Compiler Design Expert

Before Starting

1. Which compilation phase?
2. New language or existing compiler modification?
3. Optimization or correctness focus?

Core Expertise Areas

Lexical Analysis

Tokens: atomic units — keywords, identifiers, literals, operators. Regular expressions: define token patterns. Finite automata: DFA and NFA implement lexers. Lexer generators: Lex, Flex, ANTLR — generate lexer from token rules.

Parsing

Context-free grammars: productions defining language syntax. Top-down: recursive descent, LL parsers — predictive, left-to-right. Bottom-up: LR parsers — shift-reduce, more powerful, handles more grammars. Parser generators: Yacc, Bison, ANTLR — generate parser from grammar. Parse tree vs AST: AST removes redundant nodes, better for analysis.

Semantic Analysis

Type checking: static vs dynamic typing, type inference. Symbol table: scope management, variable binding, type lookup. Attribute grammars: synthesized and inherited attributes on parse tree. Name resolution: binding identifiers to declarations.

Intermediate Representation

Three-address code: at most three operands per instruction. SSA form: single static assignment, each variable defined exactly once. LLVM IR: typed, SSA-based, platform-independent, widely used. Control flow graph: basic blocks connected by edges.

Optimization

Constant folding: evaluate constant expressions at compile time. Dead code elimination: remove unreachable or unused code. Common subexpression elimination: compute repeated expressions once. Loop optimizations: unrolling, invariant code motion, vectorization. Inlining: replace function call with function body.

Code Generation

Instruction selection: map IR to target instructions. Register allocation: map variables to physical registers, spill to stack. Instruction scheduling: reorder instructions to minimize pipeline stalls.

Best Practices

• Separate phases clearly for maintainability
• Use SSA form for most optimization passes
• Test with both valid and invalid input programs
• Profile optimization passes on real workloads

Common Pitfalls

Pitfall	Fix
Shift-reduce conflicts	Refactor grammar or use precedence declarations
Missing phi nodes in SSA	Compute dominance frontiers correctly
Unsafe optimizations	Prove correctness of each transformation
Register spill storm	Improve register allocator or reduce register pressure

Related Skills

• compiler-expert
• algorithms-cs-expert
• computer-architecture-expert