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Diffstat (limited to 'lib/csc/encoding.csc')
| -rw-r--r-- | lib/csc/encoding.csc | 184 |
1 files changed, 184 insertions, 0 deletions
diff --git a/lib/csc/encoding.csc b/lib/csc/encoding.csc new file mode 100644 index 0000000..9afa40f --- /dev/null +++ b/lib/csc/encoding.csc @@ -0,0 +1,184 @@ +(define-library (csc encoding) + (export encode) + (import (scheme base) + (only (csc loop) + loop + return) + (only (csc match) match)) + (begin + ; I'm only going to say this once, so pay attention. + ; The format of unboxed constants is described in bytecocde/src/data.rs. + ; Boxed values are represented by a pointer to an array on the heap. The + ; first position in the array is an integer code indicating what type the + ; object is. Vectors have code 0, codes for other types are not stable. + ; Vectors are represented as an array, the first element of which is the + ; integer 0 (the type code), the second element is the vector length, and + ; the remaining slots hold the array values. + + + (define (low-byte w n) + (write-u8 (remainder n #x100) w)) + + + (define (64->le-bytes w n) + (low-byte w n) + (low-byte w (quotient n #x100)) + (low-byte w (quotient n #x10000)) + (low-byte w (quotient n #x1000000)) + (low-byte w (quotient n #x100000000)) + (low-byte w (quotient n #x10000000000)) + (low-byte w (quotient n #x1000000000000)) + (low-byte w (quotient n #x100000000000000))) + + + ; Bitwise-negates a 63-bit unsigned integer. + (define (bitwise-not n) + (loop with n* = 0 + for i from 1 to 63 + for n = n then (quotient n 2) + for digit = 1 then (* 2 digit) + if (even? n) + do (set! n* (+ n* digit)) + finally (return n*))) + + + (define (int->le-bytes w n) + (when (or (>= n #x4000000000000000) + (< n #x-4000000000000000)) + (error "int constant too large" n)) + (when (negative? n) + (set! n (remainder + (+ 1 (bitwise-not (- n))) + #x8000000000000000))) + (64->le-bytes w (+ 1 (* 2 n)))) + + + (define (bool->le-bytes w b) + (if b + (64->le-bytes w #xa) + (64->le-bytes w #x2))) + + + (define (const->le-bytes w x) + (cond + ((integer? x) + (int->le-bytes w x)) + ((boolean? x) + (bool->le-bytes w x)) + ((null? x) + (64->le-bytes w #x12)) + (else (error "unexpected type in const->le-bytes" x)))) + + + (define (make-opcode w code arg1-const arg2-const) + (when (>= code #x40) + (error "code is more than 6 bits" code)) + (define arg1-bit (if arg1-const + 2 + 0)) + (define arg2-bit (if arg2-const + 1 + 0)) + (write-u8 (+ (* 4 code) arg1-bit arg2-bit) w)) + + + (define (arg->le-bytes w atom) + (match atom + (('const val) (const->le-bytes w val)) + (('local i) + (when (>= i #x100) + (error "local index is out of range" i)) + (write-u8 i w)) + (_ (error "unexpected form in arg->le-bytes" atom)))) + + + (define (is-const? atom) + (match atom + (('const _) #t) + (_ #f))) + + + (define (opcode-switch w opcode) + (match opcode + (('mov dest src) + (make-opcode w 0 (is-const? src) #f) + (arg->le-bytes w dest) + (arg->le-bytes w src)) + (('jmpif test dest) + (make-opcode w 1 (is-const? test) (is-const? dest)) + (arg->le-bytes w test) + (arg->le-bytes w dest)) + (('jmp dest) + (make-opcode w 2 (is-const? dest) #f) + (arg->le-bytes w dest)) + (('alloc dest size) + (make-opcode w 3 (is-const? size) #f) + (arg->le-bytes w dest) + (arg->le-bytes w size)) + (('peek dest ptr offset) + (make-opcode w 4 (is-const? ptr) (is-const? offset)) ; ptr will likely never be constant. + (arg->le-bytes w dest) + (arg->le-bytes w ptr) + (arg->le-bytes w offset)) + (('poke word ('local ptr) offset) + ; We only have 2 bits to store whether the arguments are const, but + ; it's actually true that a pointer can never be a constant. So we + ; only track whether the word and offset arguments are constant, and + ; assume ptr will always be a one-byte register name. + (make-opcode w 5 (is-const? word) (is-const? offset)) + (arg->le-bytes w word) + (arg->le-bytes w (list 'local ptr)) + (arg->le-bytes w offset)) + (('add dest x y) + (make-opcode w 6 (is-const? x) (is-const? y)) + (arg->le-bytes w dest) + (arg->le-bytes w x) + (arg->le-bytes w y)) + (('sub dest x y) + (make-opcode w 7 (is-const? x) (is-const? y)) + (arg->le-bytes w dest) + (arg->le-bytes w x) + (arg->le-bytes w y)) + (('mul dest x y) + (make-opcode w 8 (is-const? x) (is-const? y)) + (arg->le-bytes w dest) + (arg->le-bytes w x) + (arg->le-bytes w y)) + (('div dest x y) + (make-opcode w 9 (is-const? x) (is-const? y)) + (arg->le-bytes w dest) + (arg->le-bytes w x) + (arg->le-bytes w y)) + (('mod dest x y) + (make-opcode w 10 (is-const? x) (is-const? y)) + (arg->le-bytes w dest) + (arg->le-bytes w x) + (arg->le-bytes w y)) + (('peekbyte dest ptr offset) + (make-opcode w 11 (is-const? ptr) (is-const? offset)) + (arg->le-bytes w dest) + (arg->le-bytes w ptr) + (arg->le-bytes w offset)) + (('pokebyte word ('local ptr) offset) + (make-opcode w 12 (is-const? word) (is-const? offset)) + (arg->le-bytes w word) + (arg->le-bytes w (list 'local ptr)) + (arg->le-bytes w offset)) + (('exit code) + (make-opcode w 13 (is-const? code) #f) + (arg->le-bytes w code)) + (('alloc-bytevector dest size) + (make-opcode w 14 (is-const? size) #f) + (arg->le-bytes w dest) + (arg->le-bytes w size)) + (('typeof dest x) + (make-opcode w 15 (is-const? x) #f) + (arg->le-bytes w dest) + (arg->le-bytes w x)) + (_ (error "invalid opcode" opcode)))) + + + (define (encode program) + (define out (open-output-bytevector)) + (map (lambda (op) (opcode-switch out op)) program) + (get-output-bytevector out)))) |