feat: add support for ARMv7 pointers

[cfung89]

Hello, I found several errors regarding pointers in ARMv7 (or missing features). Here are several examples underlining the different issues that I have attempted to solve.

For LDR A3, [A1, V2]:

Before:

(program ; [0, 0] - [1, 0]
  (instruction ; [0, 0] - [0, 16]
    kind: (word) ; [0, 0] - [0, 3]
    (ident ; [0, 4] - [0, 6]
      (reg ; [0, 4] - [0, 6]
        (word))) ; [0, 4] - [0, 6]
    (ptr ; [0, 8] - [0, 16]
      (ERROR ; [0, 9] - [0, 12]
        (reg ; [0, 9] - [0, 11]
          (word))) ; [0, 9] - [0, 11]
      (reg ; [0, 13] - [0, 15]
        (word))))) ; [0, 13] - [0, 15]

After:

(program ; [0, 0] - [1, 0]
  (instruction ; [0, 0] - [0, 16]
    kind: (word) ; [0, 0] - [0, 3]
    (ident ; [0, 4] - [0, 6]
      (reg ; [0, 4] - [0, 6]
        (word))) ; [0, 4] - [0, 6]
    (ptr ; [0, 8] - [0, 16]
      (reg ; [0, 9] - [0, 11]
        (word)) ; [0, 9] - [0, 11]
      (reg ; [0, 13] - [0, 15]
        (word))))) ; [0, 13] - [0, 15]

Here, only integers were expected in the second argument of the pointer, whereas other registers are also aloud too.

---

For LDR A3, [A1, V2, LSL#2]:

Before:

(program ; [0, 0] - [1, 0]
  (instruction ; [0, 0] - [0, 7]
    kind: (word) ; [0, 0] - [0, 3]
    (ident ; [0, 4] - [0, 6]
      (reg ; [0, 4] - [0, 6]
        (word)))) ; [0, 4] - [0, 6]
  (ERROR ; [0, 8] - [1, 0]
    (reg ; [0, 9] - [0, 11]
      (word)) ; [0, 9] - [0, 11]
    (word) ; [0, 13] - [0, 15]
    (word) ; [0, 17] - [0, 20]
    (line_comment))) ; [0, 20] - [0, 23]

After:

(program ; [0, 0] - [1, 0]
  (instruction ; [0, 0] - [0, 23]
    kind: (word) ; [0, 0] - [0, 3]
    (ident ; [0, 4] - [0, 6]
      (reg ; [0, 4] - [0, 6]
        (word))) ; [0, 4] - [0, 6]
    (ptr ; [0, 8] - [0, 23]
      (reg ; [0, 9] - [0, 11]
        (word)) ; [0, 9] - [0, 11]
      (reg ; [0, 13] - [0, 15]
        (word)) ; [0, 13] - [0, 15]
      (instruction ; [0, 17] - [0, 20]
        kind: (word)) ; [0, 17] - [0, 20]
      (int)))) ; [0, 20] - [0, 22]

Here, LSL was considered as a register, and #2 as a comment, whereas LSL should be an instruction and #2 should be an integer. This is an ARMv7 feature used to shift the offset of a pointer (if present, the third argument is always some shift instruction followed by an integer).

---

For: LDR A3, [A2], V3, LSL#2

Before:

(program ; [0, 0] - [1, 0]
  (instruction ; [0, 0] - [0, 21]
    kind: (word) ; [0, 0] - [0, 3]
    (ident ; [0, 4] - [0, 6]
      (reg ; [0, 4] - [0, 6]
        (word))) ; [0, 4] - [0, 6]
    (ptr ; [0, 8] - [0, 12]
      (reg ; [0, 9] - [0, 11]
        (word))) ; [0, 9] - [0, 11]
    (ident ; [0, 14] - [0, 16]
      (reg ; [0, 14] - [0, 16]
        (word))) ; [0, 14] - [0, 16]
    (ident ; [0, 18] - [0, 21]
      (reg ; [0, 18] - [0, 21]
        (word)))) ; [0, 18] - [0, 21]
  (line_comment)) ; [0, 21] - [0, 23]

After:

(program ; [0, 0] - [1, 0]
  (instruction ; [0, 0] - [0, 23]
    kind: (word) ; [0, 0] - [0, 3]
    (ident ; [0, 4] - [0, 6]
      (reg ; [0, 4] - [0, 6]
        (word))) ; [0, 4] - [0, 6]
    (ptr ; [0, 8] - [0, 23]
      (reg ; [0, 9] - [0, 11]
        (word)) ; [0, 9] - [0, 11]
      (reg ; [0, 14] - [0, 16]
        (word)) ; [0, 14] - [0, 16]
      (instruction ; [0, 18] - [0, 21]
        kind: (word)) ; [0, 18] - [0, 21]
      (int)))) ; [0, 21] - [0, 23]

The error here was similar to the 2nd example. However, I added support for post-increment of the register pointer (which is outside of the square brackets).

---

Thank you very much! Let me know if there are any changes/improvements you would like me to make!

[RubixDev]

This will need to be rebased on main, and I've got a couple of questions, but otherwise looks good :)

[cfung89]

Thanks for the quick review. I made the requested changes. Let me know if I need to fix anything else!