From 5899f8f02a90a3ba03f7799bcaf87fbb5d2d63f2 Mon Sep 17 00:00:00 2001
From: Jan Tuomi <jan@jantuomi.fi>
Date: Tue, 4 Mar 2025 22:55:32 +0200
Subject: Add %if and %if-else macros, refactor, add indirection levels

---
 atk16_schasm/core.scm | 383 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 383 insertions(+)
 create mode 100644 atk16_schasm/core.scm

(limited to 'atk16_schasm/core.scm')

diff --git a/atk16_schasm/core.scm b/atk16_schasm/core.scm
new file mode 100644
index 0000000..4b33648
--- /dev/null
+++ b/atk16_schasm/core.scm
@@ -0,0 +1,383 @@
+(import (chicken base)
+	(chicken bitwise)
+	(chicken format)
+	(chicken io))
+
+;; Utils
+
+(define-syntax @
+  (syntax-rules ()
+    ((_ fn-body expr ...)
+     (lambda (x) (fn-body expr ... x)))))
+
+(define (type-of pair)
+  (if (pair? pair) (car pair) (error "not a pair" pair)))
+(define (val-of pair)
+  (if (pair? pair) (cdr pair) (error "not a pair" pair)))
+
+(define (assocar k alist)
+  (let ((v (assoc k alist)))
+    (and v (car v))))
+(define (assocdr k alist)
+  (let ((v (assoc k alist)))
+    (and v (cdr v))))
+
+(define (string->ascii-list s)
+  (let* ((len (string-length s))
+         (dummy (cons #f '()))
+         (tail dummy))
+    (do ((i 0 (+ i 1)))
+        ((= i len))
+      (set-cdr! tail (cons (char->integer (string-ref s i)) '()))
+      (set! tail (cdr tail)))
+    (cdr dummy)))
+
+;; State
+
+(define *buffer* (make-vector (* 2 (expt 2 16)) #f))
+(define *cursor* 0)
+(define *labels* '())
+
+;; Buffer write and eval
+
+(define (write-image-to filepath)
+  (eval-*buffer*)
+
+  (let ((port (open-output-file filepath)))
+    (do ((i 0 (+ i 1)))
+        ((= i (vector-length *buffer*)))
+      (write-byte (vector-ref *buffer* i) port))
+    (close-output-port port)))
+
+(define (eval-*buffer*)
+  (let loop ((i 0))
+    (if (< i (vector-length *buffer*))
+	(let* ((elem   (vector-ref *buffer* i))
+	       (evaled (eval-*buffer*-elem elem)))
+	  (vector-set! *buffer* i evaled)
+	  (loop (+ i 1))))))
+
+(define (eval-*buffer*-elem elem)
+  (cond
+   ((number? elem) elem)
+   ((eq? #f elem)  0)
+   ((eq? 'label (type-of elem))
+    (let* ((elem-val (val-of elem))
+	   (qualif   (car elem-val))
+	   (label    (cadr elem-val))
+	   (addr     (or (assocdr label *labels*)
+			 (error "deferred label ref was never defined" label))))
+      (cond
+       ((eq? 'hi qualif)  (arithmetic-shift addr -8))
+       ((eq? 'lo qualif)  (bitwise-and #xFF addr))
+       ((eq? 'rel qualif) (- addr (caddr elem-val)))
+       (else            (error "invalid qualifier in elem" elem)))))
+   (else (error "invalid elem" elem))))
+
+;; Encode and emit
+
+(define (encode-byte . chunks)
+  (let ((total-bits (apply + (map car chunks))))
+    (unless (= total-bits 8)
+      (error "emit: total bits in chunks must equal 8, got" total-bits)))
+
+  (let loop ((chs chunks) (acc 0))
+    (if (null? chs)
+        acc
+        (let* ((chunk (car chs))
+               (n     (car chunk))
+               (val   (cdr chunk)))
+
+          (when (>= val (expt 2 n))
+            (error "emit: value" val "does not fit in" n "bits"))
+
+          ;; shift acc left by n bits and combine with val
+          (loop (cdr chs)
+                (bitwise-ior (arithmetic-shift acc n) val))))))
+
+(define (emit-byte-chunks . chunks)
+  (unless (eq? (vector-ref *buffer* *cursor*) #f)
+    (error "overwriting already written memory at" *cursor*))
+
+  (define byte (apply encode-byte chunks))
+
+  (vector-set! *buffer* *cursor* byte)
+  (set! *cursor* (+ *cursor* 1)))
+
+(define (emit-byte b)
+  (unless (and (>= b 0)
+	       (<  b (expt 2 8)))
