X-Git-Url: http://git.lukelau.me/?p=scheme.git;a=blobdiff_plain;f=codegen.scm;h=b403939bc2122c2a4c9b5e24980955a2e329402e;hp=d30adc54e61a144097c3b0bb541a5835af8c028a;hb=6684c39cf92a0fa6c21339c6fec8a6e4cf4f463d;hpb=e51b9e423665428c41cddac0642d1e34b18ca1da

diff --git a/codegen.scm b/codegen.scm
index d30adc5..b403939 100644
--- a/codegen.scm
+++ b/codegen.scm
@@ -9,28 +9,29 @@
 (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)
@@ -38,6 +39,36 @@
   (emit "notq %rax")
   (emit "andq $1, %rax"))
 
+(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 "subq ~a(%rbp), %rax" si)
+  (emit "not %rax")
+  (emit "andq $1, %rax"))
+
+(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 "mov %rcx, %rdx") ; number of bytes
+  (emit "mov %rbx, %rsi") ; addr of string
+  (emit "mov $1, %rax") ; file handle 1 (stdout)
+  (emit "mov $1, %rdi") ; syscall 1 (write)
+  (emit "syscall"))
+
 (define (range s n)
   (if (= 0 n) '()
       (append (range s (- n 1))
@@ -51,26 +82,46 @@
 	 (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)
+
+	 ; recursive let bindings: build environment as we go
+	 (inner-env (fold-left
+		     (lambda (env name expr offset)
 		       (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)))
+		       (emit "movq %rax, ~a(%rbp)" offset)
+		       (cons (cons name offset) env))
+		     env names exprs stack-offsets)))
+    (for-each (lambda (form)
+		(codegen-expr form inner-si inner-env))
+	      body)))
 
 (define (codegen-var name si env)
   (when (not (assoc name env))
     (error #f (format "Variable ~a is not bound" name)))
   (let ((offset (cdr (assoc name env))))
-    (emit "movq ~a(%rsp), %rax" offset)))
+    (emit "movq ~a(%rbp), %rax" offset)))
 
 (define cur-lambda 0)
 (define (fresh-lambda)
   (set! cur-lambda (+ 1 cur-lambda))
   (format "_lambda~a" (- cur-lambda 1)))
 
+(define (codegen-closure label captured si env)
+;; (define (codegen-closure label captured si env)
+;;   (let* ((stack-offsets (map (lambda (x) (- si (* x wordsize))))
+;; 			(range 0 (length captured)))
+;; 	 (inner-si (- si (* (length captured) wordsize))))
+;;     (for-each (lambda (var-name new-offset)
+;; 		(emit "movq ~a(%rbp), ~a(%rbp)" ; todo: do we need to copy this?
+;; 		      (cdr (assoc var-name env))
+;; 		      new-offset))
+;; 	      captured
+;; 	      stack-offsets)
+;; )
 					; for now we can only call closures
 (define (codegen-call closure args si env)
+;  (codegen-expr closure si env)
+  (when (not (eq? (ast-type closure) 'closure))
+    (error #f (format "~a is not a closure" closure)))
   (let* ((captured (caddr closure))
 	 (label (cadr closure))
 	 (argument-start (length captured)))
@@ -78,12 +129,11 @@
 					; first move the captured variables into param registers
     (for-each
      (lambda (e i)
-       (emit "movq ~a(%rsp), ~a"
+       (emit "movq ~a(%rbp), ~a"
 	     (cdr (assoc e env)) ; offset of the var
 	     (param-register i)))
      captured (range 0 (length captured)))
 
-    
 					; then codegen the arguments and move them into the next param registers
     (for-each
      (lambda (e i)
@@ -93,30 +143,29 @@
 	 (emit "movq %rax, ~a" (param-register i))))
      args (range argument-start (length args)))
 
-			    		; now call
-    (emit "callq ~a" label)))
-
+    (emit "addq $~a, %rsp" si) ; adjust the stack pointer to account all the stuff we put in the env
+    (emit "callq ~a" label)
+    (emit "subq $~a, %rsp" si)))
 
