		Search-engine friendly clone of the ACL2 documentation.

Execution

Step

Single-step execution.

Signature
(step stat feat) → new-stat
Arguments: stat — Guard (statp stat).; feat — Guard (featp feat).
Returns: new-stat — Type (statp new-stat).

We make no change if the error flag is set. Otherwise, we read the program counter, we read the 32-bit encoding of the instruction from there, we decode it, and, if we obtain an instruction, we run the semantic function of the instruction; if decoding fails, we set the error flag instead.

Definitions and Theorems

Function: step

(defun step (stat feat)
  (declare (xargs :guard (and (statp stat) (featp feat))))
  (declare (xargs :guard (stat-validp stat feat)))
  (let ((__function__ 'step))
    (declare (ignorable __function__))
    (b* (((when (errorp stat feat))
          (stat-fix stat))
         (pc (read-pc stat feat))
         (enc (read-instruction pc stat feat))
         (instr? (decode enc feat))
         ((unless instr?) (error stat feat)))
      (exec-instr instr? pc stat feat))))

Theorem: statp-of-step

(defthm statp-of-step
  (b* ((new-stat (step stat feat)))
    (statp new-stat))
  :rule-classes :rewrite)

Theorem: stat-validp-of-step

(defthm stat-validp-of-step
  (implies (stat-validp stat feat)
           (b* ((?new-stat (step stat feat)))
             (stat-validp new-stat feat))))

Theorem: step-of-stat-fix-stat

(defthm step-of-stat-fix-stat
  (equal (step (stat-fix stat) feat)
         (step stat feat)))

Theorem: step-stat-equiv-congruence-on-stat

(defthm step-stat-equiv-congruence-on-stat
  (implies (stat-equiv stat stat-equiv)
           (equal (step stat feat)
                  (step stat-equiv feat)))
  :rule-classes :congruence)

Theorem: step-of-feat-fix-feat

(defthm step-of-feat-fix-feat
  (equal (step stat (feat-fix feat))
         (step stat feat)))

Theorem: step-feat-equiv-congruence-on-feat

(defthm step-feat-equiv-congruence-on-feat
  (implies (feat-equiv feat feat-equiv)
           (equal (step stat feat)
                  (step stat feat-equiv)))
  :rule-classes :congruence)