;;;; the ARM VM definition of character operations

;;;; This software is part of the SBCL system. See the README file for
;;;; more information.
;;;;
;;;; This software is derived from the CMU CL system, which was
;;;; written at Carnegie Mellon University and released into the
;;;; public domain. The software is in the public domain and is
;;;; provided with absolutely no warranty. See the COPYING and CREDITS
;;;; files for more information.

(in-package "SB-VM")

;;;; Moves and coercions:

;;; Move a tagged char to an untagged representation.
(define-vop (move-to-character)
  (:args (x :scs (any-reg descriptor-reg)))
  (:results (y :scs (character-reg)))
  (:note "character untagging")
  (:generator 1
     (inst lsr y x n-widetag-bits)))
(define-move-vop move-to-character :move
  (any-reg descriptor-reg) (character-reg))

;;; Move an untagged char to a tagged representation.
(define-vop (move-from-character)
  (:args (x :scs (character-reg)))
  (:results (y :scs (any-reg descriptor-reg)))
  (:note "character tagging")
  (:generator 1
    (inst lsl y x n-widetag-bits)
    (inst add y y character-widetag)))
(define-move-vop move-from-character :move
  (character-reg) (any-reg descriptor-reg))

;;; Move untagged character values.
(define-vop (character-move)
  (:args (x :target y
            :scs (character-reg)
            :load-if (not (location= x y))))
  (:results (y :scs (character-reg)
               :load-if (not (location= x y))))
  (:note "character move")
  (:generator 0
    (move y x)))
(define-move-vop character-move :move
  (character-reg) (character-reg))

;;; Move untagged character arguments/return-values.
(define-vop (move-character-arg)
  (:args (x :target y
            :scs (character-reg))
         (fp :scs (any-reg)
             :load-if (not (sc-is y character-reg))))
  (:results (y))
  (:note "character arg move")
  (:generator 0
    (sc-case y
      (character-reg
       (move y x))
      (character-stack
       (store-stack-offset x fp y)))))
(define-move-vop move-character-arg :move-arg
  (any-reg character-reg) (character-reg))

;;; Use standard MOVE-ARG + coercion to move an untagged character
;;; to a descriptor passing location.
(define-move-vop move-arg :move-arg
  (character-reg) (any-reg descriptor-reg))

;;;; Other operations:
(define-vop (char-code)
  (:translate char-code)
  (:policy :fast-safe)
  (:args (ch :scs (character-reg)))
  (:arg-types character)
  (:results (res :scs (any-reg)))
  (:result-types positive-fixnum)
  (:generator 1
    (inst lsl res ch n-fixnum-tag-bits)))

(define-vop (code-char)
  (:translate code-char)
  (:policy :fast-safe)
  (:args (code :scs (any-reg)))
  (:arg-types positive-fixnum)
  (:results (res :scs (character-reg)))
  (:result-types character)
  (:generator 1
    (inst lsr res code n-fixnum-tag-bits)))

(define-vop (character-compare)
  (:args (x :scs (character-reg))
         (y :scs (character-reg)))
  (:arg-types character character)
  (:policy :fast-safe)
  (:note "inline comparison")
  (:generator 3
    (inst cmp x y)))

(define-vop (fast-char=/character character-compare)
  (:translate char=)
  (:conditional :eq))

(define-vop (fast-char>/character character-compare)
  (:translate char>)
  (:conditional :gt))

(define-vop (fast-char</character character-compare)
  (:translate char<)
  (:conditional :lt))

(defun char-immediate-p (char)
  (and (characterp char)
       (add-sub-immediate-p (char-code char))))

(define-vop (character-compare/c)
  (:args (x :scs (character-reg)))
  (:arg-types character (:constant (satisfies char-immediate-p)))
  (:info y)
  (:policy :fast-safe)
  (:note "inline constant comparison")
  (:generator 2
    (inst cmp x (char-code y))))

(define-vop (fast-char=/character/c character-compare/c)
  (:translate char=)
  (:conditional :eq))

(define-vop (fast-char>/character/c character-compare/c)
  (:translate char>)
  (:conditional :gt))

(define-vop (fast-char</character/c character-compare/c)
  (:translate char<)
  (:conditional :lt))

#+sb-unicode
(define-vop (base-char-p)
  (:args (value :scs (any-reg descriptor-reg)))
  (:arg-types *)
  (:translate base-char-p)
  (:temporary (:sc unsigned-reg :from (:argument 0)) temp)
  (:conditional :eq)
  (:policy :fast-safe)
  (:generator 4
    (inst and temp value (lognot #x7F00))
    (inst cmp temp character-widetag)))

#+sb-unicode
(define-vop (base-char-p-character)
  (:args (value :scs (any-reg)))
  (:arg-types character)
  (:translate base-char-p)
  (:conditional :eq)
  (:policy :fast-safe)
  (:generator 3
    (inst tst value (lognot #x7FFF))))

#+sb-unicode
(define-vop (base-char-p-character-reg)
  (:args (value :scs (character-reg)))
  (:arg-types character)
  (:translate base-char-p)
  (:conditional :lt)
  (:policy :fast-safe)
  (:generator 2
    (inst cmp value base-char-code-limit)))

(defoptimizer (sb-c::vop-optimize move-to-character) (vop)
  (when (sb-c:next-vop-is vop 'char-code)
    (sb-c:replace-vops 2 vop 'tagged-char-code)))

;;; Exploit the fact that the MSB of character-widetag is 0 and that n-fixnum-tag-bits is 1.
(eval-when (:compile-toplevel)
  (assert (not (logbitp 7 character-widetag))))
(define-vop (tagged-char-code)
  (:args (x :scs (any-reg descriptor-reg)))
  (:results (y :scs (any-reg descriptor-reg)))
  (:note "character untagging")
  (:generator 1
    (inst lsr y x (- n-widetag-bits n-fixnum-tag-bits))))

(defoptimizer (sb-c::vop-optimize code-char) (vop)
  (when (sb-c:next-vop-is vop 'move-from-character)
    (sb-c:replace-vops 2 vop 'tagged-code-char)))

(define-vop (tagged-code-char)
  (:args (x :scs (any-reg descriptor-reg)))
  (:results (y :scs (any-reg descriptor-reg)))
  (:note "character tagging")
  (:generator 1
    (inst lsl y x (- n-widetag-bits n-fixnum-tag-bits))
    (inst add y y character-widetag)))
