;;;; machine-independent disassembler

;;;; This software is part of the SBCL system. See the README file for
;;;; more information.
;;;;
;;;; This software is derived from the CMU CL system, which was
;;;; written at Carnegie Mellon University and released into the
;;;; public domain. The software is in the public domain and is
;;;; provided with absolutely no warranty. See the COPYING and CREDITS
;;;; files for more information.

(in-package "SB!DISASSEM")

;;; types and defaults

(def!constant label-column-width 7)

(deftype text-width () '(integer 0 1000))
(deftype alignment () '(integer 0 64))
(deftype offset () '(signed-byte 24))
(deftype address () '(unsigned-byte #.sb!vm:n-word-bits))
(deftype disassem-length () '(unsigned-byte 24))
(deftype column () '(integer 0 1000))

(def!constant max-filtered-value-index 32)
(deftype filtered-value-index ()
  `(integer 0 (,max-filtered-value-index)))
(deftype filtered-value-vector ()
  `(simple-array t (,max-filtered-value-index)))

;;;; disassembly parameters

;;; instructions
(defvar *disassem-insts* (make-hash-table :test 'eq))
(declaim (type hash-table *disassem-insts*))

(defvar *disassem-inst-space* nil)

;;; minimum alignment of instructions, in bytes
(defvar *disassem-inst-alignment-bytes* sb!vm:n-word-bytes)
(declaim (type alignment *disassem-inst-alignment-bytes*))

;; How many columns of output to allow for the address preceding each line.
;; If NIL, use the minimum possible width for the disassembly range.
;; If 0, do not print addresses.
(defvar *disassem-location-column-width* nil)
(declaim (type (or null text-width) *disassem-location-column-width*))

;;; the width of the column in which instruction-names are printed. A
;;; value of zero gives the effect of not aligning the arguments at
;;; all.
(defvar *disassem-opcode-column-width* 0)
(declaim (type text-width *disassem-opcode-column-width*))

;;; the width of the column in which instruction-bytes are printed. A
;;; value of zero disables the printing of instruction bytes.
(defvar *disassem-inst-column-width* 16
  #!+sb-doc
  "The width of instruction bytes.")
(declaim (type text-width *disassem-inst-column-width*))

(defvar *disassem-note-column* (+ 45 *disassem-inst-column-width*)
  #!+sb-doc
  "The column in which end-of-line comments for notes are started.")

;;;; cached functions
;;;;
;;;; There's no need for 1000 different versions of a function equivalent
;;;; to (PROGN (PRINT ADDR) (PRINT OPCODE) (PRINT ARG)) so we try to
;;;; coalesce sexprs, since there is no such thing as coalescing compiled code.
;;;; This is not really a "cache" as much as hashtable for coalescing.

(defstruct (fun-cache (:copier nil)
                      (:print-object (lambda (self stream)
                                       (print-unreadable-object
                                         (self stream :type t :identity t)))))
  (serial-number 0 :type fixnum)
  (printers nil :type list)
  (labellers nil :type list)
  (prefilters nil :type list))

(defvar *disassem-fun-cache* (make-fun-cache))
(declaim (type fun-cache *disassem-fun-cache*))

;;;; A DCHUNK contains the bits we look at to decode an
;;;; instruction.
;;;; I tried to keep this abstract so that if using integers > the machine
;;;; word size conses too much, it can be changed to use bit-vectors or
;;;; something.
;;;;
;;;; KLUDGE: It's not clear that using bit-vectors would be any more efficient.
;;;; Perhaps the abstraction could go away. -- WHN 19991124

#!-sb-fluid
(declaim (inline dchunk-or dchunk-and dchunk-clear dchunk-not
                 dchunk-make-mask dchunk-make-field
                 sap-ref-dchunk
                 dchunk-extract
                 dchunk=
                 dchunk-count-bits))

(def!constant dchunk-bits #.sb!vm:n-word-bits)

(deftype dchunk ()
  `(unsigned-byte ,dchunk-bits))
(deftype dchunk-index ()
  `(integer 0 ,dchunk-bits))

(def!constant dchunk-zero 0)
(def!constant dchunk-one #.(1- (expt 2 sb!vm:n-word-bits)))

(defun dchunk-extract (from pos)
  (declare (type dchunk from))
  (the dchunk (ldb pos (the dchunk from))))

(defmacro dchunk-copy (x)
  `(the dchunk ,x))

(defun dchunk-or (to from)
  (declare (type dchunk to from))
  (the dchunk (logior to from)))
(defun dchunk-and (to from)
  (declare (type dchunk to from))
  (the dchunk (logand to from)))
(defun dchunk-clear (to from)
  (declare (type dchunk to from))
  (the dchunk (logandc2 to from)))
(defun dchunk-not (from)
  (declare (type dchunk from))
  (the dchunk (logand dchunk-one (lognot from))))

(defmacro dchunk-andf (to from)
  `(setf ,to (dchunk-and ,to ,from)))
(defmacro dchunk-orf (to from)
  `(setf ,to (dchunk-or ,to ,from)))
(defmacro dchunk-clearf (to from)
  `(setf ,to (dchunk-clear ,to ,from)))

(defun dchunk-make-mask (pos)
  (the dchunk (mask-field pos -1)))
(defun dchunk-make-field (pos value)
  (the dchunk (dpb value pos 0)))

(defmacro make-dchunk (value)
  `(the dchunk ,value))

#-sb-xc-host ;; FIXME: function belongs in 'target-disassem'
(defun sap-ref-dchunk (sap byte-offset byte-order)
  (declare (type sb!sys:system-area-pointer sap)
           (type offset byte-offset)
           (muffle-conditions compiler-note) ; returns possible bignum
           (optimize (speed 3) (safety 0)))
  (the dchunk
       (ecase dchunk-bits
         (32 (if (eq byte-order :big-endian)
                 (+ (ash (sb!sys:sap-ref-8 sap byte-offset) 24)
                    (ash (sb!sys:sap-ref-8 sap (+ 1 byte-offset)) 16)
                    (ash (sb!sys:sap-ref-8 sap (+ 2 byte-offset)) 8)
                    (sb!sys:sap-ref-8 sap (+ 3 byte-offset)))
                 (+ (sb!sys:sap-ref-8 sap byte-offset)
                    (ash (sb!sys:sap-ref-8 sap (+ 1 byte-offset)) 8)
                    (ash (sb!sys:sap-ref-8 sap (+ 2 byte-offset)) 16)
                    (ash (sb!sys:sap-ref-8 sap (+ 3 byte-offset)) 24))))
         (64 (if (eq byte-order :big-endian)
                 (+ (ash (sb!sys:sap-ref-8 sap byte-offset) 56)
                    (ash (sb!sys:sap-ref-8 sap (+ 1 byte-offset)) 48)
                    (ash (sb!sys:sap-ref-8 sap (+ 2 byte-offset)) 40)
                    (ash (sb!sys:sap-ref-8 sap (+ 3 byte-offset)) 32)
                    (ash (sb!sys:sap-ref-8 sap (+ 4 byte-offset)) 24)
                    (ash (sb!sys:sap-ref-8 sap (+ 5 byte-offset)) 16)
                    (ash (sb!sys:sap-ref-8 sap (+ 6 byte-offset)) 8)
                    (sb!sys:sap-ref-8 sap (+ 7 byte-offset)))
                 (+ (sb!sys:sap-ref-8 sap byte-offset)
                    (ash (sb!sys:sap-ref-8 sap (+ 1 byte-offset)) 8)
                    (ash (sb!sys:sap-ref-8 sap (+ 2 byte-offset)) 16)
                    (ash (sb!sys:sap-ref-8 sap (+ 3 byte-offset)) 24)
                    (ash (sb!sys:sap-ref-8 sap (+ 4 byte-offset)) 32)
                    (ash (sb!sys:sap-ref-8 sap (+ 5 byte-offset)) 40)
                    (ash (sb!sys:sap-ref-8 sap (+ 6 byte-offset)) 48)
                    (ash (sb!sys:sap-ref-8 sap (+ 7 byte-offset)) 56)))))))

