X-Git-Url: http://git.lukelau.me/?p=scheme.git;a=blobdiff_plain;f=codegen.scm;h=748781d9f4cde883830176a93c651172c8ec81f4;hp=3a01dff778e94f79f675bd26c6f19a39509a9e64;hb=HEAD;hpb=da18430cebcb7b813c9b29841f78d65580c91684

diff --git a/codegen.scm b/codegen.scm
index 3a01dff..748781d 100644
--- a/codegen.scm
+++ b/codegen.scm
@@ -1,118 +1,932 @@
 (load "typecheck.scm")
 (load "ast.scm")
+(load "platform.scm")
+(load "stdlib.scm")
+
+(define target host-os)
 
 (define (emit . s)
   (begin
     (apply printf s)
     (display "\n")))
 
+(define wordsize 8)
+
+(define (stack-type? dls type)
+  (if (adt? dls type)      
+      (> (type-size dls type) wordsize)
+      #f))
+
+(define (adt? data-layouts type) (assoc type data-layouts))
+
+(define (type-size data-layouts type)
+
+  (define (adt-size adt)
+    (let ([sizes
+	   (map (lambda (sum)
+		  (fold-left (lambda (acc x) (+ acc (type-size data-layouts x)))
+			     wordsize ; one word needed to store tag
+			     (cdr sum)))
+		(cdr adt))])
+      (apply max sizes)))
+  
+  (case type
+    ['Int wordsize]
+    [else
+     (let ([adt (assoc type data-layouts)])
+       (if adt
+	   (adt-size adt)
+	   (error #f "unknown size" type)))]))
+
+(define (singletons dls)
+  (flat-map
+   (lambda (sums)
+     (fold-left append '()
+		(filter (lambda (x) (= 1 (length x))) sums)))
+   (map cdr dls)))
+
+(define (singleton? dls x)
+  (memv x (singletons dls)))
+
+					; returns the size of an expression's result in bytes
+(define (expr-size dls e)
+  (if (eqv? (ast-type e) 'stack)
+      (type-size dls (cadr e))
+      wordsize))
+
+(define (on-stack? expr)
+  (case (ast-type expr)
+    ['stack (cadr expr)]
+    [else #f]))
+
+					; does a movsq for something on the stack
+					; src points to the start stack index, but not the top of that index
+					; likewise for dst
+					; | ...  |
+					; +------+ <-- to here
+					; | tag0 |
+					; +------+ <-- src (size = 16)
+					; |  42  |
+					; +------+ <-- start copying from here...
+(define (emit-stack-copy src dst size)
+  (let ([size-to-copy (- size wordsize)])
+    (emit "leaq ~a(%rbp), %rsi" (- src size-to-copy))
+    (emit "leaq ~a(%rbp), %rdi" (- dst size-to-copy))
+    (emit "movq $~a, %rcx" (/ size wordsize))
+    (emit "rep movsq")))
+  
+
+					; an environment consists of adt layouts in scope,
+					; and any bound variables.
+					; bound variables are an assoc list with their stack offset
+(define make-env list)
+(define env-data-layouts car)
+(define env-bindings cadr)
+(define (env-append-bindings env bindings)
+  (make-env (env-data-layouts env)
+	    (append bindings (env-bindings env))))
+
 (define (codegen-add xs si env)
   (define (go ys)
     (if (null? ys)
-      (emit "movq ~a(%rsp), %rax" si)
+	(emit "movq ~a(%rbp), %rax" si)
 	(begin
 	  (let ((y (car ys)))
 	    (if (integer? y)
-		 (emit "addq $~a, ~a(%rsp)" y si)
+		(emit "addq $~a, ~a(%rbp)" y si)
 		(begin
 		  (codegen-expr y (- si wordsize) env)
-		   (emit "addq %rax, ~a(%rsp)" si))))
+		  (emit "addq %rax, ~a(%rbp)" si))))
 	  (go (cdr ys)))))
   (begin
-					; use si(%rsp) as the accumulator
-    (emit "movq $0, ~a(%rsp)" si)
+					; use si(%rbp) as the accumulator
+    (emit "movq $0, ~a(%rbp)" si)
     (go xs)))
 
 (define (codegen-binop opcode)
   (lambda (a b si env)
     (codegen-expr b si env)
-    (emit "movq %rax, ~a(%rsp)" si)
+    (emit "movq %rax, ~a(%rbp)" si)
     (codegen-expr a (- si wordsize) env)
-    (emit "~a ~a(%rsp), %rax" opcode si)))
+    (emit "~a ~a(%rbp), %rax" opcode si)))
 
 (define codegen-sub (codegen-binop "sub"))
+
 (define codegen-mul (codegen-binop "imul"))
 
 (define (codegen-not x si env)
   (codegen-expr x si env)
-  (emit "xorq $-1, %rax")
+  (emit "notq %rax")
   (emit "andq $1, %rax"))
 
-(define (range s n)
-  (if (= 0 n) '()
-      (append (range s (- n 1))
-	      (list (+ s (- n 1))))))
+(define (codegen-eq a b si env)