 (define (codegen-lambda l)
   (let* ((label (car l))
 	 (args (cadr l))
 	 (captured (caddr l))
 	 (body (cadddr l))
-	 ; captured, then args
-	 (vars (append captured args))
+; params = what actually gets passed
+	 (params (append captured args))
 
 	 (param-registers (map param-register
-			     (range 0 (length vars))))
+			       (range 0 (length params))))
 	 (stack-offsets (map (lambda (i)
 			       (* (- wordsize) i))
-			     (range 0 (length vars))))
+			     (range 1 (length params))))
 
 	 (copy-insts (map (lambda (r o)
-			    (format "movq ~a, ~a(%rsp)"
-				    r o))
+			    (format "movq ~a, ~a(%rbp)" r o))
 			  param-registers stack-offsets))
 
-	 (env (map cons vars stack-offsets)))
+	 (env (map cons params stack-offsets)))
     (emit "~a:" label)
     (display "## lambda body: ")
     (display body)
@@ -124,49 +173,80 @@
     (display "## environment: ")
     (display env)
     (newline)
-    (amd64-abi
-     (lambda ()
+
+    (emit "push %rbp") ; preserve caller's base pointer
+    (emit "movq %rsp, %rbp") ; set up our own base pointer
+    
     (for-each emit copy-insts)
-       (codegen-expr body (* (- wordsize) (length vars)) env)
-       ))))			; move args and capture vars to stack
+    (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-expr e si env)
-  (cond ((builtin? e) e)
-	((closure? e) e)
-	
-	((app? e)
+  (case (ast-type e)
+    ('builtin e)
+    ('closure (codegen-closure (cadr e) (caddr e) si env))
+    ('app
      (let ((callee (codegen-expr (car e) si env)))
        (case callee
 	 ('+ (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))
+	 ('print (codegen-print (cadr e) si env))
 	 (else (codegen-call callee (cdr e) si env)))))
 
-	((let? e) (codegen-let
-		   (let-bindings 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))))
+
+    ('var (codegen-var e si env))
+
+    ('if (codegen-if (cadr e) (caddr e) (cadddr e) si env))
+    
+    ('bool-literal (emit "movq $~a, %rax" (if e 1 0)))
+    ('int-literal (emit "movq $~a, %rax" e))
+    
+    ('static-string (emit "lea ~a, %rax" (cadr e))) ; move label
+
+    (else (error #f "don't know how to codegen this"))))
+
 
 (define (fold-map f x) (fold-left append '() (map f x)))
 
 (define (free-vars prog)
   (define bound '())
   (define (collect e)
-    (cond
-     ((builtin? e) '()) ; do nothing
-     ((var? e) (if (memq e bound) '() (list e)))
-     ((lambda? e)
+    (case (ast-type e)
+      ('builtin '()) ; do nothing
+      ('var (if (memq e bound) '() (list e)))
+      ('lambda
 	  (set! bound (append (lambda-args e) bound))
 	(collect (lambda-body e)))
 
-     ((app? e) (fold-map collect e))
-     ((let? e)
+      ('app (fold-map collect e))
+      ('let
 	  (let ((bind-fvs (fold-map (lambda (a)
 				      ((set! bound (cons (car a) bound))
 				       (collect (cdr a))))
@@ -176,9 +256,6 @@
       (else '())))
   (collect prog))
 
-(define (closure? e)
-  (and (list? e) (eqv? (car e) 'closure)))
-
 					; ((lambda (x) (+ x 1)) 42) => {lambda0: (x) (+ x 1)}, (@lambda0 42)
 (define (extract-lambdas program)
   (define lambdas '())
@@ -191,37 +268,58 @@
       (set! lambdas (cons new-lambda lambdas))
       `(closure ,label ,captured))) ; todo: should we string->symbol?
   (define (extract e)
-    (cond
-     ((lambda? e) (add-lambda e))
-     ((let? e) `(let
-		    ,(map extract (let-bindings e))
+    (case (ast-type e)
+      ('lambda (add-lambda e))
+      ('let `(let ,(map extract (let-bindings e))
 	       ,@(map extract (let-body e))))
-     ((app? e) (append (list (extract (car e)))
+      ('app (append (list (extract (car e)))
 		    (map extract (cdr e))))
-     (else e)))
+      (else (ast-traverse extract e))))
   (let ((transformed (extract program)))
     (cons lambdas transformed)))
 