(defun dchunk-corrected-extract (from pos unit-bits byte-order)
  (declare (type dchunk from))
  (if (eq byte-order :big-endian)
      (ldb (byte (byte-size pos)
                 (+ (byte-position pos) (- dchunk-bits unit-bits)))
           (the dchunk from))
      (ldb pos (the dchunk from))))

(defmacro dchunk-insertf (place pos value)
  `(setf ,place (the dchunk (dpb ,value ,pos (the dchunk,place)))))

(defun dchunk= (x y)
  (declare (type dchunk x y))
  (= x y))
(defmacro dchunk-zerop (x)
  `(dchunk= ,x dchunk-zero))

(defun dchunk-strict-superset-p (sup sub)
  (and (zerop (logandc2 sub sup))
       (not (zerop (logandc2 sup sub)))))

(defun dchunk-count-bits (x)
  (declare (type dchunk x))
  (logcount x))

(defstruct (instruction (:conc-name inst-)
                        (:constructor
                         make-instruction (name
                                           format-name
                                           print-name
                                           length
                                           mask id
                                           printer
                                           labeller prefilter control))
                        (:copier nil))
  (name nil :type (or symbol string))
  (format-name nil :type (or symbol string))

  (mask dchunk-zero :type dchunk)       ; bits in the inst that are constant
  (id dchunk-zero :type dchunk)         ; value of those constant bits

  (length 0 :type disassem-length)               ; in bytes

  (print-name nil :type symbol)

  ;; disassembly functions
  (prefilter nil :type (or null function))
  (labeller nil :type (or null function))
  (printer (missing-arg) :type (or null function))
  (control nil :type (or null function))

  ;; instructions that are the same as this instruction but with more
  ;; constraints
  (specializers nil :type list))
(def!method print-object ((inst instruction) stream)
  (print-unreadable-object (inst stream :type t :identity t)
    (format stream "~A(~A)" (inst-name inst) (inst-format-name inst))))

;;;; an instruction space holds all known machine instructions in a
;;;; form that can be easily searched

(defstruct (inst-space (:conc-name ispace-)
                       (:copier nil))
  (valid-mask dchunk-zero :type dchunk) ; applies to *children*
  (choices nil :type list))
(def!method print-object ((ispace inst-space) stream)
  (print-unreadable-object (ispace stream :type t :identity t)))

;;; now that we've defined the structure, we can declaim the type of
;;; the variable:
(declaim (type (or null inst-space) *disassem-inst-space*))

(defstruct (inst-space-choice (:conc-name ischoice-)
                              (:copier nil))
  (common-id dchunk-zero :type dchunk)  ; applies to *parent's* mask
  (subspace (missing-arg) :type (or inst-space instruction)))

;;;; These are the kind of values we can compute for an argument, and
;;;; how to compute them. The :CHECKER functions make sure that a given
;;;; argument is compatible with another argument for a given use.

(defvar *arg-form-kinds* nil)

(defstruct (arg-form-kind (:copier nil))
  (names nil :type list)
  (producer (missing-arg) :type function)
  (checker (missing-arg) :type function))

(defun arg-form-kind-or-lose (kind)
  (or (getf *arg-form-kinds* kind)
      (pd-error "unknown arg-form kind ~S" kind)))

(defun find-arg-form-producer (kind)
  (arg-form-kind-producer (arg-form-kind-or-lose kind)))
(defun find-arg-form-checker (kind)
  (arg-form-kind-checker (arg-form-kind-or-lose kind)))

(defun canonicalize-arg-form-kind (kind)
  (car (arg-form-kind-names (arg-form-kind-or-lose kind))))

;;;; only used during compilation of the instructions for a backend
;;;;
;;;; FIXME: If only used then, isn't there some way we could do
;;;; EVAL-WHEN tricks to keep this stuff from appearing in the target
;;;; system?

(defvar *disassem-inst-formats* (make-hash-table))
(defvar *disassem-arg-types* nil)
(defvar *disassem-fun-cache* (make-fun-cache))

(defstruct (arg (:copier nil)
                (:predicate nil)
                (:constructor %make-arg (name &optional position))
                (:constructor standard-make-arg) ; only so #S readmacro works
                (:print-object
                 (lambda (self stream)
                   (if *print-readably*
                       (call-next-method)
                       (print-unreadable-object (self stream :type t)
                         (format stream
                                 "~D:~A ~:[~;+~]~:S~@[=~S~]~@[ filt=~S~]~
~@[ lbl=~S~]~@[ prt=~S~]"
                                 (arg-position self)
                                 (arg-name self)
                                 (arg-sign-extend-p self)
                                 (arg-fields self)
                                 (arg-value self)
                                 (arg-prefilter self)
                                 (arg-use-label self)
                                 (arg-printer self)))))))
  (name nil :type symbol)
  (fields nil :type list)

  (value nil :type (or list integer))
  (sign-extend-p nil :type (member t nil))

  ;; position in a vector of prefiltered values
  (position 0 :type fixnum)

  ;; functions to use
  (printer nil)
  (prefilter nil)
  (use-label nil))

(defstruct (instruction-format (:conc-name format-)
                               (:constructor make-inst-format
                                             (name length default-printer args))
                               (:copier nil))
  (name nil)
  (args nil :type list)

  (length 0 :type disassem-length)               ; in bytes

  (default-printer nil :type list))

;;; A FUNSTATE holds the state of any arguments used in a disassembly
;;; function.
(defstruct (funstate (:conc-name funstate-)
                     (:constructor %make-funstate)
                     (:copier nil))
  (args nil :type list)
  (arg-temps nil :type list))           ; See below.

(defun make-funstate (args)
  ;; give the args a position
  (let ((i 0))
    (dolist (arg args)
      (setf (arg-position arg) i)
      (incf i)))
  (%make-funstate :args args))

(defun funstate-compatible-p (funstate args)
  (every (lambda (this-arg-temps)
           (let* ((old-arg (car this-arg-temps))
                  (new-arg (find (arg-name old-arg) args :key #'arg-name)))
             (and new-arg
                  (= (arg-position old-arg) (arg-position new-arg))
                  (every (lambda (this-kind-temps)
                           (funcall (find-arg-form-checker
                                     (car this-kind-temps))
                                    new-arg
                                    old-arg))
                         (cdr this-arg-temps)))))
         (funstate-arg-temps funstate)))

(defun arg-or-lose (name funstate)
  (let ((arg (find name (funstate-args funstate) :key #'arg-name)))
    (when (null arg)
      (pd-error "unknown argument ~S" name))
    arg))

;;;; Since we can't include some values in compiled output as they are
;;;; (notably functions), we sometimes use a VALSRC structure to keep
;;;; track of the source from which they were derived.

