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 ; a closure on the heap looks like:
109 ; 0-x x+0 x+4 x+12 x+20
110 ; label #vars var1.... var2.... var3....
111 (define (codegen-closure label captured si env)
112 (let* ((heap-offsets (range 4 (length captured))) ; 4, 12, 20, etc.
113 (inner-si (- si (* (length captured) wordsize))))
114 (emit "movl $~a, (heap_start)")
115 (emit "add $4, (heap_start)")
116 (for-each (lambda (var-name new-offset)
117 (emit "movq ~a(%rbp), ~a(heap_start)" ; todo: do we need to copy this?
118 (cdr (assoc var-name env))
120 (emit "add $8, (heap_start)")
124 ; for now we can only call closures
125 (define (codegen-call closure args si env)
126 ; (codegen-expr closure si env)
127 (when (not (eq? (ast-type closure) 'closure))
128 (error #f (format "~a is not a closure" closure)))
129 (let* ((captured (caddr closure))
130 (label (cadr closure))
131 (argument-start (length captured)))
133 ; first move the captured variables into param registers
136 (emit "movq ~a(%rbp), ~a"
137 (cdr (assoc e env)) ; offset of the var
139 captured (range 0 (length captured)))
141 ; then codegen the arguments and move them into the next param registers
145 (codegen-expr e si env)
146 ; move result to correct param register
147 (emit "movq %rax, ~a" (param-register i))))
148 args (range argument-start (length args)))
150 (emit "addq $~a, %rsp" si) ; adjust the stack pointer to account all the stuff we put in the env
151 (emit "callq ~a" label)
152 (emit "subq $~a, %rsp" si)))
154 (define (codegen-lambda l)
155 (let* ((label (car l))
159 ; params = what actually gets passed
160 (params (append captured args))
162 (param-registers (map param-register
163 (range 0 (length params))))
164 (stack-offsets (map (lambda (i)
166 (range 1 (length params))))
168 (copy-insts (map (lambda (r o)
169 (format "movq ~a, ~a(%rbp)" r o))
170 param-registers stack-offsets))
172 (env (map cons params stack-offsets)))
174 (display "## lambda body: ")
177 (display "## environment: ")
181 (emit "push %rbp") ; preserve caller's base pointer
182 (emit "movq %rsp, %rbp") ; set up our own base pointer
184 (for-each emit copy-insts)
185 (codegen-expr body (* (- wordsize) (+ 1 (length params))) env)
187 (emit "pop %rbp") ; restore caller's base pointer
191 (define (fresh-label)
192 (set! cur-label (+ 1 cur-label))
193 (format "label~a" (- cur-label 1)))
195 (define (codegen-if cond then else si env)
196 (codegen-expr cond si env)
197 (emit "cmpq $0, %rax")
198 (let ((exit-label (fresh-label))
199 (else-label (fresh-label)))
200 (emit "je ~a" else-label)
201 (codegen-expr then si env)
202 (emit "jmp ~a" exit-label)
203 (emit "~a:" else-label)
204 (codegen-expr else si env)
205 (emit "~a:" exit-label)))
207 (define (codegen-expr e si env)
210 ('closure (codegen-closure (cadr e) (caddr e) si env))
212 (let ((callee (codegen-expr (car e) si env)))
214 ('+ (codegen-add (cdr e) si env))
215 ('- (codegen-sub (cadr e) (caddr e) si env))
216 ('* (codegen-mul (cadr e) (caddr e) si env))
217 ('! (codegen-not (cadr e) si env))
218 ('= (codegen-eq (cadr e) (caddr e) si env))
219 ('bool->int (codegen-expr (cadr e) si env))
220 ('print (codegen-print (cadr e) si env))
221 (else (codegen-call callee (cdr e) si env)))))
223 ('let (codegen-let (let-bindings e)
228 ('var (codegen-var e si env))
230 ('if (codegen-if (cadr e) (caddr e) (cadddr e) si env))
232 ('bool-literal (emit "movq $~a, %rax" (if e 1 0)))
233 ('int-literal (emit "movq $~a, %rax" e))
235 ('static-string (emit "lea ~a, %rax" (cadr e))) ; move label
237 (else (error #f "don't know how to codegen this"))))
240 (define (fold-map f x) (fold-left append '() (map f x)))
242 (define (free-vars prog)
246 ('builtin '()) ; do nothing
247 ('var (if (memq e bound) '() (list e)))
249 (set! bound (append (lambda-args e) bound))
250 (collect (lambda-body e)))
252 ('app (fold-map collect e))
254 (let ((bind-fvs (fold-map (lambda (a)
255 ((set! bound (cons (car a) bound))
257 (let-bindings cadr)))
258 (body-fvs (fold-map collect (let-body e))))
259 (append bind-fvs body-fvs)))
263 ; ((lambda (x) (+ x 1)) 42) => {lambda0: (x) (+ x 1)}, (@lambda0 42)
264 (define (extract-lambdas program)
266 (define (add-lambda e)
267 (let* ((label (fresh-lambda))
268 (args (lambda-args e))
269 (captured (free-vars e))
270 (body (extract (lambda-body e)))
271 (new-lambda (list label args captured body)))
272 (set! lambdas (cons new-lambda lambdas))
273 `(closure ,label ,captured))) ; todo: should we string->symbol?