-(define (amd64-abi f)
-					; preserve registers
-  (emit "push %rbp")
-  (emit "push %rbx")
-  (for-each (lambda (i)
-	      (emit (string-append
-		     "push %r"
-		     (number->string i))))
-	    '(12 13 14 15))
-  
-  (f) ; call stuff
-					; 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 (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)))
+
+;; (define (amd64-abi f)
+;; 					; preserve registers
+;;   (emit "push %rbp")
+;;   ;; (emit "push %rbx")
+;;   ;; (for-each (lambda (i)
+;;   ;; 	      (emit (string-append
+;;   ;; 		     "push %r"
+;;   ;; 		     (number->string i))))
+;;   ;; 	    '(12 13 14 15))
+
+;;   (emit "movq %rsp, %rbp")              ; set up the base pointer
+
+;;   (f) ; call stuff
+;; 					; 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"))
 
 					; 24(%rbp) mem arg 1
 					; 16(%rbp) mem arg 0          prev frame
@@ -243,23 +341,49 @@
     (else (error #f "need to test out the below"))
     (else (format "~a(%rsp)" (- n 6)))))
 
-		 
-
 (define (codegen program)
-  (let* ((extract-result (extract-lambdas program))
-	 (lambdas (car extract-result))
-	 (xform-prog (cdr extract-result)))
-    (emit ".text")
-    (emit ".p2align 4,,15")
+  (let* ((extract-res-0 (extract-strings program))
+	 (strings (car extract-res-0))
+	 (extract-res-1 (extract-lambdas (cdr extract-res-0)))
+	 (lambdas (car extract-res-1))
+	 (xform-prog (cdr extract-res-1)))
+
+    (emit "\t.global _start")
+    (emit "\t.text")
+;    (emit ".p2align 4,,15") is this needed?
 
     (for-each codegen-lambda lambdas)
 
-    (emit ".globl _scheme_entry")
-    (emit "_scheme_entry:")
+    (emit "_start:")
+
+    ; allocate some heap memory
+    (emit "mov $9, %rax") ; mmap
+    (emit "xor %rdi, %rdi")  ; addr = null
+    (emit "movq $1024, %rsi")   ; length = 1kb
+    (emit "movq $0x3, %rdx") ; prot = read | write = 0x2 | 0x1
+    (emit "movq $0x22, %r10") ; flags = anonymous | private = 0x20 | 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 %rax, (heap_start)")
+    
+    (emit "movq %rsp, %rbp")            ; set up the base pointer
+    (codegen-expr xform-prog 0 '())
+
+					; exit syscall
+    (emit "mov %rax, %rdi")
+    (emit "mov $60, %rax")
+    (emit "syscall")
+
+    (emit ".data")
 
+    (emit "heap_start:")
+    (emit "\t.quad 0")
 
-    (amd64-abi
-     (lambda () (codegen-expr xform-prog 0 '())))))
+    (for-each emit-string-data strings)))
 
 (define (compile-to-binary program output)
   (when (not (eq? (typecheck program) 'int)) (error #f "not an int"))
@@ -267,4 +391,14 @@
     (when (file-exists? tmp-path) (delete-file tmp-path))
     (with-output-to-file tmp-path
       (lambda () (codegen program)))
-    (system (format "clang -fomit-frame-pointer /tmp/a.s rts.c -o ~a" output))))
+    (system (format "clang -nostdlib /tmp/a.s -o ~a" output))))
+
+; NOTES
+; syscalls in linux 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