327 行
9.2 KiB
Racket
327 行
9.2 KiB
Racket
(define (alu-tab y)
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(case y
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[(0) 'RLC]
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[(1) 'RRC]
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[(2) 'RL]
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[(3) 'RR]
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[(4) 'SLA]
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[(5) 'SRA]
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[(6) 'SWAP]
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[(7) 'SRL]
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[else (error "unknown alu operation")]))
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(define (reg-tab z)
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(case z
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[(0) 'B]
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[(1) 'C]
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[(2) 'D]
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[(3) 'E]
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[(4) 'H]
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[(5) 'L]
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[(6) 'ind-HL]
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[(7) 'A]
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[else (error "unknown register index")]))
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(define (cc-tab z)
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(case z
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[(0) 'NZ]
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[(1) 'Z]
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[(2) 'NC]
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[(3) 'C]
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[else (error "unknown control index")]))
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(define (rp-tab y)
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(case
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[(0) 'BC]
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[(1) 'DE]
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[(2) 'HL]
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[(3) 'SP]
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[else (error "unknown register pair index")]))
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(define (rp2-tab y)
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(case
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[(0) 'BC]
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[(1) 'DE]
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[(2) 'HL]
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[(3) 'AF]
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[else (error "unknown register pair index")]))
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(define (non-prefix byte)
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(let ([x (arithmetic-shift (bitwise-and #b11000000 byte) -6)])
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(case x
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[(0) (dispatch-zero-x byte)]
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[(1) (dispatch-ld-r-r byte)]
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[(2) (dispatch-alu-x byte)]
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[(3) (dispatch-misc byte)]
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[else (error "malformed byte: " byte)])))
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(define (dispatch-misc byte)
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(let ([z (bitwise-and #b00000111 byte)])
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(case z
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[(0) (returns-and-misc byte)]
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[(1) (pop-ret-misc byte)]
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[(2) (cond-jps-and-misc-lds byte)]
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[(3) (uncond-jp-and-ints byte)]
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[(4) (cond-calls byte)]
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[(5) (push-and-call byte)]
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[(6) (imm-alu-ops byte)]
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[(7) (rst-vecs byte)])))
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(define (imm-alu-ops byte)
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(letrec ([y (arithmetic-shift (bitwise-and #b00111000 byte) -3)])
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(lambda x
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`(,(case y
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[(0) 'ADD]
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[(1) 'ADC]
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[(2) 'SUB]
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[(3) 'SBC]
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[(4) 'AND]
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[(5) 'XOR]
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[(6) 'OR]
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[(7) 'CP])
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,x))))
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(define (rst-vecs byte)
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(letrec ([y (arithmetic-shift (bitwise-and #b00111000 byte) -3)])
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`(RST ,(* y 8))))
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(define (push-and-call byte)
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(letrec ([y (arithmetic-shift (bitwise-and #b00111000 byte) -3)]
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[p (arithmetic-shift y -1)]
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[z (bitwise-and #b00000111 byte)])
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(case y
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[(0 1 2 3) `(PUSH ,(rp2-tab p))]
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[(4) (lambda y2 (lambda x `(CALL ,@(make-16b-addr x y2))))]
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[(5 6 7) '(REMOVED)])))
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(define (cond-calls byte)
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(let ([y (arithmetic-shift (bitwise-and #b00111000 byte) -3)]
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[z (bitwise-and #b00000111 byte)])
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(case y
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[(0 1 2 3) (lambda y2 (lambda x `(CALL ,(cc-tab y) ,(make-16b-addr x y2))))]
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[(4 5 6 7) '(REMOVED)])))
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(define (uncond-jp-and-ints byte)
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(let ([y (arithmetic-shift (bitwise-and #b00111000 byte) -3)]
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[z (bitwise-and #b00000111 byte)])
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(case y
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[(0) (lambda y (lambda x `(JP ,(make-16b-addr x y))))]
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[(1) '(CB-PREFIX)]
