Codegen if statements

[scheme.git] / codegen.scm

diff --git a/codegen.scm b/codegen.scm
index 70a8ca4aa0df75518989d386502765e90e535137..a19b53df53fa239bc700a5d06cccfd86298d7601 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)))
@@ -135,6 +145,23 @@
        (codegen-expr body (* (- wordsize) (length vars)) env)
        ))))                    ; move args and capture vars to stack
 
+(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)
   (case (ast-type e)
     ('builtin e)
@@ -146,6 +173,7 @@
         ('- (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)))))
 
@@ -156,6 +184,8 @@
 
     ('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))
@@ -200,12 +230,11 @@
   (define (extract e)
     (case (ast-type e)
       ('lambda (add-lambda e))
-     ('let `(let
-                   ,(map extract (let-bindings e))
+      ('let `(let ,(map extract (let-bindings e))
               ,@(map extract (let-body 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)))