276 ('lambda (add-lambda e))
277 ('let `(let ,(map extract (let-bindings e))
278 ,@(map extract (let-body e))))
279 ('app (append (list (extract (car e)))
280 (map extract (cdr e))))
281 (else (ast-traverse extract e))))
282 (let ((transformed (extract program)))
283 (cons lambdas transformed)))
285 (define (extract-strings program)
287 (strings '())) ; assoc list of labels -> string
288 (define (fresh-string)
289 (set! cur-string (+ cur-string 1))
290 (format "string~a" (- cur-string 1)))
294 (let ((label (fresh-string)))
295 (set! strings (cons (cons label e) strings))
296 `(static-string ,label)))
297 (else (ast-traverse extract e))))
298 (let ((transformed (extract program)))
299 (cons strings transformed))))
301 (define (emit-string-data s)
303 (emit "\t.string \"~a\"" (cdr s)))
305 ;; (define (amd64-abi f)
306 ;; ; preserve registers
307 ;; (emit "push %rbp")
308 ;; ;; (emit "push %rbx")
309 ;; ;; (for-each (lambda (i)
310 ;; ;; (emit (string-append
312 ;; ;; (number->string i))))
313 ;; ;; '(12 13 14 15))
315 ;; (emit "movq %rsp, %rbp") ; set up the base pointer
318 ;; ; restore preserved registers
319 ;; ;; (for-each (lambda (i)
320 ;; ;; (emit (string-append
322 ;; ;; (number->string i))))
323 ;; ;; '(15 14 13 12))
324 ;; ;; (emit "pop %rbx")
329 ; 16(%rbp) mem arg 0 prev frame
330 ; -----------------------
331 ; 8(%rbp) return address cur frame
333 ; -8(%rbp) do what you want
334 ; ... do what you want
335 ; 0(%rsp) do what you want
337 (define (param-register n)
345 (else (error #f "need to test out the below"))
346 (else (format "~a(%rsp)" (- n 6)))))
348 (define (codegen program)
349 (let* ((extract-res-0 (extract-strings program))
350 (strings (car extract-res-0))
351 (extract-res-1 (extract-lambdas (cdr extract-res-0)))
352 (lambdas (car extract-res-1))
353 (xform-prog (cdr extract-res-1)))
355 (emit "\t.global _start")
357 ; (emit ".p2align 4,,15") is this needed?
359 (for-each codegen-lambda lambdas)
363 ; allocate some heap memory
364 (emit "mov $9, %rax") ; mmap
365 (emit "xor %rdi, %rdi") ; addr = null
366 (emit "movq $1024, %rsi") ; length = 1kb
367 (emit "movq $0x3, %rdx") ; prot = read | write = 0x2 | 0x1
368 (emit "movq $0x22, %r10") ; flags = anonymous | private = 0x20 | 0x02
369 (emit "movq $-1, %r8") ; fd = -1
370 (emit "xor %r9, %r9") ; offset = 0
373 ; %rax now contains pointer to the start of the heap
375 (emit "movq %rax, (heap_start)")
377 (emit "movq %rsp, %rbp") ; set up the base pointer
378 (codegen-expr xform-prog 0 '())
381 (emit "mov %rax, %rdi")
382 (emit "mov $60, %rax")
390 (for-each emit-string-data strings)))
392 (define (compile-to-binary program output)
393 (when (not (eq? (typecheck program) 'int)) (error #f "not an int"))
394 (let ([tmp-path "/tmp/a.s"])
395 (when (file-exists? tmp-path) (delete-file tmp-path))
396 (with-output-to-file tmp-path
397 (lambda () (codegen program)))
398 (system (format "clang -nostdlib /tmp/a.s -o ~a" output))))
401 ; syscalls in linux use the following arguments for syscall instruction: