70 lines
2.2 KiB
Scheme
70 lines
2.2 KiB
Scheme
(define-module (scmvm language assembler)
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#:use-module (scmvm vm)
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#:use-module (scmvm language common)
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#:use-module (srfi srfi-1)
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#:use-module ((scheme base) #:select (write-bytevector))
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#:export (assemble))
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(define *aliases*
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'((if . branch)))
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(define (or-alias inst)
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(or (assq-ref *aliases* inst) inst))
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(define (lookup-instruction inst)
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(define inst-obj (assq (or-alias inst) *instruction-set*))
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(if inst-obj
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inst-obj
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(error (format #f "could not find instruction ~a" inst))))
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(define label? (compose not pair?))
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(define (variable? x)
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(and (pair? x) (eq? (car x) 'variable)))
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(define (ref? x)
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(and (pair? x) (eq? (car x) 'ref)))
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(define (set!? x)
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(and (pair? x) (eq? (car x) 'set!)))
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(define (instruction? x)
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(and (not (label? x))
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(not (variable? x))
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(not (ref? x))
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(not (set!? x))))
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(define (emit-instruction asm inst)
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(let ([inst-object (lookup-instruction (car inst))])
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(write-byte (instruction-code inst-object) asm)
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(assembler-pos-set! asm (+ (assembler-pos asm) 1))
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(when (not (null? (cdr inst)))
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(if (number? (cadr inst))
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(write-word (cadr inst) asm)
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(begin
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(write-word 0 asm)
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(assembler-label-add-reference asm (cadr inst) (assembler-pos asm))))
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(assembler-pos-set! asm (+ (assembler-pos asm) 4)))))
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(define (assemble-instructions asm inst-seq)
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(when (pair? inst-seq)
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(cond
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[(label? (car inst-seq))
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(emit-label asm (car inst-seq))]
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[(variable? (car inst-seq))
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(emit-label asm (second (car inst-seq)))
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(write-word (third (car inst-seq)) asm)
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(assembler-pos-set! asm (+ (assembler-pos asm) 4))]
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[(ref? (car inst-seq))
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(emit-instruction asm `(push ,(second (car inst-seq))))
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(emit-instruction asm '(@))]
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[(set!? (car inst-seq))
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(emit-instruction asm `(push ,(second (car inst-seq))))
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(emit-instruction asm '(!))]
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[else
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(emit-instruction asm (car inst-seq))])
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(assemble-instructions asm (cdr inst-seq))))
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(define (assemble instructions port)
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(define asm (make-assembler))
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(assemble-instructions asm instructions)
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(finalize-references asm)
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(write-bytevector (assembler-buf asm) port 0 (assembler-pos asm))
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asm)
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