+    (error "value out of bounds" byte))
+
+  (emit-byte-chunks `(8 . ,b)))
+
+(define (emit-word w)
+  (unless (and (>= w 0)
+	       (<  w (expt 2 16)))
+    (error "value out of bounds" w))
+
+  ;; emit a word as two bytes
+  (emit-byte-chunks `(8 . ,(arithmetic-shift w -8)))
+  (emit-byte-chunks `(8 . ,(bitwise-and #xFF w))))
+
+(define (emit-deferred-sexpr sexpr)
+  (unless (pair? sexpr)
+    (error "not a pair" sexpr))
+  (vector-set! *buffer* *cursor* sexpr)
+  (set! *cursor* (+ *cursor* 1)))
+
+;; Directives
+
+(define (def-label sym . exprs)
+  (when (assoc sym *labels*)
+    (error "label already defined" sym))
+
+  (set! *labels* (cons (cons sym *cursor*) *labels*))
+  ;; don't do anything with exprs, it's there for allowing
+  ;; a nice appearance for labeled blocks
+  )
+
+(define (at-addr addr)
+  (unless (and (number? addr)
+	       (>= addr 0)
+	       (< addr (expt 2 16)))
+    (error "invalid addr" addr))
+
+  (set! *cursor* addr))
+
+;; Value constructors and references
+
+(define (label sym)
+  (cons 'label sym))
+
+(define (reg n)
+  (cond
+   ((or (< n 0) (>= n 16)) (error "invalid arg to reg" n))
+   (else (cons 'reg n))))
+
+(define R0  (reg 0))
+(define R1  (reg 1))
+(define R2  (reg 2))
+(define R3  (reg 3))
+(define R4  (reg 4))
+(define R5  (reg 5))
+(define R6  (reg 6))
+(define R7  (reg 7))
+(define R8  (reg 8))
+(define R9  (reg 9))
+(define R10 (reg 10))
+(define R11 (reg 11))
+(define R12 (reg 12))
+(define R13 (reg 13))
+(define R14 (reg 14))
+(define R15 (reg 15))
+
+(define FL (reg 13))
+(define PC (reg 14))
+(define SP (reg 15))
+
+(define (imm n)
+  (cons 'imm n))
+
+(define (i16 n)
+  (unless (and (<  n (expt 2 15))
+	       (>= n (- (expt 2 15))))
+    (error "n does not fit in bounds" n))
+  (imm (modulo n (expt 2 16))))
+
+(define (u16 n)
+  (unless (and (<  n (expt 2 16))
+	       (>= n 0))
+    (error "n does not fit in bounds" n))
+  (imm n))
+
+(define (i8 n)
+  (unless (and (<  n (expt 2 7))
+	       (>= n (- (expt 2 7))))
+    (error "n does not fit in bounds" n))
+  (imm (modulo n (expt 2 16))))
+
+(define (u8 n)
+  (unless (and (<  n (expt 2 8))
+	       (>= n 0))
+    (error "n does not fit in bounds" n))
+  (imm n))
+
+(define (alu-op n)
+  (unless (and (>= n 0)
+	       (<  n 8))
+    (error "invalid arg to alu-op" n))
+  (cons 'alu-op n))
+
+(define alu-plus  (alu-op 0))
+(define alu-minus (alu-op 1))
+(define alu-and   (alu-op 2))
+(define alu-or    (alu-op 3))
+(define alu-xor   (alu-op 4))
+(define alu-shl   (alu-op 5))
+(define alu-shr   (alu-op 6))
+(define alu-sar   (alu-op 7))
+
+(define (flag n)
+  (unless (and (>= n 0)
+	       (<  n 4))
+    (error "invalid arg to flag" n))
+  (cons 'flag n))
+
+(define flag-carry    (flag 0))
+(define flag-overflow (flag 1))
+(define flag-zero     (flag 2))
+(define flag-sign     (flag 3))
+
+;; Instructions
+
+(define (hlt)
+  ;; just full zeros
+  (emit-word 0))
+
+(define (alu op lhs rhs)
+  (unless (eq? 'alu-op (type-of op)) (error "invalid op" op))
+  (unless (eq? 'reg (type-of lhs)) (error "invalid lhs" lhs))
+
+  (define rhs-type (type-of rhs))
+  (define m-mode
+    (cond ((eq? 'reg rhs-type)   0)
+	  ((eq? 'imm rhs-type)   1)
+	  ((eq? 'label rhs-type) 1)
+	  (else (error "invalid rhs" rhs))))
+
+  (if (= m-mode 0)
+      ;; reg mode
+      (begin
+	(emit-byte-chunks `(4 . 1)
+			  `(3 . ,(val-of op))
+			  `(1 . ,m-mode))
+	(emit-byte-chunks `(4 . ,(val-of lhs))
+	                  `(4 . ,(val-of rhs))))
+
+      ;; immediate mode
+      (begin
+	(emit-byte-chunks `(4 . 1)
+			  `(3 . ,(val-of op))
+			  `(1 . ,m-mode))
