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Find the mistake in this ARM code:

medium📝 Analysis Q7 of 15
ARM Architecture - Control Flow Instructions
Find the mistake in this ARM code:
CMP R7, R8
BGE greater_equal_label
BLT less_label
ABGE and BLT conditions overlap incorrectly
BNo mistake, behavior is expected
CCMP should be SUBS
DFlags are not set correctly
Step-by-Step Solution
Solution:
  1. Step 1: Understand CMP and flags

    CMP R7, R8 sets flags correctly for signed comparison (R7 - R8).
  2. Step 2: Analyze branch conditions

    BGE (N == V) branches for greater or equal signed. If false (N != V), falls through to BLT (N != V), which branches for less than.
  3. Step 3: Verify no issues

    Conditions are mutually exclusive and exhaustive--no overlap, no gaps, correct behavior.
  4. Final Answer:

    No mistake, behavior is expected -> Option B
  5. Quick Check:

    BGE + BLT covers all signed cases [OK]
Quick Trick: BGE and BLT cover all cases; check logic carefully [OK]
Common Mistakes:
  • Assuming CMP needs SUBS
  • Misinterpreting flag meanings
  • Using overlapping branch conditions incorrectly

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