+; a closure on the heap looks like:
+; 0-x x+0 x+4 x+12 x+20
+; label #vars var1.... var2.... var3....
+(define (codegen-closure label captured si env)
+ (let* ((heap-offsets (range 4 (length captured))) ; 4, 12, 20, etc.
+ (inner-si (- si (* (length captured) wordsize))))
+ (emit "movl $~a, (heap_start)")
+ (emit "add $4, (heap_start)")
+ (for-each (lambda (var-name new-offset)
+ (emit "movq ~a(%rbp), ~a(heap_start)" ; todo: do we need to copy this?
+ (cdr (assoc var-name env))
+ new-offset)
+ (emit "add $8, (heap_start)")
+ captured
+ stack-offsets)
+)