; Copyright (c) 1993-1999 by Richard Kelsey. See file COPYING.
; This is a backquote-like macro for building nodes.
;
; One goal is to produce code that is as efficient as possible.
;
; (LET-NODES (<spec1> ... <specN>) . <body>)
;
; <spec> ::= (<ident> <real-call>) | ; call node
; (<ident> (<var1> ... <varN>) <call>) | ; lambda node
; (<ident> (<var1> ... <varN> . <last-vars>) <call>) ; lambda node
;
; <var> ::= #f | Ignored variable position
; <ident> | Evaluate <ident> and copy it, rebinding <ident>
; '<ident> | Evaluate <ident> to get the variable
; (<ident> <rep>) (MAKE-VARIABLE <ident> <rep>)
;
; <last-vars> ::= <ident>
;
; <call> ::= <ident> | <real-call>
;
; <real-call> ::= (<primop-id> <exits> . <arg-list>)
;
; <arg-list> ::= (<arg1> ... <argN>) | (<arg1> ... <argN> . <last-args>)
;
; <last-args> ::= <ident>
;
; <arg> ::= 'foo literal node containing the value of foo, no rep
; '(foo rep) " " " " " " " , using rep
; (* foo) reference to foo (which evaluates to a variable)
; (! foo) foo evaluates to a node
; foo short for (! foo) when foo is an atom
; #f put nothing here
; (<primop-id> . <args>) a nested call
;--------------------------------------
;
; Example:
;
; (let-nodes ((c1 (l1 1 cont))
; (l1 ((j type/pointer)) (proc 2 l2 l3 . rest))
; (l2 () ((jump cont (* j)) '(true-value type/boolean)))
; (l3 () ((jump cont (* j)) '(false-value type/boolean))))
; (replace-body node c1))
;
; ==>
;
; (LET ((J (CREATE-VARIABLE 'J TYPE/POINTER)))
; (LET ((C1 (CREATE-CALL-NODE '2 1))
; (C.1225 (CREATE-CALL-NODE (+ '3 (LENGTH REST)) '2))
; (L1 (CREATE-LAMBDA-NODE 'C 'CONT (FLIST1 J '())))
; (C.1224 (CREATE-CALL-NODE '4 0))
; (L2 (CREATE-LAMBDA-NODE 'C 'CONT '()))
; (C.1223 (CREATE-CALL-NODE '4 0))
; (L3 (CREATE-LAMBDA-NODE 'C 'CONT '())))
; (ATTACH 0 C1 L1)
; (ATTACH 1 C1 CONT)
; (ATTACH 0 C.1225 PROC)
; (ATTACH-CALL-ARGS C.1225 (APPEND (LIST L2 L3) REST))
; (ATTACH-BODY L1 C.1225)
; (ATTACH 0 C.1224 (CREATE-PRIMOP-NODE PRIMOP/JUMP))
; (ATTACH-THREE-CALL-ARGS C.1224
; (CREATE-JUMP-MARKER CONT)
; (CREATE-REFERENCE-NODE J)
; (CREATE-LITERAL-NODE TRUE-VALUE TYPE/BOOLEAN))
; (ATTACH-BODY L2 C.1224)
; (ATTACH 0 C.1223 (CREATE-PRIMOP-NODE PRIMOP/JUMP))
; (ATTACH-THREE-CALL-ARGS C.1223
; (CREATE-JUMP-MARKER CONT)
; (CREATE-REFERENCE-NODE J)
; (CREATE-LITERAL-NODE FALSE-VALUE TYPE/BOOLEAN))
; (ATTACH-BODY L3 C.1223)
; (REPLACE-BODY NODE C1)))
;
(define (expand-let-nodes form rename compare)
(destructure (((#f specs . body) form))
(receive (vars nodes code)
(parse-node-specs specs rename compare)
`(,(rename 'let) ,vars
(,(rename 'let) ,nodes
,@code
,@body)))))
(define (test form)
(destructure (((#f specs . body) form))
(receive (vars nodes code)
(parse-node-specs specs identity eq?)
`(let ,vars
(let ,nodes
,@code
,@body)))))
; Parse the specs, returning a list of variable specs, a list of node specs,
; and a list of construction forms. An input spec is either a call or a
; lambda, each is parsed by an appropriate procedure.
(define (parse-node-specs specs r c)
(let loop ((specs (reverse specs)) (vars '()) (nodes '()) (codes '()))
(if (null? specs)
(values vars nodes codes)
(destructure ((((name . spec) . rest) specs))
(cond ((null? (cdr spec))
(receive (node code)
(construct-call name (car spec) r c)
(loop rest vars
`((,name ,node) . ,nodes) (append code codes))))
((= 2 (length spec))
(receive (vs node new-spec call)
(construct-lambda (car spec) (cadr spec) r c)
(loop (if new-spec (cons new-spec rest) rest)
(append vs vars)
`((,name ,node) . ,nodes)
(if call
`((attach-body ,name ,call) . ,codes)
codes))))
(else
(error "illegal spec in LET-NODES ~S" (cons name spec))))))))
; The names of the call-arg relation procedures, indexed by the number of
; arguments handled.
(define call-attach-names
'#(#f
#f
attach-two-call-args
attach-three-call-args
attach-four-call-args
attach-five-call-args))
; Return the node spec and construction forms for a call. This dispatches
; on whether the argument list is proper or not.
;
; <real-call> ::= (<arg0> <exits> <arg1> ... <argN>) |
; (<arg0> <exits> <arg1> ... <argN> . <last-args>))
; ((JUMP l-node value) <arg1> ... <argN>)
; ((JUMP l-node value) <arg1> ... <argN> . <last-args>)
(define (construct-call name specs r c)
(destructure (((proc . args) specs))
(really-construct-call name proc (car args) '() (cdr args) r c)))
(define (construct-nested-call specs r c)
(destructure (((primop-id . args) specs))
(let ((name (r 'call)))
(receive (node code)
(really-construct-call name primop-id 0 '() args r c)
`(,(r 'let) ((,name ,node)) ,@code ,name)))))
(define (really-construct-call name primop-id exits extra args r c)
(receive (arg-count arg-code)
(parse-call-args name extra args r c)
(let ((primop-code (get-primop-code primop-id r)))
(values `(,(r 'make-call-node) ,primop-code ,arg-count ,exits)
arg-code))))
(define (get-primop-code id r)
(cond ((name->enumerand id primop)
=> (lambda (n)
`(,(r 'get-primop) ,n)))
(else
`(,(r 'lookup-primop) ',id))))
; NAME = the call node which gets the arguments
; EXTRA = initial, already expanded arguments
; ARGS = unexpanded arguments
; LAST-ARG = an atom whose value is added to the end of the arguments
; Returns ARG-COUNT-CODE and ARG-CODE
(define (parse-call-args name extra args r c)
(receive (args last-arg)
(decouple-improper-list args)
(let* ((args (append extra (map (lambda (a) (construct-node a r c)) args)))
(count (length args)))
(if (not (null? last-arg))
(values `(,(r '+) ,count (,(r 'length) ,last-arg))
`((,(r 'attach-call-args)
,name
,(if (null? args)
last-arg
`(,(r 'append) (,(r 'list) . ,args) ,last-arg)))))
(values count
(cond ((= count 0)
'())
((and (= count 1) (car args))
`((,(r 'attach) ,name 0 ,(car args))))
((and (< count 6)
(every? identity args))
`((,(r (vector-ref call-attach-names count))
,name
,@args)))
(else
`((,(r 'attach-call-args) ,name (list . ,args))))))))))
; Return proper part of the list and its last-cdr separately.
(define (decouple-improper-list list)
(do ((list list (cdr list))
(res '() (cons (car list) res)))
((atom? list)
(values (reverse! res) list))))
; Dispatch on the type of the SPEC and return the appropriate code.
;
; <arg> ::= 'foo literal node containing the value of foo, no rep
; '(foo rep) literal node containing the value of foo
; (* foo) reference to foo (which evaluates to a variable)
; (! foo) foo evaluates to a node
; name short for (! name) when foo is an atom
(define (construct-node spec r c)
(cond ((atom? spec) spec)
(else
(destructure (((key data) spec))
(case key
((*) `(,(r 'make-reference-node) ,data))
((quote) (if (pair? data)
`(,(r 'make-literal-node) . ,data)
`(,(r 'make-literal-node) ,data type/unknown)))
((!) data)
(else
(construct-nested-call spec r c)))))))
; Parse a lambda spec. This returns a list of variable specs, code to
; construct the lambda node, a spec for the body if necessary, and
; the code needed to put it all together.
(define (construct-lambda vars call r c)
(receive (vars node)
(construct-vars vars r c)
(cond ((null? call)
(values vars node #f #f))
((atom? call)
(values vars node #f call))
(else
(let ((sym (r (generate-symbol 'c))))
(values vars node `(,sym ,call) sym))))))
; Returns the code needed to construct the variables and the code to make
; the lambda node that binds the variables.
;
; <var> ::= #f | Ignored variable position
; <ident> | Evaluate <ident> and copy it, rebinding <ident>
; '<ident> | Evaluate <ident> to get the variable
; (<ident> <rep>) (MAKE-VARIABLE <ident> <rep>)
(define (construct-vars vars r c)
(let loop ((vs vars) (vlist '()) (code '()))
(cond ((atom? vs)
(let ((vars (if (null? vs)
`(,(r 'list) . ,(reverse! vlist))
`(,(r 'append) (,(r 'list) . ,(reverse! vlist))
,vs))))
(values code `(,(r 'make-lambda-node) 'c 'cont ,vars))))
(else
(let ((spec (car vs))
(rest (cdr vs)))
(cond ((null? spec)
(loop rest (cons #f vlist) code))
((atom? spec)
(loop rest (cons spec vlist)
`((,spec (,(r 'copy-variable) ,spec)) . ,code)))
((c (car spec) 'quote)
(loop rest (cons (cadr spec) vlist) code))
(else
(loop rest (cons (car spec) vlist)
`((,(car spec)
(,(r 'make-variable) ',(car spec) ,(cadr spec)))
. ,code)))))))))
;------------------------------------------------------------------------------
; GENSYM utility
(define *generate-symbol-index* 0)
(define (generate-symbol sym)
(let ((i *generate-symbol-index*))
(set! *generate-symbol-index* (+ i 1))
(concatenate-symbol sym "." i)))