9 (define (codegen-add xs si env)
12 (emit "movq ~a(%rbp), %rax" si)
16 (emit "addq $~a, ~a(%rbp)" y si)
18 (codegen-expr y (- si wordsize) env)
19 (emit "addq %rax, ~a(%rbp)" si))))
22 ; use si(%rbp) as the accumulator
23 (emit "movq $0, ~a(%rbp)" si)
26 (define (codegen-binop opcode)
28 (codegen-expr b si env)
29 (emit "movq %rax, ~a(%rbp)" si)
30 (codegen-expr a (- si wordsize) env)
31 (emit "~a ~a(%rbp), %rax" opcode si)))
33 (define codegen-sub (codegen-binop "sub"))
35 (define codegen-mul (codegen-binop "imul"))
37 (define (codegen-not x si env)
38 (codegen-expr x si env)
40 (emit "andq $1, %rax"))
42 (define (codegen-eq a b si env)
43 (codegen-expr a si env)
44 (emit "movq %rax, ~a(%rbp)" si)
45 (codegen-expr b (- si wordsize) env)
46 (emit "subq ~a(%rbp), %rax" si)
48 (emit "andq $1, %rax"))
50 (define (codegen-print x si env)
51 (codegen-expr x si env) ; x should be a static-string, producing a label
53 ; make a copy of string address since %rax and %rdi are clobbered
54 (emit "mov %rax, %rbx")
56 ; get the length of the null terminated string
57 (emit "mov %rax, %rdi")
58 (emit "xor %al, %al") ; set %al to 0
59 (emit "mov $-1, %rcx") ; max search length = max int = -1
60 (emit "cld") ; clear direction flag, search up in memory
61 (emit "repne scasb") ; scan string, %rcx = -strlen - 1 - 1
63 (emit "not %rcx") ; -%rcx = strlen + 1
66 (emit "mov %rcx, %rdx") ; number of bytes
67 (emit "mov %rbx, %rsi") ; addr of string
68 (emit "mov $1, %rax") ; file handle 1 (stdout)
69 (emit "mov $1, %rdi") ; syscall 1 (write)
74 (append (range s (- n 1))
75 (list (+ s (- n 1))))))
79 (define (codegen-let bindings body si env)
80 (let* ((stack-offsets (map (lambda (x) (- si (* x wordsize)))
81 (range 0 (length bindings))))
82 (inner-si (- si (* (length bindings) wordsize)))
83 (names (map car bindings))
84 (exprs (map cadr bindings))
86 ; recursive let bindings: build environment as we go
88 (lambda (env name expr offset)
89 (codegen-expr expr inner-si env)
90 (emit "movq %rax, ~a(%rbp)" offset)
91 (cons (cons name offset) env))
92 env names exprs stack-offsets)))
93 (for-each (lambda (form)
94 (codegen-expr form inner-si inner-env))
97 (define (codegen-var name si env)
98 (when (not (assoc name env))
99 (error #f (format "Variable ~a is not bound" name)))
100 (let ((offset (cdr (assoc name env))))
101 (emit "movq ~a(%rbp), %rax" offset)))
103 (define cur-lambda 0)
104 (define (fresh-lambda)
105 (set! cur-lambda (+ 1 cur-lambda))
106 (format "_lambda~a" (- cur-lambda 1)))
108 ; for now we can only call closures
109 (define (codegen-call closure args si env)
110 (when (not (eq? (ast-type closure) 'closure))
111 (error #f (format "~a is not a closure" closure)))
112 (let* ((captured (caddr closure))
113 (label (cadr closure))
114 (argument-start (length captured)))
116 ; first move the captured variables into param registers
119 (emit "movq ~a(%rbp), ~a"
120 (cdr (assoc e env)) ; offset of the var
122 captured (range 0 (length captured)))
125 ; then codegen the arguments and move them into the next param registers
129 (codegen-expr e si env)
130 ; move result to correct param register
131 (emit "movq %rax, ~a" (param-register i))))
132 args (range argument-start (length args)))
134 (emit "addq $~a, %rsp" si) ; adjust the stack pointer to account all the stuff we put in the env
135 (emit "callq ~a" label)
136 (emit "subq $~a, %rsp" si)))
138 (define (codegen-lambda l)
139 (let* ((label (car l))
143 ; params = what actually gets passed
144 (params (append captured args))
146 (param-registers (map param-register
147 (range 0 (length params))))
148 (stack-offsets (map (lambda (i)
150 (range 1 (length params))))
152 (copy-insts (map (lambda (r o)
153 (format "movq ~a, ~a(%rbp)" r o))
154 param-registers stack-offsets))
156 (env (map cons params stack-offsets)))
158 (display "## lambda body: ")
161 (display "## environment: ")
165 (emit "push %rbp") ; preserve caller's base pointer
166 (emit "movq %rsp, %rbp") ; set up our own base pointer
168 (for-each emit copy-insts)
169 (codegen-expr body (* (- wordsize) (+ 1 (length params))) env)
171 (emit "pop %rbp") ; restore caller's base pointer
175 (define (fresh-label)
176 (set! cur-label (+ 1 cur-label))
177 (format "label~a" (- cur-label 1)))
179 (define (codegen-if cond then else si env)
180 (codegen-expr cond si env)
181 (emit "cmpq $0, %rax")
182 (let ((exit-label (fresh-label))
