;;; nyacc/lang/c99/c99eval.scm - evaluate constant expressions

;; Copyright (C) 2018-2020 Matthew R. Wette
;;
;; This library is free software; you can redistribute it and/or
;; modify it under the terms of the GNU Lesser General Public
;; License as published by the Free Software Foundation; either
;; version 3 of the License, or (at your option) any later version.
;;
;; This library is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
;; Lesser General Public License for more details.
;;
;; You should have received a copy of the GNU Lesser General Public License
;; along with this library; if not, see <http://www.gnu.org/licenses/>.

;;; Code:

(define-module (nyacc lang c99 cxeval)
  #:export (parse-c99-cx
	    eval-c99-cx
	    eval-sizeof-type
	    eval-sizeof-expr
	    sizeof-mtail
	    )
  #:use-module (nyacc lalr)
  #:use-module (nyacc parse)
  #:use-module (nyacc lex)
  #:use-module (nyacc util)
  #:use-module ((nyacc lang util) #:select (make-tl tl-append tl->list))
  #:use-module (nyacc lang sx-util)
  #:use-module (nyacc lang arch-info)
  #:use-module (nyacc lang c99 cpp)
  #:use-module (nyacc lang c99 parser)
  #:use-module (nyacc lang c99 munge-base)
  #:use-module (rnrs arithmetic bitwise)
  #:use-module (system foreign)
  #:use-module (ice-9 match))

(use-modules (ice-9 pretty-print))
(define (sferr fmt . args)
  (apply simple-format (current-error-port) fmt args))
(define (pperr exp)
  (pretty-print exp (current-error-port) #:per-line-prefix "  "))

(define ffi-type-map
  `(("void" . ,void) ("float" . ,float) ("double" . ,double) ("short" . ,short)
    ("short int" . ,short) ("signed short" . ,short)
    ("signed short int" . ,short) ("int" . ,int) ("signed" . ,int)
    ("signed int" . ,int) ("long" . ,long) ("long int" . ,long)
    ("signed long" . ,long) ("signed long int" . ,long)
    ("unsigned short int" . ,unsigned-short)
    ("unsigned short" . ,unsigned-short)
    ("unsigned int" . ,unsigned-int) ("unsigned" . ,unsigned-int)
    ("unsigned long int" . ,unsigned-long) ("unsigned long" . ,unsigned-long)
    ("char" . ,int8) ("signed char" . ,int8) ("unsigned char" . ,uint8)
    ("wchar_t" . ,int) ("char16_t" . ,int16) ("char32_t" . ,int32)
    ("long long" . ,long) ("long long int" . ,long)
    ("signed long long" . ,long) ("signed long long int" . ,long)
    ("unsigned long long" . ,unsigned-long)
    ("unsigned long long int" . ,unsigned-long) ("_Bool" . ,int8)
    ("size_t" . ,size_t)))

(define (sizeof-type name)
  (or (and=> (assoc-ref ffi-type-map name) sizeof)
      (throw 'c99-error "bad type")))

;; (string "abc" "dev")
(define (sizeof-string-const value)
  #f)

(include-from-path "nyacc/lang/c99/mach.d/c99cx-act.scm")
(include-from-path "nyacc/lang/c99/mach.d/c99cx-tab.scm")

(define c99cx-raw-parser
  (make-lalr-parser
   (acons 'act-v c99cx-act-v c99cx-tables)))

(define gen-c99cx-lexer
  (let* ((reader (make-comm-reader '(("/*" . "*/"))))
	 (comm-skipper (lambda (ch) (reader ch #f))))
    (make-lexer-generator c99cx-mtab
			  #:comm-skipper comm-skipper
			  #:chlit-reader read-c-chlit
			  #:num-reader read-c-num)))

(define (parse-c99cx text)
  (with-throw-handler
      'c99-error
    (lambda ()
      (with-input-from-string text
	(lambda () (c99cx-raw-parser (gen-c99cx-lexer)))))
    (lambda (key fmt . args)
      (apply throw 'cpp-error fmt args))))

