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Semantics

Exec-lb

Semantics of the LB instruction [ISA:2.6].

Signature
(exec-lb 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, and sign-extend it to XLEN bits. We write the result to rd. We increment the program counter.

Definitions and Theorems

Function: exec-lb

(defun exec-lb (rd rs1 imm stat feat)
 (declare (xargs :guard (and (ubyte5p rd)
                             (ubyte5p rs1)
                             (ubyte12p imm)
                             (statp stat)
                             (featp feat))))
 (declare (xargs :guard (and (stat-validp stat feat)
                             (< (lnfix rd) (feat->xnum feat))
                             (< (lnfix rs1) (feat->xnum feat)))))
 (let ((__function__ 'exec-lb))
   (declare (ignorable __function__))
   (b*
    ((addr (eff-addr rs1 imm stat feat))
     (result
          (loghead (feat->xlen feat)
                   (logext 8
                           (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-lb

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

Theorem: stat-validp-of-exec-lb

(defthm stat-validp-of-exec-lb
  (implies (and (stat-validp stat feat)
                (< (lnfix rd) (feat->xnum feat)))
           (b* ((?new-stat (exec-lb rd rs1 imm stat feat)))
             (stat-validp new-stat feat))))

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

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

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

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

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

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

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

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

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

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

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

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

Theorem: exec-lb-of-stat-fix-stat

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

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

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

Theorem: exec-lb-of-feat-fix-feat

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

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

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