+ (emit "push %rbp") ; preserve caller's base pointer
+
+ (emit "movq %rsp, %rbp") ; set up our own base pointer
+
+ ; load the captured vars onto the stack
+ (for-each
+ (lambda (i)
+ (begin
+ (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
+ (lambda (i)
+ (begin
+ (emit "movq ~a, %rbx" (param-register (+ 1 i)))
+ (emit "movq %rbx, ~a(%rbp)"
+ (* (- wordsize)
+ (+ 1 (length captives) i)))))
+ (range 0 (length args)))
+
+ (codegen-expr body (* (- wordsize) (+ 1 (length params))) env)
+
+ (emit "pop %rbp") ; restore caller's base pointer
+ (emit "ret")))
+
+(define cur-label 0)
+(define (fresh-label)
+ (set! cur-label (+ 1 cur-label))
+ (format "label~a" (- cur-label 1)))
+
+(define (codegen-if cond then else si env)
+ (codegen-expr cond si env)
+ (emit "cmpq $0, %rax")
+ (let ((exit-label (fresh-label))
+ (else-label (fresh-label)))
+ (emit "je ~a" else-label)
+ (codegen-expr then si env)
+ (emit "jmp ~a" exit-label)
+ (emit "~a:" else-label)
+ (codegen-expr else si env)
+ (emit "~a:" exit-label)))
+
+(define (data-tor env e)
+ (and (list? e)
+ (assoc (car e) (flat-map data-tors (env-adts env)))))
+
+(define (codegen-data-tor e si env)
+
+ (define (codegen-destructor tor)
+ (codegen-expr (cadr e) si env)
+ (let ([index (cadr tor)]
+ [products 2]
+ [to-traverse (list-head products index)]
+ [offset (fold-left
+ (lambda (acc t) (+ acc (type-size t)))
+ wordsize ; skip tag in first word
+ to-traverse)])
+ 3
+ ))
+
+ (let ([tor (data-tor env e)]
+ [constructor (eqv? 'constructor (cadr tor))])
+ (if constructor
+ (codegen-constructor tor)
+ (codegen-destructor tor))))