(define wordsize 8)
(define (codegen-let bindings body si env)
- (let* ((stack-offsets (map (lambda (x) (- si (* x wordsize)))
+
+ ; is this a closure that captures itself?
+ ; e.g. (let ([x 3] [f (closure lambda0 (f x))]) (f))
+ (define (self-captive-closure? name expr)
+ (and (eqv? (ast-type expr) 'closure)
+ (memv name (caddr expr))))
+
+ (let* ((stack-offsets (map (lambda (name x) ; assoc map of binding name to offset
+ (cons name (- si (* x wordsize))))
+ (map car bindings)
(range 0 (length bindings))))
(inner-si (- si (* (length bindings) wordsize)))
- (names (map car bindings))
- (exprs (map cadr bindings))
-
- ; recursive let bindings: build environment as we go
- (inner-env (fold-left
- (lambda (env name expr offset)
- (codegen-expr expr inner-si env)
- (emit "movq %rax, ~a(%rbp)" offset)
- (cons (cons name offset) env))
- env names exprs stack-offsets)))
+
+ (get-offset (lambda (n) (cdr (assoc n stack-offsets))))
+
+ [inner-env
+ (fold-left
+ (lambda (env comps)
+ (let ([scc-env
+ (fold-left
+ (lambda (acc name)
+ (cons (cons name (get-offset name))
+ acc))
+ env
+ comps)])
+ (for-each
+ (lambda (name)
+ (let ([expr (cadr (assoc name bindings))])
+ (emit "## generating ~a with scc-env ~a" name scc-env)
+ (if (self-captive-closure? name expr)
+ ; if self-captive, insert a flag into the environment to let
+ ; codegen-closure realise this!
+ (codegen-expr expr
+ inner-si
+ (cons (cons name 'self-captive)
+ scc-env))
+ (codegen-expr expr inner-si scc-env))
+ (emit "movq %rax, ~a(%rbp)" (get-offset name))))
+ comps)
+ scc-env))
+ env (reverse (sccs (graph bindings))))])
+
(for-each (lambda (form)
(codegen-expr form inner-si inner-env))
body)))
(emit "## storing captives")
; store the captured vars
(for-each
- (lambda (var-name new-offset)
+ (lambda (var-name heap-offset)
+ (let ([stack-offset (cdr (assoc var-name env))])
+ (emit "### captive ~a" var-name)
+ (if (eqv? stack-offset 'self-captive)
+ ; captive refers to this closure:
+ ; move heap addr of this closure to stack!
+ (emit "movq %rax, ~a(%rax)" heap-offset)
(begin
- (emit "movq ~a(%rbp), %rbx" (cdr (assoc var-name env)))
- (emit "movq %rbx, ~a(%rax)" new-offset)))
+ (emit "movq ~a(%rbp), %rbx" stack-offset)
+ (emit "movq %rbx, ~a(%rax)" heap-offset)))))
captured
heap-offsets)))
(define (codegen-lambda l)
(let* ((label (car l))
(stuff (cdr l))
- (captured (car stuff))
+ (captives (car stuff))
(args (cadr stuff))
(body (caddr stuff))
; params = what actually gets passed
- (params (append captured args))
+ (params (append captives args))
(stack-offsets (map (lambda (i)
- (* (- wordsize) i))
+ (* (- wordsize) (+ 1 i)))
(range 0 (length params))))
(env (map cons params stack-offsets)))
(emit "~a:" label)
(display "## lambda captives: ")
- (display captured)
+ (display captives)
(newline)
(display "## lambda args: ")
(display args)
(emit "push %rbp") ; preserve caller's base pointer
(emit "movq %rsp, %rbp") ; set up our own base pointer
- (emit "subq $8, %rbp")
; load the captured vars onto the stack
(for-each
(lambda (i)
(begin
- (emit "movq ~a(~a), %rbx" i (param-register 0))
- (emit "movq %rbx, ~a(%rbp)" (* (- wordsize) i))))
- (range 0 (length captured)))
+ (emit "# loading captive ~a" (list-ref captives i))
+ (emit "movq ~a(~a), %rbx" (* wordsize i) (param-register 0))
+ (emit "movq %rbx, ~a(%rbp)" (* (- wordsize) (+ 1 i)))))
+ (range 0 (length captives)))
; load the args onto the stack
(for-each
(emit "movq ~a, %rbx" (param-register (+ 1 i)))
(emit "movq %rbx, ~a(%rbp)"
(* (- wordsize)
- (+ (length captured) i)))))
+ (+ 1 (length captives) i)))))
(range 0 (length args)))
(codegen-expr body (* (- wordsize) (+ 1 (length params))) env)
(emit "~a:" exit-label)))
(define (codegen-expr e si env)
+ (emit "# ~a" e)
(case (ast-type e)
('closure (codegen-closure (cadr e) (caddr e) si env))
('app
(define (collect e)
(case (ast-type e)
('builtin '()) ; do nothing
- ('var (if (memq e bound) '() (list e)))
+ ('var (if (memv e bound) '() (list e)))
('lambda
+ (begin
(set! bound (append (lambda-args e) bound))
- (collect (lambda-body e)))
+ (collect (lambda-body e))))
('app (fold-map collect e))
+ ('if (fold-map collect (cdr e)))
('let
- (let ((bind-fvs (fold-map (lambda (a)
- ((set! bound (cons (car a) bound))
+ (let ([bind-fvs (fold-map (lambda (a)
+ (begin
+ (set! bound (cons (car a) bound))
(collect (cdr a))))
- (let-bindings cadr)))
- (body-fvs (fold-map collect (let-body e))))
- (append bind-fvs body-fvs)))
+ (let-bindings e))])
+ (append bind-fvs (fold-map collect (let-body e)))))
(else '())))
(collect prog))
(define (extract e)
(case (ast-type e)
('lambda (add-lambda e))
- ('let `(let ,(map extract (let-bindings e))
+ ('let `(let ,(map (lambda (b) `(,(car b) ,@(extract (cdr b)))) (let-bindings e))
,@(map extract (let-body e))))
('app (append
; if a builtin is used as a function, don't generate lambda
(emit "movq %rax, (%rsi)")))
(define (codegen program)
+ (set! cur-label 0)
+ (set! cur-lambda 0)
(let* ((extract-res-0 (extract-strings program))
(strings (car extract-res-0))
(extract-res-1 (extract-lambdas (cdr extract-res-0)))
(initialize-heap)
(emit "movq %rsp, %rbp") ; set up the base pointer
- (codegen-expr xform-prog 0 '())
+
+ (codegen-expr xform-prog wordsize '())
; exit syscall
(emit "mov %rax, %rdi")