(define* (expand-typename typename udict #:key (namer def-namer))
  (let* ((decl `(udecl (decl-spec-list
			(type-spec (typename ,typename)))
		       (declr (ident (namer)))))
	 (xdecl (expand-typerefs decl udict))
	 (xname (and xdecl (sx-ref* xdecl 1 1 1 1))))
    xname))

(define (sizeof-mtail mtail arch)
  ;; (decl attr specl (declr-list declr1 declr2 ...))
  ;; => ((decl attr specl declr1) (decl attr specl declr2) ...)
  (define (splitup-decl decl)
    (let ((tag (sx-tag decl)) (attr (sx-attr decl))
	  (specl (sx-ref decl 1)) (dclrl (sx-ref decl 2)))
      (map (lambda (declr) (sx-list tag attr specl declr)) (sx-tail dclrl))))

  ;; Update running struct size (rs) given new item s and a.
  (define (incr-size s a rs)
    (+ s (* a (quotient (+ rs (1- a)) a))))

  ;; Update running union size (rs) given new item s and a.
  (define (maxi-size s a rs)
    (max s rs))

  (define (exec/decl decl size base-align update)
    (let ((mtail (sx-tail (sx-find 'type-spec (sx-ref decl 1))))
	  (declrs (sx-tail (sx-ref decl 2))))
      (let loop ((size size) (base-align base-align) (declrs declrs))
	(if (null? declrs)
	    (values size base-align)
	    (call-with-values
		(lambda ()
		  (sizeof-mtail
		   (cdr (m-unwrap-declr (car declrs) mtail)) arch))
	      (lambda (elt-size elt-align)
		(loop (update elt-size elt-align size)
		      (max elt-align base-align) (cdr declrs))))))))

  (define (incr/decl decl size base-align)
    (exec/decl decl size base-align incr-size))
  
  (define (maxi/decl decl size base-align)
    (exec/decl decl size base-align maxi-size))

  (match mtail
    (`((pointer-to) . ,rest)
     (values (sizeof-basetype '* arch) (alignof-basetype '* arch)))
    (`((fixed-type ,name))
     (values (sizeof-basetype name arch) (alignof-basetype name arch)))
    (`((float-type ,name))
     (values (sizeof-basetype name arch) (alignof-basetype name arch)))
    (`((array-of ,size) . ,rest)
     (let ((mult (eval-c99-cx size)))
       (call-with-values
	   (lambda () (sizeof-mtail rest arch))
	 (lambda (size align)
	   (values (* mult size) align)))))

    (`((struct-def (field-list . ,fields)))
     (let loop ((size 0) (align 0) (flds fields))
       (cond
	((null? flds) (values (incr-size 0 align size) align))
	((eq? 'comp-decl (sx-tag (car flds)))
	 (call-with-values
	     (lambda () (incr/decl (car flds) size align))
	   (lambda (size align)
	     (loop size align (cdr flds)))))
	(else (loop size align (cdr flds))))))

    (`((union-def (field-list . ,fields)))
     (let loop ((size 0) (align 0) (flds fields))
       (cond
	((null? flds) (values (incr-size 0 align size) align))
	((eq? 'comp-decl (sx-tag (car flds)))
	 (call-with-values
	     (lambda () (maxi/decl (car flds) size align))
	   (lambda (size align)
	     (loop size align (cdr flds)))))
	(else (loop size align (cdr flds))))))

    (`((,(or 'enum-ref 'enum-def) . ,rest))
     (values (sizeof-basetype "int" arch) (alignof-basetype "int" arch)))

    (_ (sferr "c99/eval-sizeof-mtail: missed\n") (pperr mtail)
       (throw 'c99-error "coding error"))))

(define* (sizeof-specl/declr specl declr #:optional (udict '()) #:key arch)
  (let* ((udecl `(udecl ,specl ,declr))
	 (xdecl (expand-typerefs udecl udict))
	 (mdecl (udecl->mdecl xdecl)))
    (sizeof-mtail (cdr mdecl) arch)))

