Dropping sections of code that can never be reached or whose outputs are never read by the program. Code Generation Challenges
Type checking, type casting, and semantic errors versus syntactic errors. 4. Intermediate Code Generation (ICG)
Maps the optimized intermediate code to the actual target machine language or assembly code. It handles register allocation and assignment.
Uses a separate pointer array to list the execution sequence of the triples, decoupling structure from memory layout. 7. Code Optimization and Target Code Generation
Study Theory of Computation (TOC) before Compiler Design. Concepts of Regular Languages and CFGs are directly applied here.
┌───────────────┐ │ Parsers │ └───────┬───────┘ │ ┌─────────────────┴─────────────────┐ ▼ ▼ ┌───────────────────────┐ ┌───────────────────────┐ │ Top-Down Parsers │ │ Bottom-Up Parsers │ └───────────┬───────────┘ └───────────┬───────────┘ │ │ ┌─────┴─────┐ ┌─────┴─────┐ ▼ ▼ ▼ ▼ [ LL(1) ] [ Recursive [ LR(0) ] [ SLR(1) ] Descent ] ▼ ▼ [ LALR(1) ] [ CLR(1) ] 1. Top-Down Parsers
Three-Address Code (Quadruples, Triples, Indirect Triples), Postfix notation, and Syntax-Directed Translation (SDT) using S-attributed and L-attributed definitions. 5. Code Optimization
Checking grammar using Context-Free Grammars (CFG) and building a Parse Tree .
“Lexi Sings Silly Intermediate Optimized Code” (Lexical → Syntax → Semantic → Intermediate → Optimized → Code gen)
Watch out for "trick" questions counting the number of tokens in a snippet of C code. Remember that keywords, identifiers, constants, operators, and punctuation marks count as separate tokens. 2. Syntax Analysis (Parser)
GATE frequently tests your ability to find the minimal number of states required to construct a DFA for a given token pattern.
Do not start Compiler Design without a solid grasp of Regular Expressions and Context-Free Grammars from the Theory of Computation syllabus.
if (condition) x = a; else x = b;
For complex parsing questions, quickly test options using small, edge-case strings to eliminate incorrect grammar selections without building full parsing tables.
Ambiguity in grammars, Left Recursion, Left Factoring, and parsing techniques (LL, LR, SLR, LALR, CLR). 3. Semantic Analysis
A compiler is a sophisticated software system designed to translate high-level programming languages into machine code, bridging the gap between human-readable code and hardware execution. In the context of GATE, the focus is not just on writing a compiler, but on understanding the that drive it. Why is it important?
This comprehensive guide breaks down the core phases of Compiler Design, maps out the critical topics you must master, and provides the exact preparation strategy used by top rankers to ace these questions. 1. Syllabus Overview and Weightage Analysis
When a compiler encounters an if statement, it traditionally generates a "gate"—a binary decision point where the CPU must guess which way to go. When the CPU guesses wrong, it’s a disaster. The pipeline stalls, instructions are flushed, and performance plummets.
