mdw@git.distorted.org.uk Git - sod/blob - src/codegen-proto.lisp

   1 ;;; -*-lisp-*-
   2 ;;;
   3 ;;; Code generation protocol
   4 ;;;
   5 ;;; (c) 2009 Straylight/Edgeware
   6 ;;;
   7
   8 ;;;----- Licensing notice ---------------------------------------------------
   9 ;;;
  10 ;;; This file is part of the Sensble Object Design, an object system for C.
  11 ;;;
  12 ;;; SOD is free software; you can redistribute it and/or modify
  13 ;;; it under the terms of the GNU General Public License as published by
  14 ;;; the Free Software Foundation; either version 2 of the License, or
  15 ;;; (at your option) any later version.
  16 ;;;
  17 ;;; SOD is distributed in the hope that it will be useful,
  18 ;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  19 ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20 ;;; GNU General Public License for more details.
  21 ;;;
  22 ;;; You should have received a copy of the GNU General Public License
  23 ;;; along with SOD; if not, write to the Free Software Foundation,
  24 ;;; Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  25
  26 (cl:in-package #:sod)
  27
  28 ;;;--------------------------------------------------------------------------
  29 ;;; Temporary names.
  30
  31 ;; Protocol.
  32
  33 (export 'format-temporary-name)
  34 (defgeneric format-temporary-name (var stream)
  35   (:documentation
  36    "Write the name of a temporary variable VAR to STREAM."))
  37
  38 (export 'var-in-use-p)
  39 (defgeneric var-in-use-p (var)
  40   (:documentation
  41    "Answer whether VAR is currently being used.  See `with-temporary-var'.")
  42   (:method (var)
  43     "Non-temporary variables are always in use."
  44     (declare (ignore var))
  45     t))
  46 (defgeneric (setf var-in-use-p) (value var)
  47   (:documentation
  48    "Record whether VAR is currently being used.  See `with-temporary-var'."))
  49
  50 ;; Root class.
  51
  52 (export '(temporary-name temp-tag))
  53 (defclass temporary-name ()
  54   ((tag :initarg :tag :reader temp-tag))
  55   (:documentation
  56    "Base class for temporary variable and argument names."))
  57
  58 ;; Important temporary names.
  59
  60 (export '(*sod-ap* *sod-master-ap*))
  61 (defparameter *sod-ap*
  62   (make-instance 'temporary-name :tag "sod__ap"))
  63 (defparameter *sod-master-ap*
  64   (make-instance 'temporary-name :tag "sod__master_ap"))
  65 (defparameter *sod-tmp-ap*
  66   (make-instance 'temporary-name :tag "sod__tmp_ap"))
  67 (defparameter *sod-tmp-val*
  68   (make-instance 'temporary-name :tag "sod__t"))
  69
  70 ;;;--------------------------------------------------------------------------
  71 ;;; Instructions.
  72
  73 ;; Classes.
  74
  75 (export 'inst)
  76 (defclass inst () ()
  77   (:documentation
  78    "A base class for instructions.
  79
  80    An `instruction' is anything which might be useful to string into a code
  81    generator.  Both statements and expressions can be represented by trees of
  82    instructions.  The `definst' macro is a convenient way of defining new
  83    instructions.
  84
  85    The only important protocol for instructions is output, which is achieved
  86    by calling `print-object' with `*print-escape*' nil.
  87
  88    This doesn't really do very much, but it acts as a handy marker for
  89    instruction subclasses."))
  90
  91 (export 'inst-metric)
  92 (defgeneric inst-metric (inst)
  93   (:documentation
  94    "Returns a `metric' describing how complicated INST is.
  95
  96    The default metric of an inst node is simply 1; `inst' subclasses
  97    generated by `definst' (q.v.) have an automatically generated method which
  98    returns one plus the sum of the metrics of the node's children.
  99
 100    This isn't intended to be a particularly rigorous definition.  Its purpose
 101    is to allow code generators to make decisions about inlining or calling
 102    code fairly simply.")
 103   (:method ((inst t))
 104     (declare (ignore inst))
 105     1)
 106   (:method ((inst null))
 107     (declare (ignore inst))
 108     1)
 109   (:method ((inst list))
 110     (reduce #'+ inst :key #'inst-metric)))
 111
 112 ;; Instruction definition.