(defstruct (valsrc (:constructor %make-valsrc)
                   (:copier nil))
  (value nil)
  (source nil))

(defun make-valsrc (value source)
  (cond ((equal value source)
         source)
        ((and (listp value) (eq (car value) 'function))
         value)
        (t
         (%make-valsrc :value value :source source))))

;;; machinery to provide more meaningful error messages during compilation
(defvar *current-instruction-flavor* nil)
(defun pd-error (fmt &rest args)
  (if *current-instruction-flavor*
      (error "~@<in printer-definition for ~S(~S): ~3I~:_~?~:>"
             (car *current-instruction-flavor*)
             (cdr *current-instruction-flavor*)
             fmt args)
      (apply #'error fmt args)))

;;; FIXME:
;;;  1. This should become a utility in SB!INT.
;;;  2. Arrays and structures and maybe other things are
;;;     self-evaluating too.
(defun self-evaluating-p (x)
  (typecase x
    (null t)
    (keyword t)
    (symbol (eq x t))
    (cons nil)
    (t t)))

(defun maybe-quote (evalp form)
  (if (or evalp (self-evaluating-p form)) form `',form))

;;; Detect things that obviously don't need wrapping, like
;;; variable-refs and #'function.
(defun doesnt-need-wrapping-p (form)
  (or (symbolp form)
      (and (listp form)
           (eq (car form) 'function)
           (symbolp (cadr form)))))

(defun make-wrapper (form arg-name funargs prefix)
  (if (and (listp form)
           (eq (car form) 'function))
      ;; a function def
      (let ((wrapper-name (symbolicate prefix "-" arg-name "-WRAPPER"))
            (wrapper-args (make-gensym-list (length funargs))))
        (values `#',wrapper-name
                `(defun ,wrapper-name ,wrapper-args
                   (funcall ,form ,@wrapper-args))))
      ;; something else
      (let ((wrapper-name (symbolicate "*" prefix "-" arg-name "-WRAPPER*")))
        (values wrapper-name `(defparameter ,wrapper-name ,form)))))

(defun filter-overrides (overrides evalp)
  (mapcar (lambda (override)
            (list* (car override) (cadr override)
                   (munge-fun-refs (cddr override) evalp)))
          overrides))

(defparameter *arg-fun-params*
  '((:printer . (value stream dstate))
    (:use-label . (value dstate))
    (:prefilter . (value dstate))))

(defun munge-fun-refs (params evalp &optional wrap-defs-p (prefix ""))
  (let ((params (copy-list params)))
    (do ((tail params (cdr tail))
         (wrapper-defs nil))
        ((null tail)
         (values params (nreverse wrapper-defs)))
      (let ((fun-arg (assoc (car tail) *arg-fun-params*)))
        (when fun-arg
          (let* ((fun-form (cadr tail))
                 (quoted-fun-form `',fun-form))
            (when (and wrap-defs-p (not (doesnt-need-wrapping-p fun-form)))
              (multiple-value-bind (access-form wrapper-def-form)
                  (make-wrapper fun-form (car fun-arg) (cdr fun-arg) prefix)
                (setf quoted-fun-form `',access-form)
                (push wrapper-def-form wrapper-defs)))
            (if evalp
                (setf (cadr tail)
                      `(make-valsrc ,fun-form ,quoted-fun-form))
                (setf (cadr tail)
                      fun-form))))))))

(defun gen-args-def-form (overrides format-form &optional (evalp t))
  (let ((args-var (gensym)))
    `(let ((,args-var (copy-list (format-args ,format-form))))
       ,@(mapcar (lambda (override)
                   (update-args-form args-var
                                     `',(car override)
                                     (and (cdr override)
                                          (cons :value (cdr override)))
                                     evalp))
                 overrides)
       ,args-var)))

(defun gen-printer-def-forms-def-form (base-name
                                       def
                                       &optional
                                       (evalp t))
  (declare (type symbol base-name))
  (destructuring-bind
      (format-name
       (&rest field-defs)
       &optional (printer-form :default)
       &key ((:print-name print-name-form) `',base-name) control)
      def
    (let ((format-var (gensym))
          (field-defs (filter-overrides field-defs evalp)))
      `(let* ((*current-instruction-flavor* ',(cons base-name format-name))
              (,format-var (format-or-lose ',format-name))
              (args ,(gen-args-def-form field-defs format-var evalp))
              (funcache *disassem-fun-cache*))
         (multiple-value-bind (printer-fun printer-defun)
             (find-printer-fun ,(if (eq printer-form :default)
                                     `(format-default-printer ,format-var)
                                     (maybe-quote evalp printer-form))
                               args funcache)
           (multiple-value-bind (labeller-fun labeller-defun)
               (find-labeller-fun args funcache)
             (multiple-value-bind (prefilter-fun prefilter-defun)
                 (find-prefilter-fun args funcache)
               (multiple-value-bind (mask id)
                   (compute-mask-id args)
                 (values
                  `(make-instruction ',',base-name
                                     ',',format-name
                                     ,',print-name-form
                                     ,(format-length ,format-var)
                                     ,mask
                                     ,id
                                     ,(and printer-fun `#',printer-fun)
                                     ,(and labeller-fun `#',labeller-fun)
                                     ,(and prefilter-fun `#',prefilter-fun)
                                     ,',control)
                  `(progn
                     ,@(and printer-defun (list printer-defun))
                     ,@(and labeller-defun (list labeller-defun))
                     ,@(and prefilter-defun (list prefilter-defun))))
                 ))))))))

(defun update-args-form (var name-form descrip-forms evalp)
  `(setf ,var
         ,(if evalp
              `(modify-or-add-arg ,name-form ,var ,@descrip-forms)
              `(apply #'modify-or-add-arg ,name-form ,var ',descrip-forms))))

(defun format-or-lose (name)
  (or (gethash name *disassem-inst-formats*)
      (pd-error "unknown instruction format ~S" name)))

;;; FIXME: needed only at build-the-system time, not in running system
;;; and FIXME: better syntax would allow inheriting the length to avoid
;;; re-stating it needlessly in some derived formats. Perhaps:
;;; (DEFINE-INSTRUCTION-FORMAT NAME (:bits N [more-format-keys]*) &rest fields)
;;;
(defmacro define-instruction-format ((format-name length-in-bits
                                      &key default-printer include)
                                     &rest arg-specs)
  #!+sb-doc
  "DEFINE-INSTRUCTION-FORMAT (Name Length {Format-Key Value}*) Arg-Def*
  Define an instruction format NAME for the disassembler's use. LENGTH is
  the length of the format in bits.
  Possible FORMAT-KEYs:

  :INCLUDE other-format-name
      Inherit all arguments and properties of the given format. Any
      arguments defined in the current format definition will either modify
      the copy of an existing argument (keeping in the same order with
      respect to when prefilters are called), if it has the same name as
      one, or be added to the end.
  :DEFAULT-PRINTER printer-list
      Use the given PRINTER-LIST as a format to print any instructions of
      this format when they don't specify something else.

  Each ARG-DEF defines one argument in the format, and is of the form
    (Arg-Name {Arg-Key Value}*)

  Possible ARG-KEYs (the values are evaluated unless otherwise specified):

  :FIELDS byte-spec-list
      The argument takes values from these fields in the instruction. If
      the list is of length one, then the corresponding value is supplied by
      itself; otherwise it is a list of the values. The list may be NIL.
  :FIELD byte-spec
      The same as :FIELDS (list byte-spec).

  :VALUE value
      If the argument only has one field, this is the value it should have,
      otherwise it's a list of the values of the individual fields. This can
      be overridden in an instruction-definition or a format definition
      including this one by specifying another, or NIL to indicate that it's
      variable.

  :SIGN-EXTEND boolean
      If non-NIL, the raw value of this argument is sign-extended,
      immediately after being extracted from the instruction (before any
      prefilters are run, for instance). If the argument has multiple
      fields, they are all sign-extended.

  :TYPE arg-type-name
      Inherit any properties of the given argument type.

  :PREFILTER function
      A function which is called (along with all other prefilters, in the
      order that their arguments appear in the instruction-format) before
      any printing is done, to filter the raw value. Any uses of READ-SUFFIX
      must be done inside a prefilter.

  :PRINTER function-string-or-vector
      A function, string, or vector which is used to print this argument.

