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Rflag-specifications

Sub-af-spec64

Signature
(sub-af-spec64 dst src) → *

Definitions and Theorems

Function: sub-af-spec64$inline

(defun sub-af-spec64$inline (dst src)
  (declare (type (unsigned-byte 64) dst)
           (type (unsigned-byte 64) src))
  (b* (((the (unsigned-byte 4) dst-3-0)
        (mbe :logic (part-select dst :low 0 :width 4)
             :exec (logand 15 dst)))
       ((the (unsigned-byte 4) src-3-0)
        (mbe :logic (part-select src :low 0 :width 4)
             :exec (logand 15 src)))
       (sub (the (signed-byte 5)
                 (- (the (unsigned-byte 4) dst-3-0)
                    (the (unsigned-byte 4) src-3-0))))
       (af (the (unsigned-byte 1)
                (bool->bit (< sub 0)))))
    af))

Theorem: n01p-sub-af-spec64

(defthm n01p-sub-af-spec64
 (unsigned-byte-p 1 (sub-af-spec64 dst src))
 :rule-classes
 (:rewrite
  (:type-prescription
     :corollary (bitp (sub-af-spec64 dst src))
     :hints
     (("Goal"
           :in-theory
           '(unsigned-byte-p integer-range-p natp bitp (:e expt)))))
  (:linear
   :corollary (and (<= 0 (sub-af-spec64 dst src))
                   (< (sub-af-spec64 dst src) 2))
   :hints
   (("Goal"
        :in-theory '(unsigned-byte-p integer-range-p (:e expt)))))))