From: Luke Lau <luke_lau@icloud.com>
Date: Wed, 24 Jul 2019 23:59:30 +0000 (+0100)
Subject: Merge branch 'master' of lukelau.me:/srv/git/scheme
X-Git-Url: https://git.lukelau.me/?p=scheme.git;a=commitdiff_plain;h=5d4aafc1235538212989893f15006acc5d7d8f03;hp=685089345e07943eaab2eec10208ba513ca537b2

Merge branch 'master' of lukelau.me:/srv/git/scheme
---

diff --git a/.gitignore b/.gitignore
index e4e5f6c..02cfc43 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
 *~
+TAGS
diff --git a/codegen.scm b/codegen.scm
index 04a03fa..78ebbad 100644
--- a/codegen.scm
+++ b/codegen.scm
@@ -54,6 +54,9 @@
 (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
@@ -66,12 +69,12 @@
 
   (case target
     ('darwin
-     (emit "movq %rax, %rsi") ; string addr
+     (emit "movq %rbx, %rsi") ; string addr
      (emit "movq %rcx, %rdx") ; num bytes
      (emit "movq $1, %rdi")   ; file handle (stdout)
      (emit "movq $0x2000004, %rax")) ; syscall 4 (write)
     ('linux
-     (emit "mov %rax, %rsi")  ; string addr
+     (emit "mov %rbx, %rsi")  ; string addr
      (emit "mov %rcx, %rdx")  ; num bytes
      (emit "mov $1, %rax")    ; file handle (stdout)
      (emit "mov $1, %rdi"))) ; syscall 1 (write)
@@ -113,8 +116,26 @@
   (set! cur-lambda (+ 1 cur-lambda))
   (format "_lambda~a" (- cur-lambda 1)))
 
+; a closure on the heap looks like:
+; 0-x    x+0   x+4       x+12      x+20
+; label #vars var1....  var2....  var3....
+
+(define (codegen-closure label captured si env)
+  (let* ((heap-offsets (range 4 (length captured))) ; 4, 12, 20, etc.
+	 (inner-si (- si (* (length captured) wordsize))))
+    (emit "movl $~a, (heap_start)")
+    (emit "add $4, (heap_start)")
+    (for-each (lambda (var-name new-offset)
+		(emit "movq ~a(%rbp), ~a(heap_start)" ; todo: do we need to copy this?
+		      (cdr (assoc var-name env))
+		      new-offset)
+		(emit "add $8, (heap_start)")
+	      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))
@@ -129,7 +150,6 @@
 	     (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)
@@ -182,7 +202,7 @@
 (define (codegen-string label)
   (case target
     ('darwin (emit "movq ~a@GOTPCREL(%rip), %rax" label))
-    ('linux  (emit "movq $~a, %rax" label))))
+    ('linux  (emit "lea $~a, %rax" label))))
 
 (define cur-label 0)
 (define (fresh-label)
@@ -204,7 +224,7 @@
 (define (codegen-expr e si env)
   (case (ast-type e)
     ('builtin e)
-    ('closure e)
+    ('closure (codegen-closure (cadr e) (caddr e) si env))
     ('app
      (let ((callee (codegen-expr (car e) si env)))
        (case callee
@@ -295,7 +315,7 @@
     (let ((transformed (extract program)))
       (cons strings transformed))))
 
-(define (codegen-string-data s)
+(define (emit-string-data s)
   (emit "~a:" (car s))
   (emit "\t.string \"~a\"" (cdr s)))
 
@@ -356,6 +376,21 @@
     (for-each codegen-lambda lambdas)
 
     (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 '())
 
@@ -366,9 +401,12 @@
       ('linux (emit "mov $60, %rax")))
     (emit "syscall")
 
-    (emit "\t.data")
+    (emit ".data")
 
-    (for-each codegen-string-data strings)))
+    (emit "heap_start:")
+    (emit "\t.quad 0")
+
+    (for-each emit-string-data strings)))
 
 (define (compile-to-binary program output t)
   (set! target t)
@@ -385,3 +423,13 @@
       ('linux
        (system "as /tmp/a.s -o /tmp/a.o")
        (system (format "ld /tmp/a.o -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
diff --git a/tests.scm b/tests.scm
index 5b1b1bf..89ca852 100644
--- a/tests.scm
+++ b/tests.scm
@@ -48,3 +48,6 @@
 
 (test-prog '((lambda (x y) (+ x y)) 1 2) 3)
 (test-prog '((lambda (x) (+ ((lambda (y) (+ y 1)) 3) x)) 2) 6)
+
+					; passing closures about
+(test-prog '((lambda (z) ((lambda (x) (x 1)) (lambda (y) (+ z y)))) 2) 3)