  :USE-LABEL
      If non-NIL, the value of this argument is used as an address, and if
      that address occurs inside the disassembled code, it is replaced by a
      label. If this is a function, it is called to filter the value."
  (let ((length-var (gensym)) ; are lengths ever non-constant? probably not.
        (inherited-args
         (if include
             (copy-list (format-args (format-or-lose include)))))
        added-args readers all-wrapper-defs)
    (dolist (arg-spec arg-specs)
      (let ((arg-name (car arg-spec)))
        (multiple-value-bind (props wrapper-defs)
            (munge-fun-refs (cdr arg-spec) t t
                            (symbolicate format-name '- arg-name))
          (setf all-wrapper-defs (nconc wrapper-defs all-wrapper-defs))
          (let ((reader (getf props :reader)))
            (when reader
              (setq readers (list* #!-sb-fluid `(declaim (inline ,reader))
                                   `(defun ,reader (dchunk dstate)
                                      (declare (ignorable dchunk dstate))
                                      (arg-access-macro ,arg-name ,format-name
                                                        dchunk dstate))
                                   readers))
              (remf props :reader))) ; ok because MUNGEing copied the plist
          (let ((cell (member arg-name inherited-args
                              :key (lambda (x)
                                     (arg-name (if (listp x) (second x) x))))))
            (cond ((not cell)
                   (push `(make-arg
                           ,(+ (length inherited-args) (length added-args))
                           ,length-var ',arg-name ,@props)
                         added-args))
                  (props ; do nothing if no alterations
                   (rplaca cell
                           `(copy-arg ,(car cell) ,length-var ,@props))))))))
    `(progn
       ,@all-wrapper-defs
       (eval-when (:compile-toplevel :execute)
         (let ((,length-var ,length-in-bits))
           (setf (gethash ',format-name *disassem-inst-formats*)
                 (make-inst-format ',format-name (bits-to-bytes ,length-var)
                                   ,(maybe-quote t default-printer)
                                   (list ,@inherited-args
                                         ,@(nreverse added-args))))))
       ,@readers)))

(defun make-arg (number format-length-bits name &rest properties)
  (apply #'modify-arg (%make-arg name number) format-length-bits properties))

(defun copy-arg (arg format-length-bits &rest properties)
  (apply #'modify-arg (copy-structure arg) format-length-bits properties))

;;; FIXME: probably needed only at build-the-system time, not in
;;; final target system
(defun modify-or-add-arg (arg-name args &rest properties)
  (declare (dynamic-extent properties))
  (when (get-properties properties '(:field :fields))
    (error "~@<in arg ~S: ~3I~:_~
          can't specify fields except using DEFINE-INSTRUCTION-FORMAT~:>"
           arg-name))
  (let* ((cell (member arg-name args :key #'arg-name))
         (arg (if cell
                  (setf (car cell) (copy-structure (car cell)))
                  (let ((arg (%make-arg arg-name)))
                    (setf args (nconc args (list arg)))
                    arg))))
    (apply #'modify-arg arg nil properties)
    args))

(defun modify-arg (arg format-length
                   &key   (value nil value-p)
                          (type nil type-p)
                          (prefilter nil prefilter-p)
                          (printer nil printer-p)
                          (sign-extend nil sign-extend-p)
                          (use-label nil use-label-p)
                          (field nil field-p)
                          (fields nil fields-p))
  (when field-p
    (if fields-p
        (error ":FIELD and :FIELDS are mutually exclusive")
        (setf fields (list field) fields-p t)))
  (when type-p
    (set-arg-from-type arg type *disassem-arg-types*))
  (when value-p
    (setf (arg-value arg) value))
  (when prefilter-p
    (setf (arg-prefilter arg) prefilter))
  (when sign-extend-p
    (setf (arg-sign-extend-p arg) sign-extend))
  (when printer-p
    (setf (arg-printer arg) printer))
  (when use-label-p
    (setf (arg-use-label arg) use-label))
  (when fields-p
    (setf (arg-fields arg)
          (mapcar (lambda (bytespec)
                    (when (> (+ (byte-position bytespec) (byte-size bytespec))
                             format-length)
                      (error "~@<in arg ~S: ~3I~:_~
                                   The field ~S doesn't fit in an ~
                                   instruction-format ~W bits wide.~:>"
                             (arg-name arg) bytespec format-length))
                    (correct-dchunk-bytespec-for-endianness
                     bytespec format-length sb!c:*backend-byte-order*))
                  fields)))
  arg)

;; Generate a sexpr to extract ARG-NAME of FORMAT-NAME using CHUNK and DSTATE.
;; The first two arguments to this macro are not runtime-evaluated.
(defmacro arg-access-macro (arg-name format-name chunk dstate)
  (let* ((funstate (make-funstate (format-args (format-or-lose format-name))))
         (arg (arg-or-lose arg-name funstate))
         (arg-val-form (arg-value-form arg funstate :adjusted)))
    `(flet ((local-filtered-value (offset)
              (declare (type filtered-value-index offset))
              (aref (dstate-filtered-values ,dstate) offset))
            (local-extract (bytespec)
              (dchunk-extract ,chunk bytespec)))
       (declare (ignorable #'local-filtered-value #'local-extract)
                (inline local-filtered-value local-extract))
       (let* ,(make-arg-temp-bindings funstate) ,arg-val-form))))

(defun arg-value-form (arg funstate
                       &optional
                       (kind :final)
                       (allow-multiple-p (not (eq kind :numeric))))
  (let ((forms (gen-arg-forms arg kind funstate)))
    (when (and (not allow-multiple-p)
               (listp forms)
               (/= (length forms) 1))
      (pd-error "~S must not have multiple values." arg))
    (maybe-listify forms)))

(defun correct-dchunk-bytespec-for-endianness (bs unit-bits byte-order)
  (if (eq byte-order :big-endian)
      (byte (byte-size bs) (+ (byte-position bs) (- dchunk-bits unit-bits)))
      bs))

(defun make-arg-temp-bindings (funstate)
  ;; (Everything is in reverse order, so we just use PUSH, which
  ;; results in everything being in the right order at the end.)
  (let ((bindings nil))
    (dolist (ats (funstate-arg-temps funstate))
      (dolist (atk (cdr ats))
        (cond ((null (cadr atk)))
              ((atom (cadr atk))
               (push `(,(cadr atk) ,(cddr atk)) bindings))
              (t
               (mapc (lambda (var form)
                       (push `(,var ,form) bindings))
                     (cadr atk)
                     (cddr atk))))))
    bindings))

(defun gen-arg-forms (arg kind funstate)
  (multiple-value-bind (vars forms)
      (get-arg-temp arg kind funstate)
    (when (null forms)
      (multiple-value-bind (new-forms single-value-p)
          (funcall (find-arg-form-producer kind) arg funstate)
        (setq forms new-forms)
        (cond ((or single-value-p (atom forms))
               (unless (symbolp forms)
                 (setq vars (gensym))))
              ((every #'symbolp forms)
               ;; just use the same as the forms
               (setq vars nil))
              (t
               (setq vars (make-gensym-list (length forms)))))
        (set-arg-temps vars forms arg kind funstate)))
    (or vars forms)))

(defun maybe-listify (forms)
  (cond ((atom forms)
         forms)
        ((/= (length forms) 1)
         `(list ,@forms))
        (t
         (car forms))))

(defun set-arg-from-type (arg type-name table)
  (let ((type-arg (find type-name table :key #'arg-name)))
    (when (null type-arg)
      (pd-error "unknown argument type: ~S" type-name))
    (setf (arg-printer arg) (arg-printer type-arg))
    (setf (arg-prefilter arg) (arg-prefilter type-arg))
    (setf (arg-sign-extend-p arg) (arg-sign-extend-p type-arg))
    (setf (arg-use-label arg) (arg-use-label type-arg))))

(defun get-arg-temp (arg kind funstate)
  (let ((this-arg-temps (assoc arg (funstate-arg-temps funstate))))
    (if this-arg-temps
        (let ((this-kind-temps
               (assoc (canonicalize-arg-form-kind kind)
                      (cdr this-arg-temps))))
          (values (cadr this-kind-temps) (cddr this-kind-temps)))
        (values nil nil))))

