81 lines
2.8 KiB
Scheme
81 lines
2.8 KiB
Scheme
(define-module (scmvm assembler)
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#:use-module (scmvm vm)
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#:use-module (srfi srfi-26)
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#:use-module (srfi srfi-9)
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#:use-module (rnrs bytevectors)
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#:use-module ((scheme base) #:select (write-bytevector))
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#:export ((make-assembler* . make-assembler)
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assembler?
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assembler-labels
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emit-label
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emit-instruction
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emit-literal
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emit-reference
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finalize-references
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assembler-dump-program))
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(define (make-label) (cons #f '()))
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(define-record-type <assembler>
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(make-assembler pos buf labels)
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assembler?
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(pos assembler-pos assembler-pos-set!)
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(buf assembler-buf assembler-buf-set!)
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(labels assembler-labels))
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(define (make-assembler*)
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(make-assembler 0 (make-bytevector 1024) (make-hash-table)))
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(define (assembler-buf-grow! asm)
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(let ([buf (make-bytevector (ash (bytevector-length (assembler-buf asm)) -1))])
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(bytevector-copy! (assembler-buf asm) 0 buf 0 (bytevector-length (assembler-buf asm)))
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(assembler-buf-set! asm buf)))
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(define* (write-word word asm #:optional (pos (assembler-pos asm)))
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(when (> (+ pos 4) (bytevector-length (assembler-buf asm)))
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(assembler-buf-grow! asm))
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(bytevector-u32-native-set! (assembler-buf asm) pos word))
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(define* (write-byte byte asm #:optional (pos (assembler-pos asm)))
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(when (> (+ pos 1) (bytevector-length (assembler-buf asm)))
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(assembler-buf-grow! asm))
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(bytevector-u8-set! (assembler-buf asm) pos byte))
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(define (assembler-label-add-reference asm name addr)
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(when (not (hash-ref (assembler-labels asm) name))
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(hash-set! (assembler-labels asm) name (make-label)))
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(let ([label (hash-ref (assembler-labels asm) name)])
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(set-cdr! label (cons addr (cdr label)))))
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(define (assembler-label-add-value asm name val)
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(when (not (hash-ref (assembler-labels asm) name))
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(hash-set! (assembler-labels asm) name (make-label)))
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;; 1+ to fudge for null pointers
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(set-car! (hash-ref (assembler-labels asm) name) (1+ val)))
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(define (emit-label asm name)
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(assembler-label-add-value asm name (assembler-pos asm)))
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(define (emit-instruction asm inst)
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(let ([inst-object (assq inst *instruction-set*)])
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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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(define (emit-literal asm val)
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(write-word val asm)
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(assembler-pos-set! asm (+ (assembler-pos asm) 4)))
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(define (emit-reference asm name)
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(assembler-label-add-reference asm name (assembler-pos asm))
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(assembler-pos-set! asm (+ (assembler-pos asm) 4)))
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(define (finalize-references asm)
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(define (install-location _name label)
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(for-each
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(cute write-word (car label) asm <>)
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(cdr label)))
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(hash-for-each install-location (assembler-labels asm)))
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(define (assembler-dump-program asm port)
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(write-bytevector (assembler-buf asm) port 0 (assembler-pos asm)))
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