(define (trim-mtail mtail)
  (case (caar mtail)
    ((extern) (trim-mtail (cdr mtail)))
    ((comment) (trim-mtail (cdr mtail)))
    ((initzer) (trim-mtail (cdr mtail)))
    (else mtail)))

;; @deffn {Procedure} eval-sizeof-type tree [udict]
;; => (values sizeof-val align-of)
;; @end deffn
(define* (eval-sizeof-type tree #:optional (udict '()) #:key arch)
  (let* ((type-name (sx-ref tree 1))
	 (specl (sx-ref type-name 1))
	 (declr (or (sx-ref type-name 2) '(param-declr))))
    (sizeof-specl/declr specl declr udict #:arch arch)))

;; @deffn {Procedure} eval-sizeof-expr tree [udict]
;; => (values sizeof-val align-of)
;; @end deffn
(define* (eval-sizeof-expr tree #:optional (udict '()) #:key arch)

  (define (sizeof-literal tree)
    (sx-match tree
      ((p-expr ,expr) (sizeof-literal expr))
      ((string . ,string-list)
       (values
	(let loop ((sl string-list))
	  (if (null? sl) 0
	      (+ (string-length (car sl)) (loop (cdr sl)))))
	1))
      (,_ #f)))

  (define (gen-mtail tree)
    (sx-match tree
      ((sizeof-expr ,expr) (gen-mtail expr))
      ((p-expr ,expr) (gen-mtail expr))
      ((ident ,name)
       (let* ((udecl (assoc-ref udict name))
	      (xdecl (and udecl (expand-typerefs udecl udict)))
	      (mdecl (and xdecl (udecl->mdecl xdecl))))
	 (if (not mdecl) (throw 'c99-error "not found: ~S" name))
	 (trim-mtail (cdr mdecl))))
      ((array-ref ,elt ,expr)
       (let ((mtail (gen-mtail expr)))
	 (match mtail
	   (`((array-of ,size) . ,rest) rest)
	   (_ (throw 'c99-error "cxeval: can't ref array")))))
      ((de-ref ,expr)
       (let ((mtail (gen-mtail expr)))
	 (match mtail
	   (`((pointer-to) . ,rest) rest)
	   (_ (throw 'c99-error "cxeval: can't de-ref")))))
      (,_ (throw 'c99-error "cxeval: can't sizeof ~S" (list tree)))))

  (or
   (sizeof-literal tree)
   (sizeof-mtail (gen-mtail tree) arch)))
      

;; @deffn {Procedure} eval-c99-cx tree [udict] [#:fail-proc fail-proc]
;; Evaluate the constant expression or return #f
;; If @code{fail-proc} is provided it is called with the tree that could not
;; be parsed.  If provided, it should return @code{#f} or throw an exception.
;; @end deffn
(define* (eval-c99-cx tree #:optional udict ddict #:key fail-proc)

  (define (fail fmt . args)
    (and fail-proc (apply fail-proc fmt args)))

  (define (ddict-lookup name)
    (let ((repl (assoc-ref ddict name)))
      (cond
       ((not repl) #f)
       ((pair? repl) #f)
       ((string=? name repl) #f)
       (else repl))))
  
  (define (eval-ident sx)
    (let* ((name (sx-ref sx 1)) (repl (ddict-lookup name)))
      (and (string? repl) (string->number repl))))
  
  (define (uop op ex)
    (and op ex (op ex)))
  
  (define (bop op lt rt)
    (and op lt rt (op lt rt)))

  (letrec
      ((ev (lambda (ex ix) (eval-expr (sx-ref ex ix))))
       (ev1 (lambda (ex) (ev ex 1)))	; eval expr in arg 1
       (ev2 (lambda (ex) (ev ex 2)))	; eval expr in arg 2
       (ev3 (lambda (ex) (ev ex 3)))	; eval expr in arg 3