+  (codegen-expr a si env)
+  (emit "movq %rax, ~a(%rbp)" si)
+  (codegen-expr b (- si wordsize) env)
+  (emit "## ~a = ~b" a b)
+  (emit "cmpq ~a(%rbp), %rax" si)
+  (emit "sete %al"))
 
-(define wordsize 8)
+					; 'write file handle addr-string num-bytes
+
+(define (codegen-print x si env)
+  (codegen-expr x si env) ; x should be a static-string, producing a label
+
+					; make a copy of string address since %rax and %rdi are clobbered
+  (emit "mov %rax, %rbx")
+  
+					; get the length of the null terminated string
+  (emit "mov %rax, %rdi")
+  (emit "xor %al, %al")   ; set %al to 0
+  (emit "mov $-1, %rcx") ; max search length = max int = -1
+  (emit "cld")           ; clear direction flag, search up in memory
+  (emit "repne scasb")   ; scan string, %rcx = -strlen - 1 - 1
+  
+  (emit "not %rcx")      ; -%rcx = strlen + 1
+  (emit "dec %rcx")
+  
+  (emit "movq %rbx, %rsi") ; string addr
+  (emit "movq %rcx, %rdx") ; num bytes
+  (emit "movq $1, %rdi")   ; file handle (stdout)
+  (case target
+    ('darwin (emit "mov $0x2000004, %rax")) ; syscall 4 (write)
+    ('linux  (emit "mov $1, %rax"))) ; syscall 1 (write)
+  (emit "syscall"))
 
 (define (codegen-let bindings body si env)
-  (let* ((stack-offsets (map (lambda (x) (- si (* x wordsize)))
-			     (range 0 (length bindings))))
-	 (inner-si (- si (* (length bindings) wordsize)))
-	 (names (map car bindings))
-	 (exprs (map cadr bindings))
-	 (inner-env (append (map cons names stack-offsets) env)))
-  (for-each (lambda (expr offset)
+
+					; 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))))
+
+  ;; (define (emit-scc scc env)
+  ;;   ; acc is a pair of the env and list of touchups
+  ;;   (define (emit-binding acc binding)
+  ;;     (let ([binding-name (car binding)]
+  ;; 	    [binding-body (cadr binding)]
+
+  ;; 	    [other-bindings (filter
+  ;; 			     (lambda (x) (not (eqv? binding-name x)))
+  ;; 			     scc)]
+  ;; 	    [mutually-recursives
+  ;; 	     (filter
+  ;; 	      (lambda (other-binding)
+  ;; 		(memv other-binding (references binding-body)))
+  ;; 	      other-bindings)]
+
+  ;; 	    [new-touchups (append touchups (cdr acc))])
+
+  ;; 					; TODO: assert that the only mutually recursives are closures
+  ;; 	(for-each
+  ;; 	 (lambda (binding)
+  ;; 	   (when (not (eqv? (ast-type (cadr binding))
+  
+  ;; 	(emit "asdf")
+  ;; 	(cons new-env new-touchups)
+  ;; 	))
+
+  ;;   (fold-left emit-binding (cons env '()) scc))))
+					; assoc map of binding name to size
+
+
+  (define dls (env-data-layouts env))
+  
+  (define stack-sizes
+    (map (lambda (binding) (cons (car binding) (expr-size dls (cadr binding))))
+	 bindings))
+
+					; assoc map of binding name to offset
+  (define stack-offsets
+					; 2  4  2  8  6
+    (let* ([totals                      ; 2  6  8  16 22
+	    (reverse (fold-left (lambda (acc x)
+				  (if (null? acc)
+				      (list x)
+				      (cons (+ x (car acc)) acc)))
+				'()
+				(map cdr stack-sizes)))]
+					; 0  2  6  8  16
+	   [relative-offsets (map - totals (map cdr stack-sizes))]
+	   [absolute-offsets (map (lambda (x) (- si x)) relative-offsets)])
+      (map cons (map car stack-sizes) absolute-offsets)))
+  
+  (let* (
+					; the stack index used when codegening binding body and main body
+					; -> stack ->
+					; [stack-offsets | inner-si]
+	 [inner-si (- si (fold-left + 0 (map cdr stack-sizes)))]
+
+	 [get-offset (lambda (n) (cdr (assoc n stack-offsets)))]
+	 
+	 [inner-env
+	  (fold-left
+	   (lambda (env comps)
+	     (let* ([scc-binding-offsets
+		     (fold-left
+		      (lambda (acc name)
+			(cons (cons name (get-offset name))
+			      acc))
+		      (env-bindings env)
+		      comps)]
+		    [scc-env (make-env (env-data-layouts env) scc-binding-offsets)])
+	       (for-each 
+		(lambda (name)
+		  (let* ([expr (cadr (assoc name bindings))]
+			 [size (expr-size dls expr)])
