		Search-engine friendly clone of the ACL2 documentation.

States

Write-pc

Write the program counter.

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

We pass an unsigned integer of arbitrary size, of which only the low XLEN bits are kept, and written to the program counter register.

[ISA:1.4] says that address computations wrap around ignoring overflow, i.e. the last address in the address space is adjacent to address 0. This function handles the wrapping around, see e.g. inc4-pc.

Definitions and Theorems

Function: write-pc

(defun write-pc (pc stat feat)
  (declare (xargs :guard (and (natp pc)
                              (statp stat)
                              (featp feat))))
  (declare (xargs :guard (stat-validp stat feat)))
  (let ((__function__ 'write-pc))
    (declare (ignorable __function__))
    (change-stat stat
                 :pc (loghead (feat->xlen feat)
                              (lnfix pc)))))

Theorem: statp-of-write-pc

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

Theorem: stat-validp-of-write-pc

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

Theorem: write-pc-of-nfix-pc

(defthm write-pc-of-nfix-pc
  (equal (write-pc (nfix pc) stat feat)
         (write-pc pc stat feat)))

Theorem: write-pc-nat-equiv-congruence-on-pc

(defthm write-pc-nat-equiv-congruence-on-pc
  (implies (acl2::nat-equiv pc pc-equiv)
           (equal (write-pc pc stat feat)
                  (write-pc pc-equiv stat feat)))
  :rule-classes :congruence)

Theorem: write-pc-of-stat-fix-stat

(defthm write-pc-of-stat-fix-stat
  (equal (write-pc pc (stat-fix stat) feat)
         (write-pc pc stat feat)))

Theorem: write-pc-stat-equiv-congruence-on-stat

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

Theorem: write-pc-of-feat-fix-feat

(defthm write-pc-of-feat-fix-feat
  (equal (write-pc pc stat (feat-fix feat))
         (write-pc pc stat feat)))

Theorem: write-pc-feat-equiv-congruence-on-feat

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