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[(2 3 4 5) '(REMOVED)]
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[(6) '(DI)]
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[(7) '(EI)])))
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(define (cond-jps-and-misc-lds byte)
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(let ([y (arithmetic-shift (bitwise-and #b00111000 byte) -3)]
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[z (bitwise-and #b00000111 byte)])
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(case y
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[(0 1 2 3) (lambda y2 (lambda x `(JP ,(cc-tab y) ,(make-16b-addr x y2))))]
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[(4) '(LD (ADD #xFF00 C) A)]
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[(5) (lambda y (lambda x `(LD ,(make-16b-addr x y) A)))]
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[(6) '(LD A (ADD #xFF00 C))]
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[(7) (lambda y (lambda x `(LD A ,(make-16b-addr x y))))])))
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(define (pop-ret-misc byte)
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(let ([y (arithmetic-shift (bitwise-and #b00111000 byte) -3)]
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[z (bitwise-and #b00000111 byte)])
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(case y
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[(0 1 2 3) `(POP ,(rp2-tab z))]
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[(4) '(RET)]
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[(5) '(RETI)]
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[(6) '(JP HL)]
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[(7) '(LD SP HL)])))
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(define (returns-and-misc byte)
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(let ([y (arithmetic-shift (bitwise-and #b00111000 byte) -3)]
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[z (bitwise-and #b00000111 byte)])
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(if (> y 4)
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`(RET ,(cc-tab y))
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(make-misc-ldh-and-sp (- y 4)))))
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(define (make-misc-ldh-and-sp y)
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(case y
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[(0) (lambda x `(LD ,(bitwise-ior #xFF00 x) A))]
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[(1) (lambda d `(ADD SP ,d))]
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[(2) (lambda x `(LD A ,(bitwise-ior #xFF00 x)))]
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[(3) (lambda d `(LD HL (ADD SP ,d)))]))
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(define (dispatch-alu-x byte)
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(let ([y (arithmetic-shift (bitwise-and #b00111000 byte) -3)]
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[z (bitwise-and #b00000111 byte)])
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(case y
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[(0) `(ADD ,(reg-tab z))]
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[(1) `(ADC ,(reg-tab z))]
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[(2) `(SUB ,(reg-tab z))]
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[(3) `(SBC ,(reg-tab z))]
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[(4) `(AND ,(reg-tab z))]
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[(5) `(XOR ,(reg-tab z))]
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[(6) `(OR ,(reg-tab z))]
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[(7) `(CP ,(reg-tab z))])))
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(define (dispatch-zero-x byte)
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(let ([z (bitwise-and #b00000111 byte)])
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(case z
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[(0) (relative-jp-and-misc byte)]
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[(1) (16b-ld-and-add byte)]
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[(2) (indirect-lds-a byte)]
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[(3) (16b-inc-dec byte)]
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[(4 5) (8b-inc-dec byte)]
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[(6) (8b-ld-imm byte)]
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[(7) (rots-and-misc byte)]
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[else (error "malformed instruction: " byte)])))
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(define (dispatch-ld-r-r byte)
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(let ([y (arithmetic-shift (bitwise-and #b00111000 byte) -3)]
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[z (bitwise-and #b00000111 byte)])
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`(LD ,(reg-tab y) ,(reg-tab z))))
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(define (rots-and-misc byte)
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(let ([y (arithmetic-shift (bitwise-and #b00111000 byte) -3)])
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(case y
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[(0) '(RLCA)]
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[(1) '(RRCA)]
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[(2) '(RLA)]
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[(3) '(RRA)]
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[(4) '(DAA)]
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[(5) '(CPL)]
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[(6) '(SCF)]
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[(7) '(CCF)])))
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(define (8b-ld-imm byte)
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(let ([y (arithmetic-shift (bitwise-and #b00111000 byte) -3)])
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(lambda x
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`(LD (REG ,(reg-tab y)) x))))
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(define (8b-inc-dec byte)
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(let ([y (arithmetic-shift (bitwise-and #b00111000 byte) -3)]
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[z (bitwise-and #b00000111 byte)])
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`(,(if (= 4 z) 'INC 'DEC) (REG ,(reg-tab y)))))
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(define (16b-inc-dec byte)
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(letrec ([y (arithmetic-shift (bitwise-and #b00111000 byte) -3)]
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[q (modulo y 2)]
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[p (arithmetic-shift y -1)])
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`(,(if (= 0 q) 'INC 'DEC) (REGP ,(rp-tab p)))))
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(define (indirect-lds-a byte)
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(letrec ([y (arithmetic-shift (bitwise-and #b00111000 byte) -3)]
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[q (modulo y 2)]
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[p (arithmetic-shift y -1)])
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(if (= 0 q)