+		    (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
+				      (make-env
+				       (env-data-layouts scc-env)
+				       (cons (cons name 'self-captive)
+					     (env-bindings scc-env))))
+			(codegen-expr expr inner-si scc-env))
+
+		    (if (on-stack? expr)
+						  ; copy over whatevers on the stack
+			(emit-stack-copy inner-si (get-offset name) size)
+			(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)))
+
+(define (codegen-var e si env)
+  (let* ([stack-type (on-stack? e)]	 
+	 [name (if stack-type (caddr e) e)]
+
+	 [dls (env-data-layouts env)]
+	 
+				    
+	 [stack-offset (assoc name (env-bindings env))])
+
+    (when (and (not stack-offset) (not singleton?))
+      (error #f (format "Variable ~a is not bound" name)))
+
+    (cond
+     [(singleton? dls name)
+      					; singletons don't need to be in the environment
+					; just store the tag
+      (let ([tag (data-sum-tag (env-data-layouts env) name)])
+	(if (on-stack? e)
+	    (emit "movq $~a, ~a(%rbp)" tag si)
+	    (emit "movq $~a, %rax" tag)))]
+     [(on-stack? e) (emit-stack-copy (cdr stack-offset) si (type-size dls stack-type))]
+     [else (emit "movq ~a(%rbp), %rax" (cdr stack-offset))])))
+
+(define cur-lambda 0)
+(define (fresh-lambda)
+  (set! cur-lambda (+ 1 cur-lambda))
+  (format "_lambda~a" (- cur-lambda 1)))
+
+					; a closure on the heap looks like:
+					; 0    8         16        24
+					; addr var1....  var2....  var3....
+
+(define (codegen-closure label captured si env)
+  (let* ((heap-offsets (map (lambda (i) (+ 8 (* 8 i)))
+			    (range 0 (length captured))))) ; 4, 12, 20, etc.
+
+    (emit "## creating closure")
+
+    (emit "movq heap_start@GOTPCREL(%rip), %rbx")
+    
+    (emit "movq (%rbx), %rax")          ; %rax = heap addr of closure
+
+
+					; point heap_start to next space
+    (emit "addq $~a, (%rbx)" (+ 8 (* 8 (length captured))))
+
+    (emit "## storing address to lambda")
+					; store the address to the lambda code
+    (emit "movq ~a@GOTPCREL(%rip), %rbx" label)
+    (emit "movq %rbx, 0(%rax)")
+
+    (emit "## storing captives")
+					; store the captured vars
+    (for-each
+     (lambda (var-name heap-offset)
+       (let ([stack-offset (cdr (assoc var-name (env-bindings 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" stack-offset)
+	       (emit "movq %rbx, ~a(%rax)" heap-offset)))))
+     captured
+     heap-offsets)))
+
+					; for now we can only call closures
+(define (codegen-call f args si env)
+  (codegen-expr f si env)
+
+  (emit "## starting call")
+  
+  (emit "movq %rax, ~a(%rbp)" si) ; store address of closure first on stack
+  
+					; codegen the arguments, store them intermediately
+  (for-each
+   (lambda (e i)
+     (begin
+       (emit "## arg no. ~a" (- i 1))
+       (codegen-expr e (- si (* wordsize i)) env)
+					; store intermediate result on stack
+       (emit "movq %rax, ~a(%rbp)" (- si (* wordsize i)))))
+
+   args (range 1 (length args)))
+
+					; now that we have everything we need on the stack,
+					; move them into the param registers
+
+  (emit "## moving args into place")
+  (for-each
+   (lambda (i) (emit "movq ~a(%rbp), ~a"
+		     (- si (* wordsize i))
+		     (param-register i)))
+   (range 1 (length args)))
+
+					; todo: can this be made more efficient
+  (emit "movq ~a(%rbp), %rax" si)       ; load back pointer to closure
+
+  (emit "## moving captives into place")
+  
+					; move captives into first argument
+  (emit "movq %rax, %rbx")
+  (emit "addq $8, %rbx")
+  (emit "movq %rbx, ~a" (param-register 0))
+
+  (emit "## performing call")
+
+  (emit "addq $~a, %rsp" si) ; adjust the stack pointer to account all the stuff we put in the env
+  (emit "callq *(%rax)")                ; call closure function
+  (emit "subq $~a, %rsp" si))
+
+					; LAMBDAS:
+					; 1st param: pointer to captured args
+					; 2nd param: 1st arg
+					; 3rd param: 2nd arg, etc.
