tags: Compiler Design

Lec1: Overview

Two Parts of a Compiler

1. Analysis(分析) part

• Front end of the compiler
• Divide the source program(High-level language)
• Generate an Intermediate Representation(IR，中間語言)

2. Synthesis(合成) part

• Back end of the compiler
• Generate the desire target program

6 Phases of the Compiler

Intermediate Code Generation In Compiler Design Notes

1. Lexical analysis(字典、辭彙分析)

2. Syntax analysis(語法、句法分析)

3. Semantic analysis(語意分析)

4. Intermediate code generation(4,5階段間IR產生)

5. Code optimization(最佳化)

6. Code generation(產生target language)

1st Phase: Lexical Analysis(辭彙分析)，Scanning

• 同義詞: analysis/ scanning/ lexing/ tokenization(把string 切為 tokens)
• 定義: Look words up in the dictionary. 需要檢查有無存在於字典(Dictionary)內

in Analogy to English	Syntax Analysis Example

• Examlpe
  

由範例可知，Lexical主旨在"Tokenize"，我們可以將position的公式對照Symbol Table(符號表)切分為對應<id,1> <=> <id,2> <+> <id,3> <＊> <60>，其中id為identifier(辨認字)的縮寫

2nd Phase: Syntax analysis(語法分析)，Parsing

• 同義詞: Parsing(剖析)
• 定義: Check if youre words do compose(組成) a sentence, find out the grammatically incorrect(文法錯誤)

in Analogy to English	Syntax Analysis Example

• Example
  

我們以能建出"Syntax Tree"，作為符合文法的

3rd Phase: Semantic analysis(語意分析)

• 定義: To understand the "meaning" of a sentence
• 包含: Type checking，將錯誤的型別(Ex: int->float)作"Type Conversion"

4th Phase: Intermediate Code Generation

• A low-level IR will has following characters:
  • Easy to product from syntax tree
  • Easy to translate into the target assembly code
• use three-adress code
  

5th Phase: Code Optimization

• 優化:用更短的程式碼跑得更快
• Often takes the most of the compilation time

6th Phase: Code Generation

• 定義:轉為對應target language

Whole Picture，(6 Phases整體關聯圖)