(defun set-arg-temps (vars forms arg kind funstate)
  (let ((this-arg-temps
         (or (assoc arg (funstate-arg-temps funstate))
             (car (push (cons arg nil) (funstate-arg-temps funstate)))))
        (kind (canonicalize-arg-form-kind kind)))
    (let ((this-kind-temps
           (or (assoc kind (cdr this-arg-temps))
               (car (push (cons kind nil) (cdr this-arg-temps))))))
      (setf (cdr this-kind-temps) (cons vars forms)))))

;;; DEFINE-ARG-TYPE Name {Key Value}*
;;;
;;; Define a disassembler argument type NAME (which can then be referenced in
;;; another argument definition using the :TYPE argument). &KEY args are:
;;;
;;;  :SIGN-EXTEND boolean
;;;     If non-NIL, the raw value of this argument is sign-extended.
;;;
;;;  :TYPE arg-type-name
;;;     Inherit any properties of given arg-type.
;;;
;;; :PREFILTER function
;;;     A function which is called (along with all other prefilters,
;;;     in the order that their arguments appear in the instruction-
;;;     format) before any printing is done, to filter the raw value.
;;;     Any uses of READ-SUFFIX must be done inside a prefilter.
;;;
;;; :PRINTER function-string-or-vector
;;;     A function, string, or vector which is used to print an argument of
;;;     this type.
;;;
;;; :USE-LABEL
;;;     If non-NIL, the value of an argument of this type is used as
;;;     an address, and if that address occurs inside the disassembled
;;;     code, it is replaced by a label. If this is a function, it is
;;;     called to filter the value.
(defmacro define-arg-type (name &rest args
                           &key sign-extend type prefilter printer use-label)
  (declare (ignore sign-extend type prefilter printer use-label))
  (multiple-value-bind (args wrapper-defs)
      (munge-fun-refs args t t name)
    `(progn
       ,@wrapper-defs
       (eval-when (:compile-toplevel :execute)
         (setq *disassem-arg-types*
               (delete ',name *disassem-arg-types* :key #'arg-name))
         (push (modify-arg (%make-arg ',name) nil ,@args) *disassem-arg-types*))
       ',name)))

(defmacro def-arg-form-kind ((&rest names) &rest inits)
  `(let ((kind (make-arg-form-kind :names ',names ,@inits)))
     ,@(mapcar (lambda (name)
                 `(setf (getf *arg-form-kinds* ',name) kind))
               names)))

(def-arg-form-kind (:raw)
  :producer (lambda (arg funstate)
              (declare (ignore funstate))
              (mapcar (lambda (bytespec)
                        `(the (unsigned-byte ,(byte-size bytespec))
                           (local-extract ',bytespec)))
                      (arg-fields arg)))
  :checker (lambda (new-arg old-arg)
             (equal (arg-fields new-arg)
                    (arg-fields old-arg))))

(def-arg-form-kind (:sign-extended :unfiltered)
  :producer (lambda (arg funstate)
              (let ((raw-forms (gen-arg-forms arg :raw funstate)))
                (if (and (arg-sign-extend-p arg) (listp raw-forms))
                    (mapcar (lambda (form field)
                              `(the (signed-byte ,(byte-size field))
                                 (sign-extend ,form
                                              ,(byte-size field))))
                            raw-forms
                            (arg-fields arg))
                    raw-forms)))
  :checker (lambda (new-arg old-arg)
             (equal (arg-sign-extend-p new-arg)
                    (arg-sign-extend-p old-arg))))

(defun valsrc-equal (f1 f2)
  (if (null f1)
      (null f2)
      (equal (value-or-source f1)
             (value-or-source f2))))

(def-arg-form-kind (:filtering)
  :producer (lambda (arg funstate)
              (let ((sign-extended-forms
                     (gen-arg-forms arg :sign-extended funstate))
                    (pf (arg-prefilter arg)))
                (if pf
                    (values
                     `(local-filter ,(maybe-listify sign-extended-forms)
                                    ,(source-form pf))
                     t)
                    (values sign-extended-forms nil))))
  :checker (lambda (new-arg old-arg)
             (valsrc-equal (arg-prefilter new-arg) (arg-prefilter old-arg))))

(def-arg-form-kind (:filtered :unadjusted)
  :producer (lambda (arg funstate)
              (let ((pf (arg-prefilter arg)))
                (if pf
                    (values `(local-filtered-value ,(arg-position arg)) t)
                    (gen-arg-forms arg :sign-extended funstate))))
  :checker (lambda (new-arg old-arg)
             (let ((pf1 (arg-prefilter new-arg))
                   (pf2 (arg-prefilter old-arg)))
               (if (null pf1)
                   (null pf2)
                   (= (arg-position new-arg)
                      (arg-position old-arg))))))

(def-arg-form-kind (:adjusted :numeric :unlabelled)
  :producer (lambda (arg funstate)
              (let ((filtered-forms (gen-arg-forms arg :filtered funstate))
                    (use-label (arg-use-label arg)))
                (if (and use-label (not (eq use-label t)))
                    (list
                     `(adjust-label ,(maybe-listify filtered-forms)
                                    ,(source-form use-label)))
                    filtered-forms)))
  :checker (lambda (new-arg old-arg)
             (valsrc-equal (arg-use-label new-arg) (arg-use-label old-arg))))

(def-arg-form-kind (:labelled :final)
  :producer (lambda (arg funstate)
              (let ((adjusted-forms
                     (gen-arg-forms arg :adjusted funstate))
                    (use-label (arg-use-label arg)))
                (if use-label
                    (let ((form (maybe-listify adjusted-forms)))
                      (if (and (not (eq use-label t))
                               (not (atom adjusted-forms))
                               (/= (length adjusted-forms) 1))
                          (pd-error
                           "cannot label a multiple-field argument ~
                              unless using a function: ~S" arg)
                          `((lookup-label ,form))))
                    adjusted-forms)))
  :checker (lambda (new-arg old-arg)
             (let ((lf1 (arg-use-label new-arg))
                   (lf2 (arg-use-label old-arg)))
               (if (null lf1) (null lf2) t))))

;;; This is a bogus kind that's just used to ensure that printers are
;;; compatible...
(def-arg-form-kind (:printed)
  :producer (lambda (&rest noise)
              (declare (ignore noise))
              (pd-error "bogus! can't use the :printed value of an arg!"))
  :checker (lambda (new-arg old-arg)
             (valsrc-equal (arg-printer new-arg) (arg-printer old-arg))))

(defun remember-printer-use (arg funstate)
  (set-arg-temps nil nil arg :printed funstate))

;;; Returns a version of THING suitable for including in an evaluable
;;; position in some form.
(defun source-form (thing)
  (cond ((valsrc-p thing)
         (valsrc-source thing))
        ((functionp thing)
         (pd-error
          "can't dump functions, so function ref form must be quoted: ~S"
          thing))
        ((self-evaluating-p thing)
         thing)
        ((eq (car thing) 'function)
         thing)
        (t
         `',thing)))

;;; Return anything but a VALSRC structure.
(defun value-or-source (thing)
  (if (valsrc-p thing)
      (valsrc-value thing)
      thing))

(defstruct (cached-fun (:conc-name cached-fun-)
                       (:copier nil))
  (funstate nil :type (or null funstate))
  (constraint nil :type list)
  (name nil :type (or null symbol)))

(defun find-cached-fun (cached-funs args constraint)
  (dolist (cached-fun cached-funs nil)
    (let ((funstate (cached-fun-funstate cached-fun)))
      (when (and (equal constraint (cached-fun-constraint cached-fun))
                 (or (null funstate)
                     (funstate-compatible-p funstate args)))
        (return cached-fun)))))