+
+(define (codegen-lambda l)
+  (let* ((label (car l))
+	 (stuff (cdr l))
+	 (dls (car stuff))
+	 (captives (cadr stuff))
+	 (args (caddr stuff))
+	 (body (cadddr stuff))
+					; params = what actually gets passed
+	 (params (append captives args))
+
+	 (stack-offsets (map (lambda (i)
+			       (* (- wordsize) (+ 1 i)))
+			     (range 0 (length params))))
+
+	 [bindings (map cons params stack-offsets)]
+	 [env (make-env dls bindings)])
+    (emit "~a:" label)
+
+    (display "## lambda captives: ")
+    (display captives)
+    (newline)
+    (display "## lambda args: ")
+    (display args)
+    (newline)
+    (display "## lambda body: ")
+    (display body)
+    (newline)
+    
+    (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 (codegen-case switch cases si env)
+  (define dls (env-data-layouts env))
+  (define exit-label (fresh-label))
+
+
+					; checks if equal and returns assoc list of bindings
+  (define (check-equal jne-label type inner-offset x)
+
+					; TODO: tidy this up! comparibles and binds could be merged
+					; (foo a 2 (bar x)) -> ((2 Int 1) ((bar x) A 2))
+					; sum: foo
+    (define (comparibles sum)
+      (let ([product-types (cdr (assoc sum (cdr (assoc type dls))))])
+	(if (null? product-types)
+	    '()
+	    (filter (lambda (x) (not (eqv? 'var (ast-type (car x)))))
+		    (map (lambda (x t i) (list x t i))
+			 (cdr x)
+			 product-types
+			 (range 0 (length product-types)))))))
+    
+    (define (binds sum)
+      (let ([product-types (cdr (assoc sum (cdr (assoc type dls))))])
+	(if (null? product-types)
+	    '()
+	    (filter (lambda (x) (eqv? 'var (ast-type (car x))))
+		    (map (lambda (x i)
+			   (cons x
+				 (- inner-offset
+				    (data-product-offset dls type sum i))))
+			 (cdr x)
+			 (range 0 (length (cdr x))))))))
+	     
+
+    (if (adt? dls type)
+	(let* ([sum (if (list? x) (car x) x)] ; can sometimes be a singleton
+	       [tag (data-sum-tag dls sum)])
+					; the tag is at the top (beginning) of the adt on the stack
+	  (emit "cmpq $~a, ~a(%rbp)" tag inner-offset)
+	  (emit "jne ~a" jne-label)
+
+	  (append (binds sum)
+		  (flat-map
+		   (lambda (cmp) ; cmp = (x type index)
+		     (check-equal jne-label
+				  (cadr cmp)
+				  (- inner-offset (data-product-offset dls type sum (caddr cmp)))
+				  (car cmp)))
+		   (comparibles sum))))
+	(if (eqv? 'var (ast-type x))
+	    (list (cons x inner-offset))
+	    (begin
+	      (emit "cmpq $~a, ~a(%rbp)" x inner-offset)
+	      (emit "jne ~a" jne-label)
+	      '() ))))
+  
+  (define (codegen-adt-match type case)
+    (let* ([match (car case)]
+	   [expr (cadr case)]
+	   [next-section-label (fresh-label)]
+	   [inner-si (- si (type-size dls type))]
+	   [new-env (env-append-bindings env
+		     (check-equal next-section-label type si match))])
+
