1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
|
(import (chicken base)
(chicken bitwise)
(chicken format)
(chicken io))
(define *buffer* (make-vector (expt 2 16) #f))
(define *cursor* 0)
(define *labels* '())
;; Meta
(define (write-image-to filepath)
(let ((port (open-output-file filepath)))
(do ((i 0 (+ i 1)))
((= i (vector-length *buffer*)))
(let* ((word (or (vector-ref *buffer* i) 0))
(high (arithmetic-shift word -8)) ; high byte: shift right by 8 bits
(low (bitwise-and word #xFF))) ; low byte: mask with 0xFF
(write-byte high port)
(write-byte low port)))
(close-output-port port)))
;; Directives
(define (def-label sym . exprs)
(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)
(assocdr sym *labels*))
(define (reg n)
(cond
((or (< n 0) (>= n 16)) (error "invalid arg to reg" n))
(else `(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)
`(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))
`(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))
`(flag ,n))
(define flag-carry (flag 0))
(define flag-overflow (flag 1))
(define flag-zero (flag 2))
(define flag-sign (flag 3))
;; Encode and emit
(define (emit . chunks)
(unless (eq? (vector-ref *buffer* *cursor*) #f)
(error "overwriting already written memory at" *cursor*))
(define word
(if (and (= (length chunks) 1)
(number? (car chunks)))
;; single argument
(car chunks)
;; multiple (bits . value) pairs
(apply encode chunks)))
(vector-set! *buffer* *cursor* word)
(set! *cursor* (+ *cursor* 1)))
(define (encode . chunks)
(let ((total-bits (apply + (map car chunks))))
(unless (= total-bits 16)
(error "emit: total bits in chunks must equal 16, 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))))))
;; Instructions
(define (hlt)
;; just full zeros
(emit 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 mode
(cond ((eq? 'reg (type-of rhs)) 0)
((eq? 'imm (type-of rhs)) 1)
(else (error "invalid rhs" rhs))))
(if (= mode 0)
;; reg mode
(emit `(4 . 1) ; opcode = 1
`(3 . ,(cadr op)) ; alu op
`(1 . ,mode) ; reg/imm mode
`(4 . ,(cadr lhs)) ; lhs
`(4 . ,(cadr rhs))) ; rhs
;; immediate mode
(begin
(emit `(4 . 1) ; opcode = 1
`(3 . ,(cadr op)) ; alu op
`(1 . ,mode) ; reg/imm mode
`(4 . ,(cadr lhs)) ; lhs
`(4 . 0)) ; unused
(emit `(16 . ,(cadr rhs)))) ; 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 #f) (pop #f))
(unless (eq? 'reg (type-of lhs)) (error "invalid lhs" lhs))
(define d-mode (if indirect 1 0))
(define p-mode (if pop 1 0))
(define m-mode
(cond ((eq? 'reg (type-of rhs)) 0)
((eq? 'imm (type-of rhs)) 1)
(else (error "invalid rhs" rhs))))
(if (= m-mode 0)
;; reg mode
(emit `(4 . 2) ; opcode = 2
`(1 . ,d-mode) ; indirect mode
`(1 . ,p-mode) ; pop mode
`(1 . 0) ; unused
`(1 . ,m-mode) ; reg/imm mode
`(4 . ,(cadr lhs)) ; lhs
`(4 . ,(cadr rhs))) ; rhs
;; immediate mode
(begin
(emit `(4 . 2) ; opcode = 2
`(1 . ,d-mode) ; indirect mode
`(1 . ,p-mode) ; pop mode
`(1 . 0) ; unused
`(1 . ,m-mode) ; reg/imm mode
`(4 . ,(cadr lhs)) ; lhs
`(4 . 0)) ; unused
(emit `(16 . ,(cadr rhs)))) ; rhs
))
(define (mov lhs rhs)
(unless (eq? 'reg (type-of lhs)) (error "invalid lhs" lhs))
(unless (eq? 'reg (type-of rhs)) (error "invalid rhs" rhs))
(emit `(4 . 3) ; opcode = 3
`(4 . 0) ; unused
`(4 . ,(cadr lhs)) ; lhs
`(4 . ,(cadr rhs)))) ; rhs
(define (st lhs rhs #!key (indirect #f) (push #f))
(unless (eq? 'reg (type-of lhs)) (error "invalid lhs" lhs))
(define d-mode (if indirect 1 0))
(define p-mode (if push 1 0))
(define m-mode
(cond ((eq? 'reg (type-of rhs)) 0)
((eq? 'imm (type-of rhs)) 1)
(else (error "invalid rhs" rhs))))
(if (= m-mode 0)
;; reg mode
(emit `(4 . 4) ; opcode = 4
`(1 . ,d-mode) ; indirect mode
`(1 . ,p-mode) ; pop mode
`(1 . 0) ; unused
`(1 . ,m-mode) ; reg/imm mode
`(4 . ,(cadr lhs)) ; lhs
`(4 . ,(cadr rhs))) ; rhs
;; immediate mode
(begin
(emit `(4 . 4) ; opcode = 4
`(1 . ,d-mode) ; indirect mode
`(1 . ,p-mode) ; pop mode
`(1 . 0) ; unused
`(1 . ,m-mode) ; reg/imm mode
`(4 . ,(cadr lhs)) ; lhs
`(4 . 0)) ; unused
(emit `(16 . ,(cadr rhs)))) ; 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))))
(unless (eq? 'imm (type-of offset)) (error "invalid offset" offset))
(define imm (cadr offset))
(unless (< imm (expt 2 8)) (error "offset too large" imm))
(emit `(4 . 5) ; opcode = 5
`(2 . ,(cadr flag)) ; flag selector
`(1 . 0) ; unused
`(1 . ,set) ; asserted (set / not set)
`(8 . ,imm)) ; offset
)
;; "Macros"
(define (emit-packed-string s)
;; emit length
(define sl (string-length s))
(u16 sl) ; cast to u16 to get bounds check
(emit sl)
;; compute packed words
(define words (pack-bytes-to-words (string->ascii-list s)))
(let loop ((ws words))
(if (null? ws)
;; if done, return total number of words emitted
(length words)
;; if not, emit the word and loop
(begin (emit (car ws))
(loop (cdr ws))))))
;; Utils
(define (type-of v)
(if (and (list? v)
(> (length v) 0))
(car v)
#f))
(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)))
(define (pack-bytes-to-words bytes)
(cond
((>= (length bytes) 2)
(let* ((hi (car bytes))
(lo (cadr bytes))
(word (+ (arithmetic-shift hi 8) lo)))
(unless (and (>= word 0)
(< word (expt 2 16)))
(error "packing of two bytes produced an invalid 16 bit word" word))
(cons word (pack-bytes-to-words (cddr bytes)))))
((= (length bytes) 1)
(let* ((hi (car bytes))
(word (arithmetic-shift hi 8)))
(unless (and (>= word 0)
(< word (expt 2 16)))
(error "packing of one byte produced an invalid 16 bit word" word))
(list word)))
((= (length bytes) 0)
'())))
|