(defmacro !with-cached-fun ((name-var
                             funstate-var
                             cache
                             cache-slot
                             args
                             &key
                             constraint
                             (stem (missing-arg)))
                            &body defun-maker-forms)
  (let ((cache-var (gensym))
        (constraint-var (gensym)))
    `(let* ((,constraint-var ,constraint)
            (,cache-var (find-cached-fun (,cache-slot ,cache)
                                         ,args ,constraint-var)))
       (cond (,cache-var
              (values (cached-fun-name ,cache-var) nil))
             (t
              (let* ((,name-var
                      (symbolicate
                       ,stem
                       (write-to-string (incf (fun-cache-serial-number cache)))))
                     (,funstate-var (make-funstate ,args))
                     (,cache-var
                      (make-cached-fun :name ,name-var
                                       :funstate ,funstate-var
                                       :constraint ,constraint-var)))
                (values ,name-var
                        `(progn
                           ,(progn ,@defun-maker-forms)
                           (eval-when (:compile-toplevel :execute)
                             (push ,,cache-var
                                   (,',cache-slot ',,cache)))))))))))

(defun find-printer-fun (printer-source args cache)
  (if (null printer-source)
      (values nil nil)
      (let ((printer-source (preprocess-printer printer-source args)))
        (!with-cached-fun
           (name funstate cache fun-cache-printers args
                 :constraint printer-source
                 :stem "INST-PRINTER-")
         (make-printer-defun printer-source funstate name)))))

(defun make-printer-defun (source funstate fun-name)
  (let ((printer-form (compile-printer-list source funstate))
        (bindings (make-arg-temp-bindings funstate)))
    `(defun ,fun-name (chunk inst stream dstate)
       (declare (type dchunk chunk)
                (type instruction inst)
                (type stream stream)
                (type disassem-state dstate))
       (macrolet ((local-format-arg (arg fmt)
                    `(funcall (formatter ,fmt) stream ,arg)))
         (flet ((local-tab-to-arg-column ()
                  (tab (dstate-argument-column dstate) stream))
                (local-print-name ()
                  (princ (inst-print-name inst) stream))
                (local-write-char (ch)
                  (write-char ch stream))
                (local-princ (thing)
                  (princ thing stream))
                (local-princ16 (thing)
                  (princ16 thing stream))
                (local-call-arg-printer (arg printer)
                  (funcall printer arg stream dstate))
                (local-call-global-printer (fun)
                  (funcall fun chunk inst stream dstate))
                (local-filtered-value (offset)
                  (declare (type filtered-value-index offset))
                  (aref (dstate-filtered-values dstate) offset))
                (local-extract (bytespec)
                  (dchunk-extract chunk bytespec))
                (lookup-label (lab)
                  (or (gethash lab (dstate-label-hash dstate))
                      lab))
                (adjust-label (val adjust-fun)
                  (funcall adjust-fun val dstate)))
           (declare (ignorable #'local-tab-to-arg-column
                               #'local-print-name
                               #'local-princ #'local-princ16
                               #'local-write-char
                               #'local-call-arg-printer
                               #'local-call-global-printer
                               #'local-extract
                               #'local-filtered-value
                               #'lookup-label #'adjust-label)
                    (inline local-tab-to-arg-column
                            local-princ local-princ16
                            local-call-arg-printer local-call-global-printer
                            local-filtered-value local-extract
                            lookup-label adjust-label))
           (let* ,bindings
             ,@printer-form))))))

(defun preprocess-test (subj form args)
  (multiple-value-bind (subj test)
      (if (and (consp form) (symbolp (car form)) (not (keywordp (car form))))
          (values (car form) (cdr form))
          (values subj form))
    (let ((key (if (consp test) (car test) test))
          (body (if (consp test) (cdr test) nil)))
      (case key
        (:constant
         (if (null body)
             ;; If no supplied constant values, just any constant is ok,
             ;; just see whether there's some constant value in the arg.
             (not
              (null
               (arg-value
                (or (find subj args :key #'arg-name)
                    (pd-error "unknown argument ~S" subj)))))
             ;; Otherwise, defer to run-time.
             form))
        ((:or :and :not)
         (sharing-cons
          form
          subj
          (sharing-cons
           test
           key
           (sharing-mapcar
            (lambda (sub-test)
              (preprocess-test subj sub-test args))
            body))))
        (t form)))))

(defun preprocess-conditionals (printer args)
  (if (atom printer)
      printer
      (case (car printer)
        (:unless
         (preprocess-conditionals
          `(:cond ((:not ,(nth 1 printer)) ,@(nthcdr 2 printer)))
          args))
        (:when
         (preprocess-conditionals `(:cond (,(cdr printer))) args))
        (:if
         (preprocess-conditionals
          `(:cond (,(nth 1 printer) ,(nth 2 printer))
                  (t ,(nth 3 printer)))
          args))
        (:cond
         (sharing-cons
          printer
          :cond
          (sharing-mapcar
           (lambda (clause)
             (let ((filtered-body
                    (sharing-mapcar
                     (lambda (sub-printer)
                       (preprocess-conditionals sub-printer args))
                     (cdr clause))))
               (sharing-cons
                clause
                (preprocess-test (find-first-field-name filtered-body)
                                 (car clause)
                                 args)
                filtered-body)))
           (cdr printer))))
        (quote printer)
        (t
         (sharing-mapcar
          (lambda (sub-printer)
            (preprocess-conditionals sub-printer args))
          printer)))))

;;; Return a version of the disassembly-template PRINTER with
;;; compile-time tests (e.g. :constant without a value), and any
;;; :CHOOSE operators resolved properly for the args ARGS.
;;;
;;; (:CHOOSE Sub*) simply returns the first Sub in which every field
;;; reference refers to a valid arg.
(defun preprocess-printer (printer args)
  (preprocess-conditionals (preprocess-chooses printer args) args))

;;; Return the first non-keyword symbol in a depth-first search of TREE.
(defun find-first-field-name (tree)
  (cond ((null tree)
         nil)
        ((and (symbolp tree) (not (keywordp tree)))
         tree)
        ((atom tree)
         nil)
        ((eq (car tree) 'quote)
         nil)
        (t
         (or (find-first-field-name (car tree))
             (find-first-field-name (cdr tree))))))

(defun preprocess-chooses (printer args)
  (cond ((atom printer)
         printer)
        ((eq (car printer) :choose)
         (pick-printer-choice (cdr printer) args))
        (t
         (sharing-mapcar (lambda (sub) (preprocess-chooses sub args))
                         printer))))

;;;; some simple functions that help avoid consing when we're just
;;;; recursively filtering things that usually don't change

(defun sharing-cons (old-cons car cdr)
  #!+sb-doc
  "If CAR is eq to the car of OLD-CONS and CDR is eq to the CDR, return
  OLD-CONS, otherwise return (cons CAR CDR)."
  (if (and (eq car (car old-cons)) (eq cdr (cdr old-cons)))
      old-cons
      (cons car cdr)))

(defun sharing-mapcar (fun list)
  (declare (type function fun))
  #!+sb-doc
  "A simple (one list arg) mapcar that avoids consing up a new list
  as long as the results of calling FUN on the elements of LIST are
  eq to the original."
  (and list
       (sharing-cons list
                     (funcall fun (car list))
                     (sharing-mapcar fun (cdr list)))))

(defun all-arg-refs-relevant-p (printer args)
  (cond ((or (null printer) (keywordp printer) (eq printer t))
         t)
        ((symbolp printer)
         (find printer args :key #'arg-name))
        ((listp printer)
         (every (lambda (x) (all-arg-refs-relevant-p x args))
                printer))
        (t t)))

(defun pick-printer-choice (choices args)
  (dolist (choice choices
           (pd-error "no suitable choice found in ~S" choices))
    (when (all-arg-refs-relevant-p choice args)
      (return choice))))