+
+      (codegen-expr expr inner-si new-env)
+      (emit "jmp ~a" exit-label)
+
+      (emit "~a:" next-section-label)))
+
+  (define (codegen-literal-match case)
+    (let* ([next-section-label (fresh-label)]
+	   [match (car case)]
+	   [val (if (singleton? dls match)
+		    (data-sum-tag dls match)
+		    match)])
+      (emit "cmpq $~a, %rax" val)
+      (emit "jne ~a" next-section-label)
+      (codegen-expr (cadr case) si env)
+      (emit "jmp ~a" exit-label)
+      (emit "~a:" next-section-label)))
+  
+					; generate the switch
+					; (and store it on the stack if not a stack value)
+  (codegen-expr switch si env)
+
+  (if (on-stack? switch)
+					; adt pattern match
+      (for-each (lambda (x) (codegen-adt-match (cadr switch) x)) cases)
+      (for-each codegen-literal-match cases))
+  (emit "~a:" exit-label))
+      
+
+(define (data-tor env e)
+  (if (not (list? e)) #f    
+      (assoc (car e) (flat-map data-tors (env-data-layouts env)))))
+
+					; returns the internal offset in bytes of a product within an ADT
+					; given the constructor layout
+					; constructor-layout: (foo (Int Bool))
+(define (data-product-offset data-layouts type sum index)
+  (let* ([products (cdr (assoc sum (cdr (assoc type data-layouts))))]
+	 [to-traverse (list-head products index)])
+    (fold-left
+     (lambda (acc t) (+ acc (type-size data-layouts t)))
+     wordsize ; skip the tag in the first word
+     to-traverse)))
+
+(define (data-sum-tag data-layouts sum)
+
+  (define (go acc sums)
+    (when (null? sums) (error #f "data-sum-tag no sum for type" sum type))
+    (if (eqv? sum (car sums))
+	acc
+	(go (+ 1 acc) (cdr sums))))
+  (let* ([all-sum-names (flat-map (lambda (x) (map (lambda (y) (cons (car y) (car x))) (cdr x))) data-layouts)]
+	 [type (cdr (assoc sum all-sum-names))]
+	 [type-sums (cdr (assoc type data-layouts))])
+    (go 0 (map car type-sums))))
+
+(define (codegen-data-tor e si env)
+
+  (define dls (env-data-layouts env))
+
+  (define (codegen-destructor tor)
+    (let* ([res (codegen-expr (cadr e) si env)]
+	   [info (cadr tor)]
+	   [type (car info)]
+	   [sum (cadr info)]
+   	   [index (caddr info)]
+   	   [product-type (cadddr info)]
+	   [product-type-size (type-size dls product-type)]
+
+	   [safe-space-offset (- si (type-size dls type))]
+
+	   [inner-offset (- si (data-product-offset dls type sum index))])
+      
+      (when (not (on-stack? (cadr e)))
+	(error #f "trying to destruct something that isn't a stack expression"))      
+      (emit "# deconstructing")
+
+      (if (stack-type? (env-data-layouts env) product-type)
+					; if copying from the stack, need to first copy
+					; to a safe space above to avoid overwriting
+					; the original result on the stack
+					; this is bad. please remove this in the rewrite.
