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Sib->base

Access the |X86ISA|::|BASE| field of a sib bit structure.

Signature
(sib->base x) → base
Arguments: x — Guard (sib-p x).
Returns: base — Type (3bits-p base).

Definitions and Theorems

Function: sib->base$inline

(defun sib->base$inline (x)
  (declare (xargs :guard (sib-p x)))
  (mbe :logic
       (let ((x (sib-fix x)))
         (part-select x :low 0 :width 3))
       :exec (the (unsigned-byte 3)
                  (logand (the (unsigned-byte 3) 7)
                          (the (unsigned-byte 8) x)))))

Theorem: 3bits-p-of-sib->base

(defthm 3bits-p-of-sib->base
  (b* ((base (sib->base$inline x)))
    (3bits-p base))
  :rule-classes :rewrite)

Theorem: sib->base$inline-of-sib-fix-x

(defthm sib->base$inline-of-sib-fix-x
  (equal (sib->base$inline (sib-fix x))
         (sib->base$inline x)))

Theorem: sib->base$inline-sib-equiv-congruence-on-x

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

Theorem: sib->base-of-sib

(defthm sib->base-of-sib
  (equal (sib->base (sib base index scale))
         (3bits-fix base)))

Theorem: sib->base-of-write-with-mask

(defthm sib->base-of-write-with-mask
 (implies
   (and (fty::bitstruct-read-over-write-hyps x sib-equiv-under-mask)
        (sib-equiv-under-mask x y fty::mask)
        (equal (logand (lognot fty::mask) 7) 0))
   (equal (sib->base x) (sib->base y))))