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;; Assume that core.scm is loaded
(define *unique-counter* 0)
(define (next-unique)
(inc! *unique-counter*)
*unique-counter*)
(define *macro-scratch-reg* R11)
(define (%packed-string s)
;; emit length
(define sl (string-length s))
(u16 sl) ; cast to u16 to get bounds check
(emit-word sl)
;; compute packed words
(for-each (@ emit-byte) (string->ascii-list s)))
(define-syntax emit-test-eq
(syntax-rules ()
((_ lhs rhs dest set)
(begin (sub lhs rhs)
(br flag-zero (label dest) set: set)))))
(define-syntax emit-test-lt
(syntax-rules ()
((_ lhs rhs dest set)
(begin (sub lhs rhs)
(br flag-sign (label dest) set: set)))))
(define-syntax emit-test-lte
(syntax-rules ()
((_ lhs rhs dest set)
(begin (sub lhs rhs)
(sub lhs (u16 1))
(br flag-sign (label dest) set: set)))))
(define-syntax emit-inverted-test
;; jump to dest if <lhs op rhs> is NOT true.
;; as such the behaviour of this macro can be considered to
;; be inverted.
;; the reason for this is to allow having the true branch
;; before the false branch in memory (arbitrary decision).
(syntax-rules ()
((_ lhs op rhs dest)
(cond
((eq? '== op) (emit-test-eq lhs rhs dest #f))
((eq? '!= op) (emit-test-eq lhs rhs dest #t))
((eq? '< op) (emit-test-lt lhs rhs dest #f))
((eq? '>= op) (emit-test-lt lhs rhs dest #t))
((eq? '<= op) (emit-test-lte lhs rhs dest #f))
((eq? '> op) (emit-test-lte lhs rhs dest #t))
(else (error "unsupported operator" op))))))
(define-syntax %if-else
(syntax-rules ()
((_ pred tb fb)
(let* ((lhs (eval (car `pred)))
(op (cadr 'pred))
(rhs (eval (caddr `pred)))
(n (next-unique))
(sym-false (string->symbol (format "~A-false" n)))
(sym-end (string->symbol (format "~A-end" n))))
(ld *macro-scratch-reg* lhs)
(emit-inverted-test *macro-scratch-reg* op rhs sym-false)
tb
(ld PC ZR (label sym-end))
(def-label sym-false)
fb
(def-label sym-end)))))
(define-syntax %when
(syntax-rules ()
((_ pred body body* ...)
(let* ((lhs (eval (car `pred)))
(op (cadr 'pred))
(rhs (eval (caddr `pred)))
(n (next-unique))
(sym-end (string->symbol (format "~A-end" n))))
(ld *macro-scratch-reg* lhs)
(emit-inverted-test *macro-scratch-reg* op rhs sym-end)
body body* ...
(def-label sym-end)))))
(define-syntax %while
(syntax-rules ()
((_ pred body body* ...)
(let* ((lhs (eval (car `pred)))
(op (cadr 'pred))
(rhs (eval (caddr `pred)))
(n (next-unique))
(sym-test (string->symbol (format "~A-test" n)))
(sym-end (string->symbol (format "~A-end" n))))
(ld *macro-scratch-reg* lhs)
(def-label sym-test)
(emit-inverted-test *macro-scratch-reg* op rhs sym-end)
body body* ...
(ld PC ZR (label sym-test))
(def-label sym-end)))))
(define *procedures* '())
(define-syntax %decl-proc
(syntax-rules ()
((_ signature)
(set! *procedures*
(cons `signature *procedures*))
)))
(define *proc-scope* (make-parameter #f))
(define (param pname)
(let* ((scope (or (*proc-scope*)
(error "cannot use params outside a procedure context"))))
(or (assocdr pname (*proc-scope*))
(error "no such param" pname))))
(define-syntax %param
(syntax-rules ()
((_ pname)
(param 'pname))))
(define-syntax %proc
(syntax-rules ()
((_ signature body* ...)
(let* ((name (car `signature))
(params (cdr `signature))
(bindings (zip params
(map (@ reg) (iota (length params) 0))))
(n-max-params 12))
(unless (<= (length params) n-max-params)
(error (format "proc has too many params (~A > ~A)" (length params) n-max-params)))
(%decl-proc signature)
(def-label name)
(parameterize ((*proc-scope* bindings))
body* ...)
(ld PC SP #f preinc: #t indirect: 1)
))))
(define-syntax %call
(syntax-rules ()
((_ name args* ...)
(let* ((params (or (assocdr `name *procedures*)
(error "proc not defined" `name)))
(args (list args* ...))
(n (next-unique))
(sym-ret (string->symbol (format "~A-ret" n))))
(unless (= (length params) (length args))
(error (format "incorrect args to ~A, expected ~A, got ~A" `name params args)))
(let loop ((i 0))
(when (< i (length args))
;; check that there are no reg arguments in later positions
;; that would be clobered/invalidated by a move
(let loop ((j (+ i 1)))
(when (< j (length args))
(let* ((jarg (list-ref args j))
(jtype (type-of jarg))
(jval (val-of jarg)))
(when (and (eq? 'reg jtype)
(eq? i jval))
(error "proc call would clobber register before it is moved" jarg '(name args* ...))))
(loop (+ j 1))))
;; move each argument to its designated register
;; first arg to R0, etc.
(let* ((rn (reg i))
(argi (list-ref args i))
(itype (type-of argi)))
(cond
((eq? 'reg itype)
(ld rn argi))
((or (eq? 'imm itype)
(eq? 'label itype))
(ld rn ZR argi))
(else (error "invalid argument" argi))))
(loop (+ 1 i))))
(ld *macro-scratch-reg* ZR (label sym-ret))
(st *macro-scratch-reg* SP #f postdec: #t)
(ld PC ZR (label `name))
(def-label sym-ret)
))))
(define (spush datum)
(cond
((eq? 'reg (type-of datum))
(st datum SP push: #t))
(else
(ld *macro-scratch-reg* datum)
(st *macro-scratch-reg* SP push: #t indirect: 1))))
(define (spop reg)
(unless (eq? 'reg (type-of reg))
(error "not a register" reg))
(ld reg SP pop: #t indirect: 1))
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