 113
 114 (export 'definst)
 115 (defmacro definst (code (streamvar &key export) args &body body)
 116   "Define an instruction type and describe how to output it.
 117
 118    An `inst' can represent any structured piece of output syntax: a
 119    statement, expression or declaration, for example.  This macro defines the
 120    following things:
 121
 122      * A class `CODE-inst' to represent the instruction.
 123
 124      * Instance slots named after the ARGS, with matching keyword initargs,
 125        and `inst-ARG' readers.
 126
 127      * A constructor `make-CODE-inst' which accepts the ARGS (in order, not
 128        with keywords) as arguments and returns a fresh instance.
 129
 130      * A print method, which prints a diagnostic dump if `*print-escape*' is
 131        set, or invokes the BODY (with STREAMVAR bound to the output stream)
 132        otherwise.  The BODY is expected to produce target code at this
 133        point.
 134
 135    If EXPORT is non-nil, then export the `CODE-inst' and `make-CODE-inst'
 136    symbols."
 137
 138   (let ((inst-var (gensym "INST"))
 139         (class-name (symbolicate code '-inst))
 140         (constructor-name (symbolicate 'make- code '-inst))
 141         (keys (mapcar (lambda (arg) (intern (symbol-name arg) :keyword))
 142                       args)))
 143     `(progn
 144        (defclass ,class-name (inst)
 145          ,(mapcar (lambda (arg key)
 146                     `(,arg :initarg ,key :reader ,(symbolicate 'inst- arg)))
 147                   args keys))
 148        (defun ,constructor-name (,@args)
 149          (make-instance ',class-name ,@(mappend #'list keys args)))
 150        (defmethod inst-metric ((,inst-var ,class-name))
 151          (with-slots (,@args) ,inst-var
 152            (+ 1 ,@(mapcar (lambda (arg) `(inst-metric ,arg)) args))))
 153        (defmethod print-object ((,inst-var ,class-name) ,streamvar)
 154          (with-slots (,@args) ,inst-var
 155            (if *print-escape*
 156                (print-unreadable-object (,inst-var ,streamvar :type t)
 157                  (format stream "~@<~@{~S ~@_~S~^ ~_~}~:>"
 158                          ,@(mappend #'list keys args)))
 159                (block ,code ,@body))))
 160        ,@(and export `((export '(,class-name ,constructor-name
 161                                  ,@(mapcar (lambda (arg)
 162                                              (symbolicate 'inst- arg))
 163                                            args)))))
 164        ',code)))
 165
 166 ;; Important instruction classes.
 167
 168 ;; HACK: use a gensym for the `expr' and `type' slots to avoid leaking the
 169 ;; slot names, since the symbol `expr' is exported from our package and
 170 ;; `type' belongs to the `common-lisp' package.
 171
 172 (definst var (stream :export t) (name #1=#:type init)
 173   (pprint-c-type #1# stream name)
 174   (when init
 175     (format stream " = ~A" init))
 176   (write-char #\; stream))
 177 (definst set (stream :export t) (var #1=#:expr)
 178   (format stream "~@<~A = ~@_~2I~A;~:>" var #1#))
 179 (definst update (stream :export t) (var op #1=#:expr)
 180   (format stream "~@<~A ~A= ~@_~2I~A;~:>" var op #1#))
 181 (definst return (stream :export t) (#1=#:expr)
 182   (format stream "return~@[ (~A)~];" #1#))
 183 (definst break (stream :export t) ()
 184   (format stream "break;"))
 185 (definst continue (stream :export t) ()
 186   (format stream "continue;"))
 187 (definst expr (stream :export t) (#1=#:expr)
 188   (format stream "~A;" #1#))
 189 (definst block (stream :export t) (decls body)
 190   (format stream "{~:@_~@<  ~2I~@[~{~A~:@_~}~:@_~]~{~A~^~:@_~}~:>~:@_}"
 191           decls body))
 192 (definst function (stream :export t) (name #1=#:type body)
 193   (pprint-logical-block (stream nil)
 194     (princ "static " stream)
 195     (pprint-c-type #1# stream name)
 196     (format stream "~:@_~A~:@_~:@_" body)))
 197
 198 ;; Formatting utilities.
