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X86-decoder

Three-byte-opcode-decode-and-execute

Decoder and dispatch function for three-byte opcodes, where 0x0F 0x38 are the first two opcode bytes

Signature
(three-byte-opcode-decode-and-execute proc-mode start-rip temp-rip prefixes rex-byte second-escape-byte x86) → x86

Source: Intel Manual, Volume 2, Appendix A-2

Definitions and Theorems

Function: three-byte-opcode-decode-and-execute

(defun three-byte-opcode-decode-and-execute
       (proc-mode start-rip temp-rip prefixes
                  rex-byte second-escape-byte x86)
 (declare (xargs :stobjs (x86)))
 (declare (type (integer 0 4) proc-mode)
          (type (signed-byte 48) start-rip)
          (type (signed-byte 48) temp-rip)
          (type (unsigned-byte 52) prefixes)
          (type (unsigned-byte 8) rex-byte)
          (type (unsigned-byte 8)
                second-escape-byte))
 (declare (xargs :guard (or (equal second-escape-byte 56)
                            (equal second-escape-byte 58))))
 (let ((__function__ 'three-byte-opcode-decode-and-execute))
  (declare (ignorable __function__))
  (b*
   ((ctx 'three-byte-opcode-decode-and-execute)
    ((mv flg0 (the (unsigned-byte 8) opcode)
         x86)
     (rme08 proc-mode temp-rip 1 :x x86))
    ((when flg0)
     (!!ms-fresh :opcode-byte-access-error flg0))
    ((mv flg temp-rip)
     (add-to-*ip proc-mode temp-rip 1 x86))
    ((when flg)
     (!!ms-fresh :increment-error flg))
    ((the (unsigned-byte 8) mandatory-prefix)
     (compute-mandatory-prefix-for-three-byte-opcode
          proc-mode
          second-escape-byte opcode prefixes))
    (modr/m? (three-byte-opcode-modr/m-p proc-mode mandatory-prefix
                                         second-escape-byte opcode))
    ((mv flg1 (the (unsigned-byte 8) modr/m)
         x86)
     (if modr/m? (rme08 proc-mode temp-rip 1 :x x86)
       (mv nil 0 x86)))
    ((when flg1)
     (!!ms-fresh :modr/m-byte-read-error flg1))
    ((mv flg temp-rip)
     (if modr/m? (add-to-*ip proc-mode temp-rip 1 x86)
       (mv nil temp-rip)))
    ((when flg)
     (!!ms-fresh :increment-error flg))
    (sib?
      (and modr/m?
           (b* ((p4? (eql 103 (prefixes->adr prefixes)))
                (16-bit-addressp
                     (eql 2
                          (select-address-size proc-mode p4? x86))))
             (x86-decode-sib-p modr/m 16-bit-addressp))))
    ((mv flg2 (the (unsigned-byte 8) sib)
         x86)
     (if sib? (rme08 proc-mode temp-rip 1 :x x86)
       (mv nil 0 x86)))
    ((when flg2)
     (!!ms-fresh :sib-byte-read-error flg2))
    ((mv flg temp-rip)
     (if sib? (add-to-*ip proc-mode temp-rip 1 x86)
       (mv nil temp-rip)))
    ((when flg)
     (!!ms-fresh :increment-error flg)))
   (case second-escape-byte
    (56 (first-three-byte-opcode-execute
             proc-mode
             start-rip temp-rip prefixes rex-byte
             mandatory-prefix opcode modr/m sib x86))
    (58 (second-three-byte-opcode-execute
             proc-mode
             start-rip temp-rip prefixes rex-byte
             mandatory-prefix opcode modr/m sib x86))
    (otherwise
     (!!ms-fresh
       :illegal-value-of-second-escape-byte second-escape-byte))))))

Theorem: x86p-three-byte-opcode-decode-and-execute

(defthm x86p-three-byte-opcode-decode-and-execute
  (implies (x86p x86)
           (x86p (three-byte-opcode-decode-and-execute
                      proc-mode start-rip temp-rip
                      prefixes rex-byte escape-byte x86))))