Remove C dependency, directly emit _start

[scheme.git] / codegen.scm

diff --git a/codegen.scm b/codegen.scm
index e1b51a60a5ac6c9fcde9f23dd4ca58e9c02f2274..968a428cd2f442bf820ea37c0a01a3e92047e4b5 100644 (file)
--- a/codegen.scm
+++ b/codegen.scm
@@ -38,6 +38,14 @@
   (emit "notq %rax")
   (emit "andq $1, %rax"))
 
+(define (codegen-eq a b si env)
+  (codegen-expr a si env)
+  (emit "movq %rax, ~a(%rsp)" si)
+  (codegen-expr b (- si wordsize) env)
+  (emit "subq ~a(%rsp), %rax" si)
+  (emit "not %rax")
+  (emit "andq $1, %rax"))
+
 (define (range s n)
   (if (= 0 n) '()
       (append (range s (- n 1))
@@ -76,6 +84,8 @@
 
                                        ; for now we can only call closures
 (define (codegen-call closure args 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)))
@@ -135,43 +145,68 @@
        (codegen-expr body (* (- wordsize) (length vars)) env)
        ))))                    ; move args and capture vars to stack
 
-(define (codegen-expr e si env)
-  (cond ((builtin? e) e)
-       ((closure? e) e)
+(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)))
 
-       ((app? e)
+(define (codegen-expr e si env)
+  (case (ast-type e)
+    ('builtin e)
+    ('closure e)
+    ('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))
         (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))
+
+    ('string-literal (emit "movq ~a, %rax" label))
+    ('bool-literal (emit "movq $~a, %rax" (if e 1 0)))
+    ('int-literal (emit "movq $~a, %rax" e))
+
+    (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))))
@@ -181,9 +216,6 @@
       (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 '())
@@ -196,17 +228,18 @@
       (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 (extract-strings program))
+
 (define (amd64-abi f)
                                        ; preserve registers
   (emit "push %rbp")
@@ -248,8 +281,6 @@
     (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))
@@ -259,12 +290,14 @@
 
     (for-each codegen-lambda lambdas)
 
-    (emit ".globl _scheme_entry")
-    (emit "_scheme_entry:")
+    (emit ".globl _start")
+    (emit "_start:")
+    (codegen-expr xform-prog 0 '())
 
-
-    (amd64-abi
-     (lambda () (codegen-expr xform-prog 0 '())))))
+                                       ; exit syscall
+    (emit "mov %rax, %rdi")
+    (emit "mov $60, %rax")
+    (emit "syscall")))
 
 (define (compile-to-binary program output)
   (when (not (eq? (typecheck program) 'int)) (error #f "not an int"))
@@ -272,4 +305,4 @@
     (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))))