 199
 200 (defun format-compound-statement* (stream child morep thunk)
 201   "Underlying function for `format-compound-statement'."
 202   (cond ((typep child 'block-inst)
 203          (funcall thunk stream)
 204          (write-char #\space stream)
 205          (princ child stream)
 206          (when morep (write-char #\space stream)))
 207         (t
 208          (pprint-logical-block (stream nil)
 209            (funcall thunk stream)
 210            (write-char #\space stream)
 211            (pprint-indent :block 2 stream)
 212            (pprint-newline :linear stream)
 213            (princ child stream)
 214            (pprint-indent :block 0 stream)
 215            (case morep
 216              (:space
 217               (write-char #\space stream)
 218               (pprint-newline :linear stream))
 219              ((t)
 220               (pprint-newline :mandatory stream)))))))
 221
 222 (export 'format-compound-statement)
 223 (defmacro format-compound-statement
 224     ((stream child &optional morep) &body body)
 225   "Format a compound statement to STREAM.
 226
 227    The introductory material is printed by BODY.  The CHILD is formatted
 228    properly according to whether it's a `block-inst'.  If MOREP is true, then
 229    allow for more stuff following the child."
 230   `(format-compound-statement* ,stream ,child ,morep
 231                                (lambda (,stream) ,@body)))
 232
 233 ;;;--------------------------------------------------------------------------
 234 ;;; Code generation.
 235
 236 ;; Accessors.
 237
 238 (export 'codegen-functions)
 239 (defgeneric codegen-functions (codegen)
 240   (:documentation
 241    "Return the list of `function-inst's of completed functions."))
 242
 243 (export 'ensure-var)
 244 (defgeneric ensure-var (codegen name type &optional init)
 245   (:documentation
 246    "Add a variable to CODEGEN's list.
 247
 248    The variable is called NAME (which should be comparable using `equal' and
 249    print to an identifier) and has the given TYPE.  If INIT is present and
 250    non-nil it is an expression `inst' used to provide the variable with an
 251    initial value."))
 252
 253 (export '(emit-inst emit-insts))
 254 (defgeneric emit-inst (codegen inst)
 255   (:documentation
 256    "Add INST to the end of CODEGEN's list of instructions."))
 257 (defgeneric emit-insts (codegen insts)
 258   (:documentation
 259    "Add a list of INSTS to the end of CODEGEN's list of instructions.")
 260   (:method (codegen insts)
 261     (dolist (inst insts) (emit-inst codegen inst))))
 262
 263 (export '(emit-decl emit-decls))
 264 (defgeneric emit-decl (codegen inst)
 265   (:documentation
 266    "Add INST to the end of CODEGEN's list of declarations."))
 267 (defgeneric emit-decls (codegen insts)
 268   (:documentation
 269    "Add a list of INSTS to the end of CODEGEN's list of declarations."))
 270
 271 (export 'codegen-push)
 272 (defgeneric codegen-push (codegen)
 273   (:documentation
 274    "Pushes the current code generation state onto a stack.
 275
 276    The state consists of the accumulated variables and instructions."))
 277
 278 (export 'codegen-pop)
 279 (defgeneric codegen-pop (codegen)
 280   (:documentation
 281    "Pops a saved state off of the CODEGEN's stack.
 282
 283    Returns the newly accumulated variables and instructions as lists, as
 284    separate values."))
 285
 286 (export 'codegen-add-function)
 287 (defgeneric codegen-add-function (codegen function)
 288   (:documentation
 289    "Adds a function to CODEGEN's list.
 290
 291    Actually, we're not picky: FUNCTION can be any kind of object that you're
 292    willing to find in the list returned by `codegen-functions'."))
 293
 294 (export 'temporary-var)
 295 (defgeneric temporary-var (codegen type)
 296   (:documentation
 297    "Return the name of a temporary variable.
 298
 299    The temporary variable will have the given TYPE, and will be marked
 300    in-use.  You should clear the in-use flag explicitly when you've finished
 301    with the variable -- or, better, use `with-temporary-var' to do the
 302    cleanup automatically."))
 303
 304 (export 'codegen-build-function)
 305 (defun codegen-build-function (codegen name type vars insts)
 306   "Build a function and add it to CODEGEN's list.