+	  (begin
+	    (emit-stack-copy inner-offset safe-space-offset product-type-size)
+	    (emit-stack-copy safe-space-offset si product-type-size))
+	  (emit "movq ~a(%rbp), %rax" inner-offset))))
+
+  (define (codegen-constructor tor)
+    (let* ([info (cadr tor)]
+	   [type (car info)]
+	   [sum (cadr info)]
+	   [constructor (car e)]
+
+	   [args (cdr e)]
+
+	   [tag (data-sum-tag (env-data-layouts env)
+			      sum)]
+
+	   [inner-si (- si (type-size dls type))]
+
+	   [product-types (cdr (assoc sum (cdr (assoc type dls))))]
+	   
+	   [insert-product
+	    (lambda (expr i product-type)
+	      (let ([dest-offset
+		     (- si (data-product-offset dls type sum i))]
+		    [product-size (type-size dls product-type)])
 		(codegen-expr expr inner-si env)
-	      (emit "movq %rax, ~a(%rsp)" offset))
-	    exprs stack-offsets)
-  (for-each (lambda (form) (codegen-expr form inner-si inner-env)) body)))
+		(if (on-stack? expr)
+		    (emit-stack-copy inner-si dest-offset product-size)
+		    (emit "movq %rax, ~a(%rbp)" dest-offset))))])
 	   
-(define (codegen-var name si env)
-  (let ((offset (cdr (assoc name env))))
-    (emit "movq ~a(%rsp), %rax" offset)))
+					; emit the tag
+      (emit "movq $~a, ~a(%rbp)" tag si)     
+					; generate products
+      (for-each insert-product args (range 0 (length args)) product-types)))
+  
+  (let* ([tor (data-tor env e)]
+	 [constructor (eqv? 'constructor (caddr (cadr tor)))])
+    (if constructor
+	(codegen-constructor tor)
+	(codegen-destructor tor))))
 
 (define (codegen-expr e si env)
-  (cond ((app? e)
+  (emit "# ~a" e)
+  (case (ast-type e)
+    ('closure (codegen-closure (cadr e) (caddr e) si env))
+    ('app
      (case (car e)
        ('+ (codegen-add (cdr e) si env))
        ('- (codegen-sub (cadr e) (caddr e) si env))
        ('* (codegen-mul (cadr e) (caddr e) si env))
        ('! (codegen-not (cadr e) si env))
+       ('= (codegen-eq  (cadr e) (caddr e) si env))
        ('bool->int (codegen-expr (cadr e) si env))
-	   (else (error #f "can't handle anything else yet"))))
-	((let? e) (codegen-let
-		   (let-bindings e)
+       ('print (codegen-print (cadr e) si env))
+       (else
+	(if (data-tor env e)
+	    (codegen-data-tor e si env)
+	    (codegen-call (car e) (cdr e) si env)))))
+
+					; this is a builtin being passed around as a variable
+					; this should have been converted to a closure!
+    ('builtin (error #f "passing about a builtin!" e))
+
+    ('let (codegen-let (let-bindings e)
 		       (let-body e)
 		       si
 		       env))
-	((var? e) (codegen-var e si env))
-	((boolean? e) (emit "movq $~a, %rax" (if e 1 0)))
-	(else (emit "movq $~a, %rax" e))))
-
-(define (codegen program)
-  (emit ".text")
-  (emit ".p2align 4,,15")
-  (emit ".globl _scheme_entry")
-  (emit "_scheme_entry:")
-
-  ; handle incoming call from C
-  (emit "push %rbp")
-  (emit "push %rbx")
-  (for-each (lambda (i)
-	      (emit (string-append
-		     "push %r"
-		     (number->string i))))
-	    '(12 13 14 15))
-
-  ; our code goes here
-  (codegen-expr program 0 '())
-
-  ; restore preserved registers
-  (for-each (lambda (i)
-	      (emit (string-append
-		     "pop %r"
-		     (number->string i))))
-	    '(15 14 13 12))
-  (emit "pop %rbx")
-  (emit "pop %rbp")
-
-  (emit "ret"))
-
-(define (compile-to-binary program)
-  (when (not (eq? (typecheck program) 'int)) (error #f "not an int"))
+
+    ('var (codegen-var e si env))
+
+    ('if (codegen-if (cadr e) (caddr e) (cadddr e) si env))
+    ('case (codegen-case (case-switch e) (case-cases e) si env))
+    
+    ('bool-literal (emit "movq $~a, %rax" (if e 1 0)))
+    ('int-literal (emit "movq $~a, %rax" e))
+    
+    ('static-string (emit "movq ~a@GOTPCREL(%rip), %rax"
+			  (cadr e)))
+
+    ('stack (case (ast-type (caddr e))
+	      ['var (codegen-var e si env)]
+	      [else (codegen-expr (caddr e) si env)]))
