Add strings and print primitive

[scheme.git] / codegen.scm

diff --git a/codegen.scm b/codegen.scm
index 968a428cd2f442bf820ea37c0a01a3e92047e4b5..a1a0aa71280e66b510be50964d9c7c37893b1a91 100644 (file)
--- a/codegen.scm
+++ b/codegen.scm
@@ -46,6 +46,25 @@
   (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
+
+                                       ; 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 %rax, %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))
@@ -175,6 +194,7 @@
         ('! (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 (codegen-let (let-bindings e)
@@ -186,10 +206,11 @@
 
     ('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))
     
+    ('static-string (emit "movq $~a, %rax" (cadr e))) ; move label
+
     (else (error #f "don't know how to codegen this"))))
 
 
@@ -238,7 +259,25 @@
   (let ((transformed (extract program)))
     (cons lambdas transformed)))
 
-;(define (extract-strings program))
+(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 (codegen-string-data s)
+  (emit "~a:" (car s))
+  (emit "\t.string \"~a\"" (cdr s)))
 
 (define (amd64-abi f)
                                        ; preserve registers
@@ -282,22 +321,30 @@
     (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.globl _start")
+    (emit "\t.text")
+;    (emit ".p2align 4,,15") is this needed?
 
     (for-each codegen-lambda lambdas)
 
-    (emit ".globl _start")
+
     (emit "_start:")
     (codegen-expr xform-prog 0 '())
 
                                        ; exit syscall
     (emit "mov %rax, %rdi")
     (emit "mov $60, %rax")
-    (emit "syscall")))
+    (emit "syscall")
+
+    (emit "\t.data")
+
+    (for-each codegen-string-data strings)))
 
 (define (compile-to-binary program output)
   (when (not (eq? (typecheck program) 'int)) (error #f "not an int"))