GATE CS 2025 Set 1 — Question 52

NAT+2 / -0MediumThree-Address CodeIntermediate Code GenerationCompiler DesignBasic Blocks & Flow GraphsCode Optimization

Compiler Design → Code Optimization → Basic Blocks & Flow Graphs

Last updated 5 September 2026

Question

Refer to the given 3-address code sequence. This code sequence is split into basic blocks. The number of basic blocks is________.

Correct answer 6 to 6 Solution To find the number of basic blocks, we first identify the 'leaders' in the code sequence: 1. The first instruction is a leader: 1001 . 2. Any instruction that is the target of a conditional or unconditional jump is a leader: Target of 'goto 1003' at 1009: 1003 . Target of 'goto 1002' at 1011: 1002 . Target of 'goto 1013' at 1017: 1013 . 3. Any instruction that immediately follows a conditional or unconditional jump is a leader: Follows 'if...goto 1003' at 1009: 1010 . Follows 'if...goto 1002' at 1011: 1012 . The sorted list of leaders is: 1001, 1002, 1003, 1010, 1012, 1013. Each leader starts a new basic block. Therefore, there are 6 basic blocks: Block 1: 1001 Block 2: 1002 Block 3: 1003 to 1009 Block 4: 1010 to 1011 Block 5: 1012 Block 6: 1013 to 1017 Turn this into a strength. Explore AI-powered practice and doubt support with Success Tracker.

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Correct answer 6 to 6 Solution To find the number of basic blocks, we first identify the 'leaders' in the code sequence: 1. The first instruction is a leader: 1001 . 2. Any instruction that is the target of a conditional or unconditional jump is a leader: Target of 'goto 1003' at 1009: 1003 . Target of 'goto 1002' at 1011: 1002 . Target of 'goto 1013' at 1017: 1013 . 3. Any instruction that immediately follows a conditional or unconditional jump is a leader: Follows 'if...goto 1003' at 1009: 1010 . Follows 'if...goto 1002' at 1011: 1012 . The sorted list of leaders is: 1001, 1002, 1003, 1010, 1012, 1013. Each leader starts a new basic block. Therefore, there are 6 basic blocks: Block 1: 1001 Block 2: 1002 Block 3: 1003 to 1009 Block 4: 1010 to 1011 Block 5: 1012 Block 6: 1013 to 1017

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