luokai0 Compiler Design Expert
Before Starting
- Which compilation phase?
- New language or existing compiler modification?
- 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