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Missing-parents

Exec-lbu

Semantics of the LBU instruction [ISA:2.6].

Signature
(exec-lbu rd rs1 imm stat feat) → new-stat
Arguments: rd — Guard (ubyte5p rd).; rs1 — Guard (ubyte5p rs1).; imm — Guard (ubyte12p imm).; stat — Guard (statp stat).; feat — Guard (featp feat).
Returns: new-stat — Type (statp new-stat).

We calculate the effective address. We read an unsigned 8-bit integer from the effective address, which is also implicitly zero-extended to XLEN bits. We write the result to rd. We increment the program counter.

Definitions and Theorems

Function: exec-lbu

(defun exec-lbu (rd rs1 imm stat feat)
  (declare (xargs :guard (and (ubyte5p rd)
                              (ubyte5p rs1)
                              (ubyte12p imm)
                              (statp stat)
                              (featp feat))))
  (declare (xargs :guard (stat-validp stat feat)))
  (let ((__function__ 'exec-lbu))
    (declare (ignorable __function__))
    (b* ((addr (eff-addr rs1 imm stat feat))
         (result (read-memory-unsigned8 addr stat feat))
         (stat (write-xreg (ubyte5-fix rd)
                           result stat feat))
         (stat (inc4-pc stat feat)))
      stat)))

Theorem: statp-of-exec-lbu

(defthm statp-of-exec-lbu
  (b* ((new-stat (exec-lbu rd rs1 imm stat feat)))
    (statp new-stat))
  :rule-classes :rewrite)

Theorem: exec-lbu-of-ubyte5-fix-rd

(defthm exec-lbu-of-ubyte5-fix-rd
  (equal (exec-lbu (ubyte5-fix rd)
                   rs1 imm stat feat)
         (exec-lbu rd rs1 imm stat feat)))

Theorem: exec-lbu-ubyte5-equiv-congruence-on-rd

(defthm exec-lbu-ubyte5-equiv-congruence-on-rd
  (implies (ubyte5-equiv rd rd-equiv)
           (equal (exec-lbu rd rs1 imm stat feat)
                  (exec-lbu rd-equiv rs1 imm stat feat)))
  :rule-classes :congruence)

Theorem: exec-lbu-of-ubyte5-fix-rs1

(defthm exec-lbu-of-ubyte5-fix-rs1
  (equal (exec-lbu rd (ubyte5-fix rs1)
                   imm stat feat)
         (exec-lbu rd rs1 imm stat feat)))

Theorem: exec-lbu-ubyte5-equiv-congruence-on-rs1

(defthm exec-lbu-ubyte5-equiv-congruence-on-rs1
  (implies (ubyte5-equiv rs1 rs1-equiv)
           (equal (exec-lbu rd rs1 imm stat feat)
                  (exec-lbu rd rs1-equiv imm stat feat)))
  :rule-classes :congruence)

Theorem: exec-lbu-of-ubyte12-fix-imm

(defthm exec-lbu-of-ubyte12-fix-imm
  (equal (exec-lbu rd rs1 (ubyte12-fix imm)
                   stat feat)
         (exec-lbu rd rs1 imm stat feat)))

Theorem: exec-lbu-ubyte12-equiv-congruence-on-imm

(defthm exec-lbu-ubyte12-equiv-congruence-on-imm
  (implies (acl2::ubyte12-equiv imm imm-equiv)
           (equal (exec-lbu rd rs1 imm stat feat)
                  (exec-lbu rd rs1 imm-equiv stat feat)))
  :rule-classes :congruence)

Theorem: exec-lbu-of-stat-fix-stat

(defthm exec-lbu-of-stat-fix-stat
  (equal (exec-lbu rd rs1 imm (stat-fix stat)
                   feat)
         (exec-lbu rd rs1 imm stat feat)))

Theorem: exec-lbu-stat-equiv-congruence-on-stat

(defthm exec-lbu-stat-equiv-congruence-on-stat
  (implies (stat-equiv stat stat-equiv)
           (equal (exec-lbu rd rs1 imm stat feat)
                  (exec-lbu rd rs1 imm stat-equiv feat)))
  :rule-classes :congruence)

Theorem: exec-lbu-of-feat-fix-feat

(defthm exec-lbu-of-feat-fix-feat
  (equal (exec-lbu rd rs1 imm stat (feat-fix feat))
         (exec-lbu rd rs1 imm stat feat)))

Theorem: exec-lbu-feat-equiv-congruence-on-feat

(defthm exec-lbu-feat-equiv-congruence-on-feat
  (implies (feat-equiv feat feat-equiv)
           (equal (exec-lbu rd rs1 imm stat feat)
                  (exec-lbu rd rs1 imm stat feat-equiv)))
  :rule-classes :congruence)