(defun compile-printer-list (sources funstate)
  (unless (null sources)
    ;; Coalesce adjacent symbols/strings, and convert to strings if possible,
    ;; since they require less consing to write.
    (do ((el (car sources) (car sources))
         (names nil (cons (strip-quote el) names)))
        ((not (string-or-qsym-p el))
         (when names
           ;; concatenate adjacent strings and symbols
           (let ((string
                  (apply #'concatenate
                         'string
                         (mapcar #'string (nreverse names)))))
             (push (if (some #'alpha-char-p string)
                       `',(make-symbol string) ; Preserve casifying output.
                       string)
                   sources))))
      (pop sources))
    (cons (compile-printer-body (car sources) funstate)
          (compile-printer-list (cdr sources) funstate))))

(defun compile-printer-body (source funstate)
  (cond ((null source)
         nil)
        ((eq source :name)
         `(local-print-name))
        ((eq source :tab)
         `(local-tab-to-arg-column))
        ((keywordp source)
         (pd-error "unknown printer element: ~S" source))
        ((symbolp source)
         (compile-print source funstate))
        ((atom source)
         `(local-princ ',source))
        ((eq (car source) :using)
         (unless (or (stringp (cadr source))
                     (and (listp (cadr source))
                          (eq (caadr source) 'function)))
           (pd-error "The first arg to :USING must be a string or #'function."))
         (compile-print (caddr source) funstate
                        (make-valsrc (eval (cadr source)) (cadr source))))
        ((eq (car source) :plus-integer)
         ;; prints the given field proceed with a + or a -
         (let ((form
                (arg-value-form (arg-or-lose (cadr source) funstate)
                                funstate
                                :numeric)))
           `(progn
              (when (>= ,form 0)
                (local-write-char #\+))
              (local-princ ,form))))
        ((eq (car source) 'quote)
         `(local-princ ,source))
        ((eq (car source) 'function)
         `(local-call-global-printer ,source))
        ((eq (car source) :cond)
         `(cond ,@(mapcar (lambda (clause)
                            `(,(compile-test (find-first-field-name
                                              (cdr clause))
                                             (car clause)
                                             funstate)
                              ,@(compile-printer-list (cdr clause)
                                                      funstate)))
                          (cdr source))))
        ;; :IF, :UNLESS, and :WHEN are replaced by :COND during preprocessing
        (t
         `(progn ,@(compile-printer-list source funstate)))))

(defun compile-print (arg-name funstate &optional printer)
  (let* ((arg (arg-or-lose arg-name funstate))
         (printer (or printer (arg-printer arg)))
         (printer-val (value-or-source printer))
         (printer-src (source-form printer)))
    (remember-printer-use arg funstate)
    (cond ((stringp printer-val)
           `(local-format-arg ,(arg-value-form arg funstate) ,printer-val))
          ((vectorp printer-val)
           `(local-princ
             (aref ,printer-src
                   ,(arg-value-form arg funstate :numeric))))
          ((or (functionp printer-val)
               (and (consp printer-val) (eq (car printer-val) 'function)))
           `(local-call-arg-printer ,(arg-value-form arg funstate)
                                    ,printer-src))
          ((or (null printer-val) (eq printer-val t))
           `(,(if (arg-use-label arg) 'local-princ16 'local-princ)
             ,(arg-value-form arg funstate)))
          (t
           (pd-error "illegal printer: ~S" printer-src)))))

(defun string-or-qsym-p (thing)
  (or (stringp thing)
      (and (consp thing)
           (eq (car thing) 'quote)
           (or (stringp (cadr thing))
               (symbolp (cadr thing))))))

(defun strip-quote (thing)
  (if (and (consp thing) (eq (car thing) 'quote))
      (cadr thing)
      thing))

(defun compare-fields-form (val-form-1 val-form-2)
  (flet ((listify-fields (fields)
           (cond ((symbolp fields) fields)
                 ((every #'constantp fields) `',fields)
                 (t `(list ,@fields)))))
    (cond ((or (symbolp val-form-1) (symbolp val-form-2))
           `(equal ,(listify-fields val-form-1)
                   ,(listify-fields val-form-2)))
          (t
           `(and ,@(mapcar (lambda (v1 v2) `(= ,v1 ,v2))
                           val-form-1 val-form-2))))))

(defun compile-test (subj test funstate)
  (when (and (consp test) (symbolp (car test)) (not (keywordp (car test))))
    (setf subj (car test)
          test (cdr test)))
  (let ((key (if (consp test) (car test) test))
        (body (if (consp test) (cdr test) nil)))
    (cond ((null key)
           nil)
          ((eq key t)
           t)
          ((eq key :constant)
           (let* ((arg (arg-or-lose subj funstate))
                  (fields (arg-fields arg))
                  (consts body))
             (when (not (= (length fields) (length consts)))
               (pd-error "The number of constants doesn't match number of ~
                          fields in: (~S :constant~{ ~S~})"
                         subj body))
             (compare-fields-form (gen-arg-forms arg :numeric funstate)
                                  consts)))
          ((eq key :positive)
           `(> ,(arg-value-form (arg-or-lose subj funstate) funstate :numeric)
               0))
          ((eq key :negative)
           `(< ,(arg-value-form (arg-or-lose subj funstate) funstate :numeric)
               0))
          ((eq key :same-as)
           (let ((arg1 (arg-or-lose subj funstate))
                 (arg2 (arg-or-lose (car body) funstate)))
             (unless (and (= (length (arg-fields arg1))
                             (length (arg-fields arg2)))
                          (every (lambda (bs1 bs2)
                                   (= (byte-size bs1) (byte-size bs2)))
                                 (arg-fields arg1)
                                 (arg-fields arg2)))
               (pd-error "can't compare differently sized fields: ~
                          (~S :same-as ~S)" subj (car body)))
             (compare-fields-form (gen-arg-forms arg1 :numeric funstate)
                                  (gen-arg-forms arg2 :numeric funstate))))
          ((eq key :or)
           `(or ,@(mapcar (lambda (sub) (compile-test subj sub funstate))
                          body)))
          ((eq key :and)
           `(and ,@(mapcar (lambda (sub) (compile-test subj sub funstate))
                           body)))
          ((eq key :not)
           `(not ,(compile-test subj (car body) funstate)))
          ((and (consp key) (null body))
           (compile-test subj key funstate))
          (t
           (pd-error "bogus test-form: ~S" test)))))

(defun find-labeller-fun (args cache)
  (let ((labelled-fields
         (mapcar #'arg-name (remove-if-not #'arg-use-label args))))
    (if (null labelled-fields)
        (values nil nil)
        (!with-cached-fun
            (name funstate cache fun-cache-labellers args
             :stem "INST-LABELLER-"
             :constraint labelled-fields)
          (let ((labels-form 'labels))
            (dolist (arg args)
              (when (arg-use-label arg)
                (setf labels-form
                      `(let ((labels ,labels-form)
                             (addr
                              ,(arg-value-form arg funstate :adjusted nil)))
                         ;; if labeler didn't return an integer, it isn't a label
                         (if (or (not (integerp addr)) (assoc addr labels))
                             labels
                             (cons (cons addr nil) labels))))))
            `(defun ,name (chunk labels dstate)
               (declare (type list labels)
                        (type dchunk chunk)
                        (type disassem-state dstate))
               (flet ((local-filtered-value (offset)
                        (declare (type filtered-value-index offset))
                        (aref (dstate-filtered-values dstate) offset))
                      (local-extract (bytespec)
                        (dchunk-extract chunk bytespec))
                      (adjust-label (val adjust-fun)
                        (funcall adjust-fun val dstate)))
                 (declare (ignorable #'local-filtered-value #'local-extract
                                     #'adjust-label)
                          (inline local-filtered-value local-extract
                                  adjust-label))
                 (let* ,(make-arg-temp-bindings funstate)
                   ,labels-form))))))))