183 (else-label (fresh-label)))
184 (emit "je ~a" else-label)
185 (codegen-expr then si env)
186 (emit "jmp ~a" exit-label)
187 (emit "~a:" else-label)
188 (codegen-expr else si env)
189 (emit "~a:" exit-label)))
191 (define (codegen-expr e si env)
196 (let ((callee (codegen-expr (car e) si env)))
198 ('+ (codegen-add (cdr e) si env))
199 ('- (codegen-sub (cadr e) (caddr e) si env))
200 ('* (codegen-mul (cadr e) (caddr e) si env))
201 ('! (codegen-not (cadr e) si env))
202 ('= (codegen-eq (cadr e) (caddr e) si env))
203 ('bool->int (codegen-expr (cadr e) si env))
204 ('print (codegen-print (cadr e) si env))
205 (else (codegen-call callee (cdr e) si env)))))
207 ('let (codegen-let (let-bindings e)
212 ('var (codegen-var e si env))
214 ('if (codegen-if (cadr e) (caddr e) (cadddr e) si env))
216 ('bool-literal (emit "movq $~a, %rax" (if e 1 0)))
217 ('int-literal (emit "movq $~a, %rax" e))
219 ('static-string (emit "lea ~a, %rax" (cadr e))) ; move label
221 (else (error #f "don't know how to codegen this"))))
224 (define (fold-map f x) (fold-left append '() (map f x)))
226 (define (free-vars prog)
230 ('builtin '()) ; do nothing
231 ('var (if (memq e bound) '() (list e)))
233 (set! bound (append (lambda-args e) bound))
234 (collect (lambda-body e)))
236 ('app (fold-map collect e))
238 (let ((bind-fvs (fold-map (lambda (a)
239 ((set! bound (cons (car a) bound))
241 (let-bindings cadr)))
242 (body-fvs (fold-map collect (let-body e))))
243 (append bind-fvs body-fvs)))
247 ; ((lambda (x) (+ x 1)) 42) => {lambda0: (x) (+ x 1)}, (@lambda0 42)
248 (define (extract-lambdas program)
250 (define (add-lambda e)
251 (let* ((label (fresh-lambda))
252 (args (lambda-args e))
253 (captured (free-vars e))
254 (body (extract (lambda-body e)))
255 (new-lambda (list label args captured body)))
256 (set! lambdas (cons new-lambda lambdas))
257 `(closure ,label ,captured))) ; todo: should we string->symbol?
260 ('lambda (add-lambda e))
261 ('let `(let ,(map extract (let-bindings e))
262 ,@(map extract (let-body e))))
263 ('app (append (list (extract (car e)))
264 (map extract (cdr e))))
265 (else (ast-traverse extract e))))
266 (let ((transformed (extract program)))
267 (cons lambdas transformed)))
269 (define (extract-strings program)
271 (strings '())) ; assoc list of labels -> string
272 (define (fresh-string)
273 (set! cur-string (+ cur-string 1))
274 (format "string~a" (- cur-string 1)))
278 (let ((label (fresh-string)))
279 (set! strings (cons (cons label e) strings))
280 `(static-string ,label)))
281 (else (ast-traverse extract e))))
282 (let ((transformed (extract program)))
283 (cons strings transformed))))
285 (define (emit-string-data s)
287 (emit "\t.string \"~a\"" (cdr s)))
289 ;; (define (amd64-abi f)
290 ;; ; preserve registers
291 ;; (emit "push %rbp")
292 ;; ;; (emit "push %rbx")
293 ;; ;; (for-each (lambda (i)
294 ;; ;; (emit (string-append
296 ;; ;; (number->string i))))
297 ;; ;; '(12 13 14 15))
299 ;; (emit "movq %rsp, %rbp") ; set up the base pointer
302 ;; ; restore preserved registers
303 ;; ;; (for-each (lambda (i)
304 ;; ;; (emit (string-append
306 ;; ;; (number->string i))))
307 ;; ;; '(15 14 13 12))
308 ;; ;; (emit "pop %rbx")
313 ; 16(%rbp) mem arg 0 prev frame
314 ; -----------------------
315 ; 8(%rbp) return address cur frame
317 ; -8(%rbp) do what you want
318 ; ... do what you want
319 ; 0(%rsp) do what you want
321 (define (param-register n)
329 (else (error #f "need to test out the below"))
330 (else (format "~a(%rsp)" (- n 6)))))
332 (define (codegen program)
333 (let* ((extract-res-0 (extract-strings program))
334 (strings (car extract-res-0))
335 (extract-res-1 (extract-lambdas (cdr extract-res-0)))
336 (lambdas (car extract-res-1))
337 (xform-prog (cdr extract-res-1)))
339 (emit "\t.global _start")
341 ; (emit ".p2align 4,,15") is this needed?
343 (for-each codegen-lambda lambdas)
346 (emit "movq %rsp, %rbp") ; set up the base pointer
347 (codegen-expr xform-prog 0 '())
350 (emit "mov %rax, %rdi")
351 (emit "mov $60, %rax")
356 (for-each emit-string-data strings)))
358 (define (compile-to-binary program output)
359 (when (not (eq? (typecheck program) 'int)) (error #f "not an int"))
360 (let ([tmp-path "/tmp/a.s"])
361 (when (file-exists? tmp-path) (delete-file tmp-path))
362 (with-output-to-file tmp-path
363 (lambda () (codegen program)))
364 (system (format "clang -nostdlib /tmp/a.s -o ~a" output))))