 307
 308    Returns the function's name."
 309   (codegen-add-function codegen
 310                         (make-function-inst name type
 311                                             (make-block-inst vars insts)))
 312   name)
 313
 314 (export 'codegen-pop-block)
 315 (defgeneric codegen-pop-block (codegen)
 316   (:documentation
 317    "Makes a block (`block-inst') out of the completed code in CODEGEN.")
 318   (:method (codegen)
 319     (multiple-value-bind (vars insts) (codegen-pop codegen)
 320       (make-block-inst vars insts))))
 321
 322 (export 'codegen-pop-function)
 323 (defgeneric codegen-pop-function (codegen name type)
 324   (:documentation
 325    "Makes a function out of the completed code in CODEGEN.
 326
 327    The NAME can be any object you like.  The TYPE should be a function type
 328    object which includes argument names.  The return value is the NAME.")
 329   (:method (codegen name type)
 330     (multiple-value-bind (vars insts) (codegen-pop codegen)
 331       (codegen-build-function codegen name type vars insts))))
 332
 333 (export 'with-temporary-var)
 334 (defmacro with-temporary-var ((codegen var type) &body body)
 335   "Evaluate BODY with VAR bound to a temporary variable name.
 336
 337    During BODY, VAR will be marked in-use; when BODY ends, VAR will be marked
 338    available for re-use."
 339   (multiple-value-bind (doc decls body) (parse-body body :docp nil)
 340     (declare (ignore doc))
 341     `(let ((,var (temporary-var ,codegen ,type)))
 342        ,@decls
 343        (unwind-protect
 344             (progn ,@body)
 345          (setf (var-in-use-p ,var) nil)))))
 346
 347 ;;;--------------------------------------------------------------------------
 348 ;;; Code generation idioms.
 349
 350 (export 'deliver-expr)
 351 (defun deliver-expr (codegen target expr)
 352   "Emit code to deliver the value of EXPR to the TARGET.
 353
 354    The TARGET may be one of the following.
 355
 356      * `:void', indicating that the value is to be discarded.  The expression
 357        will still be evaluated.
 358
 359      * `:void-return', indicating that the value is to be discarded (as for
 360        `:void') and furthermore a `return' from the current function should
 361        be forced after computing the value.
 362
 363      * `:return', indicating that the value is to be returned from the
 364        current function.
 365
 366      * A variable name, indicating that the value is to be stored in the
 367        variable.
 368
 369    In the cases of `:return', `:void' and `:void-return' targets, it is valid
 370    for EXPR to be nil; this signifies that no computation needs to be
 371    performed.  Variable-name targets require an expression."
 372
 373   (case target
 374     (:return (emit-inst codegen (make-return-inst expr)))
 375     (:void (when expr (emit-inst codegen (make-expr-inst expr))))
 376     (:void-return (when expr (emit-inst codegen (make-expr-inst expr)))
 377                   (emit-inst codegen (make-return-inst nil)))
 378     (t (emit-inst codegen (make-set-inst target expr)))))
 379
 380 (export 'convert-stmts)
 381 (defun convert-stmts (codegen target type func)
 382   "Invoke FUNC to deliver a value to a non-`:return' target.
 383
 384    FUNC is a function which accepts a single argument, a non-`:return'
 385    target, and generates statements which deliver a value (see
 386    `deliver-expr') of the specified TYPE to this target.  In general, the
 387    generated code will have the form
 388
 389      setup instructions...
 390      (deliver-expr CODEGEN TARGET (compute value...))
 391      cleanup instructions...
 392
 393    where the cleanup instructions are essential to the proper working of the
 394    generated program.
 395
 396    The `convert-stmts' function will call FUNC to generate code, and arrange
 397    that its value is correctly delivered to TARGET, regardless of what the
 398    TARGET is -- i.e., it lifts the restriction to non-`:return' targets.  It
 399    does this by inventing a new temporary variable."
 400
 401   (case target
 402     (:return (with-temporary-var (codegen var type)
 403                (funcall func var)
 404                (deliver-expr codegen target var)))
 405     (:void-return (funcall func :void)
 406                   (emit-inst codegen (make-return-inst nil)))
 407     (t (funcall func target))))
 408
 409 ;;;----- That's all, folks --------------------------------------------------