+
+    (else (error #f "don't know how to codegen this")))
+  (emit "# done ~a" e))
+
+					; takes in a expr annotated with types and returns a type-less AST
+					; with stack values wrapped
+(define (annotate-stack-values data-layouts ann-e)
+  (define (strip e)
+    (ast-traverse strip (ann-expr e)))
+  (let* ([e (ann-expr ann-e)]
+	 [type (ann-type ann-e)])
+    (if (stack-type? data-layouts type)
+	`(stack ,type
+		,(ast-traverse (lambda (x) (annotate-stack-values data-layouts x)) e))
+	(ast-traverse (lambda (x)
+			(annotate-stack-values data-layouts x))
+		      e))))
+
+(define (free-vars dls prog)
+  (define bound (singletons dls))
+  (define (collect e)
+    (case (ast-type e)
+      ('builtin '()) ; do nothing
+      ('var (if (memv e bound) '() (list e)))
+      ('lambda
+	  (begin
+	    (set! bound (append (lambda-args e) bound))
+	    (collect (lambda-body e))))
+
+      ('app (flat-map collect e))
+      ('if (flat-map collect (cdr e)))
+      ('let
+	  (let ([bind-fvs (flat-map (lambda (a)
+				      (begin
+					(set! bound (cons (car a) bound))
+					(collect (cdr a))))
+				    (let-bindings e))])
+	    (append bind-fvs (flat-map collect (let-body e)))))
+      (else '())))
+  (collect prog))
+
+					; ((lambda (x) (+ x y)) 42) => ((closure lambda1 (y)) 42)
+                                        ;                              [(lambda1 . ((y), (x), (+ x y))]
+					; for builtins, this generates a closure if it is used
+					; outside of an immediate app
+					; but only one closure for each builtin
+
+(define (extract-lambdas dls program)
+  (define lambdas '())
+  (define (add-lambda e)
+    (let* ((label (fresh-lambda))
+	   (args (lambda-args e))
+	   (captured (free-vars dls e))
+	   (body (extract (lambda-body e)))
+	   (new-lambda (cons label (list dls captured args body))))
+      (set! lambdas (cons new-lambda lambdas))
+      `(closure ,label ,captured))) ; todo: should we string->symbol?
+
+  (define (find-builtin-lambda e)
+    (let [(l (assq (builtin-name e) lambdas))]
+      (if l `(closure ,(car l) ,(caadr l)) #f)))
+
+  (define (builtin-name e)
+    (case e
+      ('+ "_add")
+      ('- "_sub")
+      ('* "_mul")
+      ('! "_not")
+      ('= "_eq")
+      ('bool->int "_bool2int")
+      ('print "_print")
+      (else (error #f "don't know this builtin"))))
+  (define (builtin-args e)
+    (case e
+      ('+ '(x y))
+      ('- '(x y))
+      ('* '(x y))
+      ('! '(x))
+      ('= '(x y))
+      ('bool->int '(x))
+      ('print '(x))
+      (else (error #f "don't know this builtin"))))
+
+  (define (add-builtin-lambda e)
+    (let* [(label (builtin-name e))
+	   (captured '())
+	   (args (builtin-args e))
+	   (body `(,e ,@args))
+	   (new-lambda (cons label (list dls captured args body)))]
+      (set! lambdas (cons new-lambda lambdas))
+      `(closure ,label ,captured)))
+  
+  (define (extract e)
+    (case (ast-type e)
+      ('lambda (add-lambda 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
+	     (if (eqv? 'builtin (ast-type (car e)))
+		 (list (car e))
+		 (list (extract (car e))))
+	     (map extract (cdr e))))
+      
+      ('builtin
+       (if (find-builtin-lambda e)
+	   (find-builtin-lambda e)
+	   (add-builtin-lambda e)))
+
+      
+      (else (ast-traverse extract e))))
+  (let ((transformed (extract program)))
+    (cons lambdas transformed)))
+
+(define (extract-strings program)
+  (let ((cur-string 0)
+	(strings '())) ; assoc list of labels -> string
+    (define (fresh-string)
+      (set! cur-string (+ cur-string 1))
+      (format "string~a" (- cur-string 1)))
+    (define (extract e)
+      (case (ast-type e)
+	('string-literal
+	 (let ((label (fresh-string)))
+	   (set! strings (cons (cons label e) strings))
+	   `(static-string ,label)))
+	(else (ast-traverse extract e))))
+    (let ((transformed (extract program)))
