DIE pass visits blocks in wrong order and can remove still-used instructions

[jfecher]

Aim

Performing DIE on the following brillig code (our loop test):

brillig(inline) fn main f0 {
  b0(v0: u32):
    v35 = allocate
    store u32 0 at v35
    jmp b1(u32 0)
  b1(v3: u32):
    v36 = lt v3, u32 4
    jmpif v36 then: b2, else: b3
  b2():
    v46 = load v35
    v47 = add v46, v3
    store v47 at v35
    v48 = add v3, u32 1
    jmp b1(v48)
  b3():
    v37 = load v35
    v38 = eq v37, v0
    constrain v37 == v0
    v39 = allocate
    store u32 0 at v39
    jmp b4(u32 0)
  b4(v13: u32):
    v40 = lt v13, u32 4
    jmpif v40 then: b5, else: b6
  b5():
    v43 = load v39
    v44 = add v43, v13
    store v44 at v39
    v45 = add v13, u32 1
    jmp b4(v45)
  b6():
    v41 = load v39
    v42 = eq v41, v0
    constrain v41 == v0
    return 
}
b0 -> b1 <-> b2
          -> b3 -> b4 <-> b5
                       -> b6

Expected Behavior

The visit order of the blocks should be:
b6, b4, b5, b3, b1, b2, b0
or
b6, b5, b4, b3, b2, b1, b0

Bug

The visit order of the blocks is actually:
b2, b5, b6, b4, b3, b1, b0

To Reproduce

Workaround

None

Workaround Description

No response

Additional Context

No response

Project Impact

None

Blocker Context

No response

Nargo Version

No response

NoirJS Version

No response

Proving Backend Tooling & Version

No response

Would you like to submit a PR for this Issue?

None

Support Needs

No response

[jfecher]

As far as I can tell the only reason this doesn't cause errors already is because we don't remove stores from DIE and other instructions typically can't be accessed after a loop in that way without introducing a new ValueId.