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Prefixes

Prefixes->seg

Access the |X86ISA|::|SEG| field of a prefixes bit structure.

Signature
(prefixes->seg x) → seg
Arguments: x — Guard (prefixes-p x).
Returns: seg — Type (8bits-p seg).

Definitions and Theorems

Function: prefixes->seg$inline

(defun prefixes->seg$inline (x)
  (declare (xargs :guard (prefixes-p x)))
  (mbe :logic
       (let ((x (prefixes-fix x)))
         (part-select x :low 20 :width 8))
       :exec (the (unsigned-byte 8)
                  (logand (the (unsigned-byte 8) 255)
                          (the (unsigned-byte 32)
                               (ash (the (unsigned-byte 52) x)
                                    -20))))))

Theorem: 8bits-p-of-prefixes->seg

(defthm 8bits-p-of-prefixes->seg
  (b* ((seg (prefixes->seg$inline x)))
    (8bits-p seg))
  :rule-classes :rewrite)

Theorem: prefixes->seg$inline-of-prefixes-fix-x

(defthm prefixes->seg$inline-of-prefixes-fix-x
  (equal (prefixes->seg$inline (prefixes-fix x))
         (prefixes->seg$inline x)))

Theorem: prefixes->seg$inline-prefixes-equiv-congruence-on-x

(defthm prefixes->seg$inline-prefixes-equiv-congruence-on-x
  (implies (prefixes-equiv x x-equiv)
           (equal (prefixes->seg$inline x)
                  (prefixes->seg$inline x-equiv)))
  :rule-classes :congruence)

Theorem: prefixes->seg-of-prefixes

(defthm prefixes->seg-of-prefixes
  (equal (prefixes->seg (prefixes num lck rep seg opr adr nxt))
         (8bits-fix seg)))

Theorem: prefixes->seg-of-write-with-mask

(defthm prefixes->seg-of-write-with-mask
 (implies
  (and
   (fty::bitstruct-read-over-write-hyps x prefixes-equiv-under-mask)
   (prefixes-equiv-under-mask x y fty::mask)
   (equal (logand (lognot fty::mask) 267386880)
          0))
  (equal (prefixes->seg x)
         (prefixes->seg y))))