+      (cons strings transformed))))
+
+(define (emit-string-data s)
+  (emit "~a:" (car s))
+  (emit "\t.string \"~a\"" (cdr s)))
+
+					; 24(%rbp) mem arg 1
+					; 16(%rbp) mem arg 0          prev frame
+					; -----------------------
+					;  8(%rbp) return address     cur frame
+					;  0(%rbp) prev %rbp
+					; -8(%rbp) do what you want
+					;  ...     do what you want
+					;  0(%rsp) do what you want
+
+(define (param-register n)
+  (case n
+    (0 "%rdi")
+    (1 "%rsi")
+    (2 "%rdx")
+    (3 "%rcx")
+    (4 "%r8")
+    (5 "%r9")
+    (else (error #f "need to test out the below"))
+    (else (format "~a(%rsp)" (- n 6)))))
+
+(define (initialize-heap)
+  (let ((mmap
+	 (case target
+	   ('darwin "0x20000c5")
+	   ('linux "9"))))
+					; allocate some heap memory
+    (emit "mov $~a, %rax" mmap) ; mmap
+    (emit "xor %rdi, %rdi")  ; addr = null
+    (emit "movq $1024, %rsi")   ; length = 1kb
+    (emit "movq $0x3, %rdx") ; prot = read | write = 0x2 | 0x1
+					;    flags = anonymous | private
+    (case target
+      ('darwin (emit "movq $0x1002, %r10")) ; anon = 0x1000, priv = 0x02
+      ('linux (emit "movq $0x22, %r10")))   ; anon = 0x20,   priv = 0x02
+    (emit "movq $-1, %r8") ; fd = -1
+    (emit "xor %r9, %r9") ; offset = 0
+    (emit "syscall")
+					; %rax now contains pointer to the start of the heap
+					; keep track of it
+
+    (emit "movq heap_start@GOTPCREL(%rip), %rsi")
+    (emit "movq %rax, (%rsi)")))
+
+(define (codegen program-without-stdlib)
+  (set! cur-label 0)
+  (set! cur-lambda 0)
+  (let* ([program (append stdlib program-without-stdlib)]
+	 [data-layouts (program-data-layouts program)]
+
+	 [pattern-matched (expand-pattern-matches program)]
+	 [type-annotated (annotate-types pattern-matched)]
+	 [stack-annotated (annotate-stack-values data-layouts
+						 type-annotated)]
+	 
+	 (strings-res (extract-strings stack-annotated))
+	 (strings (car strings-res))
+	 (lambdas-res (extract-lambdas data-layouts (cdr strings-res)))
+	 (lambdas (car lambdas-res))
+	 (xform-prog (cdr lambdas-res)))
+
+					; verify pattern matches are total
+    (verify-cases data-layouts type-annotated)
+
+    (emit "\t.global _start")
+    (emit "\t.text")
+
+    (for-each codegen-lambda lambdas)
+
+    (emit "_start:")
+
+    (initialize-heap)
+
+    (emit "movq %rsp, %rbp")            ; set up the base pointer
+    (codegen-expr xform-prog (- wordsize) (make-env data-layouts '()))
+
+					; exit syscall
+    (emit "mov %rax, %rdi")
+    (case target
+      ('darwin (emit "movq $0x2000001, %rax"))
+      ('linux (emit "mov $60, %rax")))
+    (emit "syscall")
+
+    (emit ".data")
+
+    (emit "heap_start:")
+    (emit "\t.quad 0")
+
+    (for-each emit-string-data strings)))
+
+(define (compile-to-binary program output t)
+  (set! target t)
+  (when (not (eq? (typecheck program) 'Int)) (error #f "not an Int"))
   (let ([tmp-path "/tmp/a.s"])
     (when (file-exists? tmp-path) (delete-file tmp-path))
     (with-output-to-file tmp-path
       (lambda () (codegen program)))
-    (system "clang -fomit-frame-pointer /tmp/a.s rts.c")))
+
+    (case target
+      ('darwin
+       (system "as /tmp/a.s -o /tmp/a.o")
+       (system (format "ld /tmp/a.o -e _start -macosx_version_min 10.14 -static -o ~a" output)))
+      ('linux
+       (system "as /tmp/a.s -o /tmp/a.o")
+       (system (format "ld /tmp/a.o -o ~a" output))))))
+
+; NOTES
+; syscalls in linux and darwin use the following arguments for syscall instruction:
+; %rax = syscall #
+; %rdi = 1st arg
+; %rsi = 2nd arg
+; %rdx = 3rd arg
+; %r10 = 4th arg
+; %r8  = 5th arg
+; %r9  = 6th arg
+
+; on darwin, unix/posix syscalls are offset by 0x2000000 (syscall classes)
+; https://opensource.apple.com/source/xnu/xnu-2782.20.48/bsd/kern/syscalls.master
+; documentation for most syscalls: /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/sys