src/wam/constants.lisp @ d4ba6547d8a1

(in-package #:bones.wam)

(define-constant +cell-width+ 16
  :documentation "Number of bits in each heap cell.")

(define-constant +cell-tag-width+ 2
  :documentation "Number of bits reserved for cell type tags.")

(define-constant +cell-value-width+ (- +cell-width+ +cell-tag-width+)
  :documentation "Number of bits reserved for cell values.")

(define-constant +cell-tag-bitmask+ #b11
  :documentation "Bitmask for masking the cell type tags.")


(define-constant +tag-null+      #b00
  :documentation "An empty cell.")

(define-constant +tag-structure+ #b01
  :documentation "A structure cell.")

(define-constant +tag-reference+ #b10
  :documentation "A pointer to a cell.")

(define-constant +tag-functor+   #b11
  :documentation "A functor.")


(define-constant +functor-arity-width+ 4
  :documentation "Number of bits dedicated to functor arity.")

(define-constant +functor-arity-bitmask+ #b1111
  :documentation "Bitmask for the functor arity bits.")


(define-constant +register-count+ 16
  :documentation "The number of registers the WAM has available.")

(define-constant +maximum-arity+ (1- (expt 2 +functor-arity-width+))
  :documentation "The maximum allowed arity of functors.")