       (eval-expr
	(lambda (tree)
	  (case (sx-tag tree)
	    ((fixed) (string->number (cnumstr->scm (sx-ref tree 1))))
	    ((float) (string->number (cnumstr->scm (sx-ref tree 1))))
	    ((char) (char->integer (string-ref (sx-ref tree 1) 0)))
	    ((string) (string-join (sx-tail tree 1) ""))
	    ((pre-inc post-inc) (uop 1+ (ev1 tree)))
	    ((pre-dec post-dec) (uop 1- (ev1 tree)))
	    ((pos) (and tree (ev1 tree)))
	    ((neg) (uop - (ev1 tree)))
	    ((not) (and tree (if (equal? 0 (ev1 tree)) 1 0)))
	    ((mul) (bop * (ev1 tree) (ev2 tree)))
	    ((div) (bop / (ev1 tree) (ev2 tree)))
	    ((mod) (bop modulo (ev1 tree) (ev2 tree)))
	    ((add) (bop + (ev1 tree) (ev2 tree)))
	    ((sub) (bop - (ev1 tree) (ev2 tree)))
	    ((lshift) (bop bitwise-arithmetic-shift-left (ev1 tree) (ev2 tree)))
	    ((rshift) (bop bitwise-arithmetic-shift-right (ev1 tree) (ev2 tree)))
	    ((lt) (if (bop < (ev1 tree) (ev2 tree)) 1 0))
	    ((le) (if (bop <= (ev1 tree) (ev2 tree)) 1 0))
	    ((gt) (if (bop > (ev1 tree) (ev2 tree)) 1 0))
	    ((ge) (if (bop >= (ev1 tree) (ev2 tree)) 1 0))
	    ((eq) (if (bop = (ev1 tree) (ev2 tree)) 1 0))
	    ((ne) (if (bop = (ev1 tree) (ev2 tree)) 0 1))
	    ((bitwise-not) (uop lognot (ev1 tree)))
  	    ((bitwise-or) (bop logior (ev1 tree) (ev2 tree)))
	    ((bitwise-xor) (bop logxor (ev1 tree) (ev2 tree)))
	    ((bitwise-and) (bop logand (ev1 tree) (ev2 tree)))
	    ;;
	    ((or)
	     (let ((e1 (ev1 tree)) (e2 (ev2 tree)))
	       (if (and e1 e2) (if (and (zero? e1) (zero? e2)) 0 1) #f)))
	    ((and)
	     (let ((e1 (ev1 tree)) (e2 (ev2 tree)))
	       (if (and e1 e2) (if (or (zero? e1) (zero? e2)) 0 1) #f)))
	    ((cond-expr)
	     (let ((e1 (ev1 tree)) (e2 (ev2 tree)) (e3 (ev3 tree)))
	       (if (and e1 e2 e3) (if (zero? e1) e3 e2) #f)))
	    ;;
	    ((sizeof-type)
	     (catch 'c99-error
	       (lambda ()
		 (call-with-values (lambda () (eval-sizeof-type tree udict))
		   (lambda (size align) size)))
	       (lambda (key fmt . args) (apply fail fmt args))))
	    ((sizeof-expr)
	     (catch 'c99-error
	       (lambda ()
		 (call-with-values (lambda () (eval-sizeof-expr tree udict))
		   (lambda (size align) size)))
	       (lambda (key fmt . args) (apply fail fmt args))))
	    ((ident) (or (eval-ident tree)
			 (fail "cannot resolve identifier ~S" (sx-ref tree 1))))
	    ((p-expr) (ev1 tree))
	    ((cast) (ev2 tree))
	    ((fctn-call) #f)		; assume not constant
	    ((ref-to) #f)		; assume address not useful
	    ;;
	    ;; TODO 
	    ((comp-lit) (fail "cxeval: comp-lit not implemented"))
	    ((comma-expr) (fail "cxeval: comma-expr not implemented"))
	    ((i-sel) (fail "cxeval: i-sel not implemented"))
	    ((d-sel) (fail "cxeval: d-sel not implemented"))
	    ((array-ref) (fail "cxeval: array-ref not implemented"))
	    ;; 
	    (else
	     (sferr "eval-c99-cx:") (pperr tree)
	     (throw 'c99-error "eval-c99-cx: coding error"))))))

    (eval-expr tree)))
 
;; --- last line ---