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(make-ld-ind-p-a p)
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(make-ld-ind-a-p p))))
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(define (make-ld-ind-p-a p)
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(case p
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[(0) '(LD (IND BC) (REG A))]
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[(1) '(LD (IND DE) (REG A))]
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[(2) '(LDI (IND HL) (REG A))]
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[(3) '(LDD (IND HL) (REG A))]))
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(define (make-ld-ind-a-p p)
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(case p
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[(0) '(LD (REG A) (IND BC))]
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[(1) '(LD (REG A) (IND DE))]
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[(2) '(LDI (REG A) (IND HL))]
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[(3) '(LDD (REG A) (IND HL))]))
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(define (16b-ld-and-add byte)
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(letrec ([y (arithmetic-shift (bitwise-and #b00111000 byte) -3)]
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[q (modulo y 2)]
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[p (arithmetic-shift y -1)])
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(if (= 0 q)
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(make-16b-ld p)
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`(ADD (REGP HL) (REGP ,(rp-tab p))))))
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(define (relative-jp-and-misc byte)
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(let ([y (arithmetic-shift (bitwise-and #b00111000 byte) -3)])
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(case y
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[(0) '(NOP)]
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[(1) (create-ld-16b-ind 'SP)]
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[(2) '(STOP)]
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[(3) (make-jr '())]
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[(4 5 6 7) (make-jr y)]
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[else (error "malformed byte: " byte)])))
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(define (decode-cb-prefix byte)
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(letrec ([x (arithmetic-shift (bitwise-and #b11000000 byte) -6)]
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[y (arithmetic-shift (bitwise-and #b00111000 byte) -3)]
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[z (bitwise-and #b00000111 byte)])
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(case x
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[(0) `(,(alu-tab y) ,(reg-tab z))]
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[(1) `(BIT ,y ,(reg-tab z))]
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[(2) `(RES ,y ,(reg-tab z))]
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[(3) `(SET ,y ,(reg-tab z))])))
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(define (test bs)
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(car (read-instruction (set-bytes #x0000 bs (make-mem)))))
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(define (create-ld-16b-ind src)
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(lambda y
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(lambda x
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`(LD (IND ,(make-16b-addr x y)) ,src))))
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(define (make-16b-ld p)
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(lambda y
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(lambda x
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`(LD (REGP ,(rp-tab p)) (IND ,(make-16b-addr x y))))))
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(define (make-jr cc)
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`(JR ,(if (null? cc) 'no-check (cc-tab (- cc 4)))))
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(define (read-instruction m)
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(begin
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(define (ri-loop f npc)
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(if (not (procedure? f))
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(cons f (struct-copy mem m [pc npc]))
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(ri-loop (f (get-byte npc m)) (mod-16bit (add1 npc)))))
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(ri-loop decode-instr (mem-pc m))))
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(define (decode-instr byte)
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(if (or (>= byte 256) (< byte 0))
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(error "invalid opcode byte: " byte)
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(if (= byte #xCB)
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decode-cb-prefix
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(non-prefix byte))))
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(define (read-instruction m)
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(begin
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(define (ri-loop f npc)
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(if (not (procedure? f))
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(cons f (struct-copy mem m [pc npc]))
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(ri-loop (f (get-byte npc m)) (mod-16bit (add1 npc)))))
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(ri-loop decode-instr (mem-pc m))))
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(define (decode-instr byte)
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(if (or (>= byte 256) (< byte 0))
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(error "invalid opcode byte: " byte)
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(if (= byte #xCB)
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decode-cb-prefix
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(non-prefix byte))))
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(define (read-instruction m)
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(begin
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(define (ri-loop f npc)
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(if (not (procedure? f))
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(cons f (struct-copy mem m [pc npc]))
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(ri-loop (f (get-byte npc m)) (mod-16bit (add1 npc)))))
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(ri-loop decode-instr (mem-pc m))))
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(define (decode-instr byte)
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(if (or (>= byte 256) (< byte 0))
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(error "invalid opcode byte: " byte)
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(if (= byte #xCB)
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decode-cb-prefix
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(non-prefix byte))))
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