+	(emit-byte-chunks `(4 . ,(val-of lhs))
+			  `(4 . 0))
+
+	(if (eq? 'label rhs-type)
+	    ;; if label, emit a label reference
+	    (begin (emit-deferred-sexpr `(label . (hi ,(val-of rhs))))
+		   (emit-deferred-sexpr `(label . (lo ,(val-of rhs)))))
+	    ;; otherwise, emit the value
+	    (emit-word (val-of rhs))))))
+
+(define (add lhs rhs) (alu (alu-op 0) lhs rhs))
+(define (sub lhs rhs) (alu (alu-op 1) lhs rhs))
+(define (and lhs rhs) (alu (alu-op 2) lhs rhs))
+(define (or  lhs rhs) (alu (alu-op 3) lhs rhs))
+(define (xor lhs rhs) (alu (alu-op 4) lhs rhs))
+(define (shl lhs rhs) (alu (alu-op 5) lhs rhs))
+(define (shr lhs rhs) (alu (alu-op 6) lhs rhs))
+(define (sar lhs rhs) (alu (alu-op 7) lhs rhs))
+
+(define (ld lhs rhs #!key (indirect 0) (pop #f))
+  (unless (eq? 'reg (type-of lhs)) (error "invalid lhs" lhs))
+
+  (define p-mode (if pop 1 0))
+
+  (define rhs-type (type-of rhs))
+  (define m-mode
+    (cond ((eq? 'reg rhs-type)   0)
+	  ((eq? 'imm rhs-type)   1)
+	  ((eq? 'label rhs-type) 1)
+	  (else (error "invalid rhs" rhs))))
+
+  (if (= m-mode 0)
+      ;; reg mode
+      (begin
+	(emit-byte-chunks `(4 . 2)
+			  `(2 . ,indirect)
+			  `(1 . ,p-mode)
+			  `(1 . ,m-mode))
+	(emit-byte-chunks `(4 . ,(val-of lhs))
+			  `(4 . ,(val-of rhs))))
+
+      ;; immediate mode
+      (begin
+	(emit-byte-chunks `(4 . 2)
+			  `(2 . ,indirect)
+			  `(1 . ,p-mode)
+			  `(1 . ,m-mode))
+	(emit-byte-chunks `(4 . ,(val-of lhs))
+			  `(4 . 0))
+
+	(if (eq? 'label rhs-type)
+	    ;; if label, emit a label reference
+	    (begin (emit-deferred-sexpr `(label . (hi ,(val-of rhs))))
+		   (emit-deferred-sexpr `(label . (lo ,(val-of rhs)))))
+	    ;; otherwise, emit the value
+	    (emit-word (val-of rhs))))))
+
+(define (st lhs rhs #!key (indirect 0) (push #f))
+  (unless (eq? 'reg (type-of lhs)) (error "invalid lhs" lhs))
+
+  (define p-mode (if push 1 0))
+
+  (define rhs-type (type-of rhs))
+  (define m-mode
+    (cond ((eq? 'reg rhs-type)   0)
+	  ((eq? 'imm rhs-type)   1)
+	  ((eq? 'label rhs-type) 1)
+	  (else (error "invalid rhs" rhs))))
+
+  (if (= m-mode 0)
+      ;; reg mode
+      (begin
+	(emit-byte-chunks `(4 . 4)
+			  `(2 . ,indirect)
+			  `(1 . ,p-mode)
+			  `(1 . ,m-mode))
+	(emit-byte-chunks `(4 . ,(val-of lhs))
+			  `(4 . ,(val-of rhs))))
+
+      ;; immediate mode
+      (begin
+	(emit-byte-chunks `(4 . 4)
+			  `(2 . ,indirect)
+			  `(1 . ,p-mode)
+			  `(1 . ,m-mode))
+	(emit-byte-chunks `(4 . ,(val-of lhs))
+			  `(4 . 0))
+
+	(if (eq? 'label rhs-type)
+	    ;; if label, emit a label reference
+	    (begin (emit-deferred-sexpr `(label . (hi ,(val-of rhs))))
+		   (emit-deferred-sexpr `(label . (lo ,(val-of rhs)))))
+	    ;; otherwise, emit the value
+	    (emit-word (val-of rhs))))))
+
+(define (br flag offset #!key (asserted #t))
+  (unless (eq? 'flag (type-of flag)) (error "invalid flag selector" flag))
+
+  (define set
+    (cond ((eq? #t asserted) 1)
+	  ((eq? #f asserted) 0)
+	  (else (error "invalid asserted bool" asserted))))
+
+  (define offset-type (type-of offset))
+  (cond
+   ((eq? 'imm offset-type)
+    (let* ((imm (val-of offset)))
+      (unless (< imm (expt 2 8)) (error "offset too large" imm))
+
+      (emit-byte-chunks `(4 . 5)
+			`(2 . ,(val-of flag))
+			`(1 . 0)
+			`(1 . ,set))
+      (emit `(8 . ,imm))))
+   ((eq? 'label offset-type)
+    (emit-byte-chunks `(4 . 5)
+		      `(2 . ,(val-of flag))
+		      `(1 . 0)
+		      `(1 . ,set))
+    (emit-deferred-sexpr `(label . (rel ,(val-of offset) ,(+ *cursor* 1)))))
+   (else (error "invalid offset" offset))))
-- 
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