(defun find-prefilter-fun (args cache)
  (let ((filtered-args (mapcar #'arg-name
                               (remove-if-not #'arg-prefilter args))))
    (if (null filtered-args)
        (values nil nil)
        (!with-cached-fun
            (name funstate cache fun-cache-prefilters args
             :stem "INST-PREFILTER-"
             :constraint filtered-args)
          (collect ((forms))
            (dolist (arg args)
              (let ((pf (arg-prefilter arg)))
                (when pf
                  (forms
                   `(setf (local-filtered-value ,(arg-position arg))
                          ,(maybe-listify
                            (gen-arg-forms arg :filtering funstate)))))
                ))
            `(defun ,name (chunk dstate)
               (declare (type dchunk chunk)
                        (type disassem-state dstate))
               (flet (((setf local-filtered-value) (value offset)
                       (declare (type filtered-value-index offset))
                       (setf (aref (dstate-filtered-values dstate) offset)
                             value))
                      (local-filter (value filter)
                                    (funcall filter value dstate))
                      (local-extract (bytespec)
                                     (dchunk-extract chunk bytespec)))
                (declare (ignorable #'local-filter #'local-extract)
                         (inline (setf local-filtered-value)
                                 local-filter local-extract))
                ;; Use them for side effects only.
                (let* ,(make-arg-temp-bindings funstate)
                  ,@(forms)))))))))

(defun compute-mask-id (args)
  (let ((mask dchunk-zero)
        (id dchunk-zero))
    (dolist (arg args (values mask id))
      (let ((av (arg-value arg)))
        (when av
          (do ((fields (arg-fields arg) (cdr fields))
               (values (if (atom av) (list av) av) (cdr values)))
              ((null fields))
            (let ((field-mask (dchunk-make-mask (car fields))))
              (when (/= (dchunk-and mask field-mask) dchunk-zero)
                (pd-error "The field ~S in arg ~S overlaps some other field."
                          (car fields)
                          (arg-name arg)))
              (dchunk-insertf id (car fields) (car values))
              (dchunk-orf mask field-mask))))))))

(defun install-inst-flavors (name flavors)
  (setf (gethash name *disassem-insts*)
        flavors))

#!-sb-fluid (declaim (inline bytes-to-bits))
(declaim (maybe-inline sign-extend aligned-p align tab tab0))

(defun bytes-to-bits (bytes)
  (declare (type disassem-length bytes))
  (* bytes sb!vm:n-byte-bits))

(defun bits-to-bytes (bits)
  (declare (type disassem-length bits))
  (multiple-value-bind (bytes rbits)
      (truncate bits sb!vm:n-byte-bits)
    (when (not (zerop rbits))
      (error "~W bits is not a byte-multiple." bits))
    bytes))

(defun sign-extend (int size)
  (declare (type integer int)
           (type (integer 0 128) size))
  (if (logbitp (1- size) int)
      (dpb int (byte size 0) -1)
      int))

;;; Is ADDRESS aligned on a SIZE byte boundary?
(defun aligned-p (address size)
  (declare (type address address)
           (type alignment size))
  (zerop (logand (1- size) address)))

;;; Return ADDRESS aligned *upward* to a SIZE byte boundary.
(defun align (address size)
  (declare (type address address)
           (type alignment size))
  (logandc1 (1- size) (+ (1- size) address)))

(defun tab (column stream)
  (funcall (formatter "~V,1t") stream column)
  nil)
(defun tab0 (column stream)
  (funcall (formatter "~V,0t") stream column)
  nil)

(defun princ16 (value stream)
  (write value :stream stream :radix t :base 16 :escape nil))

(defun read-signed-suffix (length dstate)
  (declare (type (member 8 16 32 64) length)
           (type disassem-state dstate)
           (optimize (speed 3) (safety 0)))
  (sign-extend (read-suffix length dstate) length))

(defstruct (storage-info (:copier nil))
  (groups nil :type list)               ; alist of (name . location-group)
  (debug-vars #() :type vector))

(defstruct (segment (:conc-name seg-)
                    (:constructor %make-segment)
                    (:copier nil))
  (sap-maker (missing-arg)
             :type (function () sb!sys:system-area-pointer))
  ;; Length in bytes of the range of memory covered by this segment.
  (length 0 :type disassem-length)
  ;; Length of the memory range excluding any trailing untagged data.
  ;; Defaults to 'length' but could be shorter.
  ;; FIXME: can opcodes-length really be shorter? Nothing ever alters it.
  (opcodes-length 0 :type disassem-length)
  (virtual-location 0 :type address)
  (storage-info nil :type (or null storage-info))
  ;; KLUDGE: CODE-COMPONENT is not a type the host understands
  #-sb-xc-host (code nil :type (or null sb!kernel:code-component))
  (unboxed-data-range nil :type (or null (cons fixnum fixnum)))
  (hooks nil :type list))

;;; All state during disassembly. We store some seemingly redundant
;;; information so that we can allow garbage collect during disassembly and
;;; not get tripped up by a code block being moved...
(defstruct (disassem-state (:conc-name dstate-)
                           (:constructor %make-dstate)
                           (:copier nil))
  ;; offset of current pos in segment
  (cur-offs 0 :type offset)
  ;; offset of next position
  (next-offs 0 :type offset)
  ;; a sap pointing to our segment
  (segment-sap nil :type (or null sb!sys:system-area-pointer))
  ;; the current segment
  (segment nil :type (or null segment))
  ;; what to align to in most cases
  (alignment sb!vm:n-word-bytes :type alignment)
  (byte-order :little-endian
              :type (member :big-endian :little-endian))
  ;; for user code to hang stuff off of
  (properties nil :type list)
  ;; for user code to hang stuff off of, cleared each time after a
  ;; non-prefix instruction is processed
  (inst-properties nil :type list)
  (filtered-values (make-array max-filtered-value-index)
                   :type filtered-value-vector)
  ;; used for prettifying printing
  (addr-print-len nil :type (or null (integer 0 20)))
  (argument-column 0 :type column)
  ;; to make output look nicer
  (output-state :beginning
                :type (member :beginning
                              :block-boundary
                              nil))

  ;; alist of (address . label-number)
  (labels nil :type list)
  ;; same as LABELS slot data, but in a different form
  (label-hash (make-hash-table) :type hash-table)
  ;; list of function
  (fun-hooks nil :type list)

  ;; alist of (address . label-number), popped as it's used
  (cur-labels nil :type list)
  ;; OFFS-HOOKs, popped as they're used
  (cur-offs-hooks nil :type list)

  ;; for the current location
  (notes nil :type list)

  ;; currently active source variables
  (current-valid-locations nil :type (or null (vector bit))))
(def!method print-object ((dstate disassem-state) stream)
  (print-unreadable-object (dstate stream :type t)
    (format stream
            "+~W~@[ in ~S~]"
            (dstate-cur-offs dstate)
            (dstate-segment dstate))))

;;; Return the absolute address of the current instruction in DSTATE.
(defun dstate-cur-addr (dstate)
  (the address (+ (seg-virtual-location (dstate-segment dstate))
                  (dstate-cur-offs dstate))))

;;; Return the absolute address of the next instruction in DSTATE.
(defun dstate-next-addr (dstate)
  (the address (+ (seg-virtual-location (dstate-segment dstate))
                  (dstate-next-offs dstate))))

;;; Get the value of the property called NAME in DSTATE. Also SETF'able.
;;;
;;; KLUDGE: The associated run-time machinery for this is in
;;; target-disassem.lisp (much later). This is here just to make sure
;;; it's defined before it's used. -- WHN ca. 19990701
(defmacro dstate-get-prop (dstate name)
  `(getf (dstate-properties ,dstate) ,name))

;;; Push NAME on the list of instruction properties in DSTATE.
(defun dstate-put-inst-prop (dstate name)
  (push name (dstate-inst-properties dstate)))

;;; Return non-NIL if NAME is on the list of instruction properties in
;;; DSTATE.
(defun dstate-get-inst-prop (dstate name)
  (member name (dstate-inst-properties dstate) :test #'eq))
