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Semantics32

Exec32-lbu

Semantics of the LBU instruction [ISA:2.6].

Signature
(exec32-lbu rd rs1 imm stat) → new-stat
Arguments: rd — Guard (ubyte5p rd).; rs1 — Guard (ubyte5p rs1).; imm — Guard (ubyte12p imm).; stat — Guard (state32p stat).
Returns: new-stat — Type (state32p 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 32 bits. We write the result to rd. We increment the program counter.

Definitions and Theorems

Function: exec32-lbu

(defun exec32-lbu (rd rs1 imm stat)
  (declare (xargs :guard (and (ubyte5p rd)
                              (ubyte5p rs1)
                              (ubyte12p imm)
                              (state32p stat))))
  (let ((__function__ 'exec32-lbu))
    (declare (ignorable __function__))
    (b* ((addr (eff32-addr rs1 imm stat))
         (result (read32-mem-ubyte8 addr stat))
         (stat (write32-xreg rd result stat))
         (stat (inc32-pc stat)))
      stat)))

Theorem: state32p-of-exec32-lbu

(defthm state32p-of-exec32-lbu
  (b* ((new-stat (exec32-lbu rd rs1 imm stat)))
    (state32p new-stat))
  :rule-classes :rewrite)

Theorem: exec32-lbu-of-ubyte5-fix-rd

(defthm exec32-lbu-of-ubyte5-fix-rd
  (equal (exec32-lbu (ubyte5-fix rd)
                     rs1 imm stat)
         (exec32-lbu rd rs1 imm stat)))

Theorem: exec32-lbu-ubyte5-equiv-congruence-on-rd

(defthm exec32-lbu-ubyte5-equiv-congruence-on-rd
  (implies (ubyte5-equiv rd rd-equiv)
           (equal (exec32-lbu rd rs1 imm stat)
                  (exec32-lbu rd-equiv rs1 imm stat)))
  :rule-classes :congruence)

Theorem: exec32-lbu-of-ubyte5-fix-rs1

(defthm exec32-lbu-of-ubyte5-fix-rs1
  (equal (exec32-lbu rd (ubyte5-fix rs1)
                     imm stat)
         (exec32-lbu rd rs1 imm stat)))

Theorem: exec32-lbu-ubyte5-equiv-congruence-on-rs1

(defthm exec32-lbu-ubyte5-equiv-congruence-on-rs1
  (implies (ubyte5-equiv rs1 rs1-equiv)
           (equal (exec32-lbu rd rs1 imm stat)
                  (exec32-lbu rd rs1-equiv imm stat)))
  :rule-classes :congruence)

Theorem: exec32-lbu-of-ubyte12-fix-imm

(defthm exec32-lbu-of-ubyte12-fix-imm
  (equal (exec32-lbu rd rs1 (ubyte12-fix imm)
                     stat)
         (exec32-lbu rd rs1 imm stat)))

Theorem: exec32-lbu-ubyte12-equiv-congruence-on-imm

(defthm exec32-lbu-ubyte12-equiv-congruence-on-imm
  (implies (acl2::ubyte12-equiv imm imm-equiv)
           (equal (exec32-lbu rd rs1 imm stat)
                  (exec32-lbu rd rs1 imm-equiv stat)))
  :rule-classes :congruence)

Theorem: exec32-lbu-of-state32-fix-stat

(defthm exec32-lbu-of-state32-fix-stat
  (equal (exec32-lbu rd rs1 imm (state32-fix stat))
         (exec32-lbu rd rs1 imm stat)))

Theorem: exec32-lbu-state32-equiv-congruence-on-stat

(defthm exec32-lbu-state32-equiv-congruence-on-stat
  (implies (state32-equiv stat stat-equiv)
           (equal (exec32-lbu rd rs1 imm stat)
                  (exec32-lbu rd rs1 imm stat-equiv)))
  :rule-classes :congruence)