address deref) (j integer))
      ((out byte-address) <- index-address (result string-address deref) (result-idx integer))
      ((out byte-address deref) <- copy (in byte))
      ; ++j
      ((j integer) <- add (j integer) (1 literal))
      ; ++result-idx
      ((result-idx integer) <- add (result-idx integer) (1 literal))
      (loop)
    }
    ; skip '_' in template
    ((i integer) <- add (i integer) (1 literal))
    ; copy rest of template into result
    { begin
      ; while (i < template.length)
      ((tem-done? boolean) <- lt (i integer) (tem-len integer))
      (break-unless (tem-done? boolean))
      ; result[result-idx] = template[i]
      ((in byte) <- index (template string-address deref) (i integer))
      ((out byte-address) <- index-address (result string-address deref) (result-idx integer))
      ((out byte-address deref) <- copy (in byte))
      ; ++i
      ((i integer) <- add (i integer) (1 literal))
      ; ++result-idx
      ((result-idx integer) <- add (result-idx integer) (1 literal))
      (loop)
    }
  }
  (reply (result string-address)))

(def canon (table)
  (sort (compare < [tostring (prn:car _)]) (as cons table)))

(def int-canon (table)
  (sort (compare < car) (as cons table)))

;; loading code into the virtual machine

(def add-code (forms)
  (each (op . rest)  forms
    (case op
      ; syntax: def <name> [ <instructions> ]
      ; don't apply our lightweight tools just yet
      def!
        (let (name (_make-br-fn body))  rest
          (assert (is 'make-br-fn _make-br-fn))
          (= function*.name body))
      def
        (let (name (_make-br-fn body))  rest
          (assert (is 'make-br-fn _make-br-fn))
          (= function*.name (join body function*.name)))

      ; syntax: before <label> [ <instructions> ]
      ;
      ; multiple before directives => code in order
      before
        (let (label (_make-br-fn fragment))  rest
          (assert (is 'make-br-fn _make-br-fn))
          (or= before*.label (queue))
          (enq fragment before*.label))

      ; syntax: after <label> [ <instructions> ]
      ;
      ; multiple after directives => code in *reverse* order
      ; (if initialization order in a function is A B, corresponding
      ; finalization order should be B A)
      after
        (let (label (_make-br-fn fragment))  rest
          (assert (is 'make-br-fn _make-br-fn))
          (push fragment after*.label))
      )))

(def freeze-functions ()
  (each (name body)  canon.function*
;?     (tr name)
;?     (prn keys.before* " -- " keys.after*)
;?     (= function*.name (convert-names:convert-labels:convert-braces:prn:insert-code body)))
    (= function*.name (convert-names:convert-labels:convert-braces:insert-code body name))))

;; load all provided files and start at 'main'
(reset)
(awhen cdr.argv
  (map add-code:readfile it)
;?   (= dump-trace* (obj whitelist '("run" "schedule" "add")))
;?   (freeze-functions)
;?   (prn function*!factorial)
  (run 'main)
  (if ($.current-charterm) ($.close-charterm))
  (prn memory*)
;?   (prn completed-routines*)
)