Compilers

Introduction #

A compiler is a software tool that translates source code written in a high-level programming language (like C, C++, or Java) into low-level code (such as assembly or machine code) that can be executed by a target processor or embedded system. The compilation process involves several stages, each performing a specific task to ensure the correct and efficient translation of the source code.

An overview of the compilation process #

  1. Lexical Analysis: The compiler reads the source code and breaks it down into tokens (keywords, identifiers, literals, operators, etc.). This phase is handled by a component called the lexer or scanner.

  2. Syntax Analysis: The compiler checks the tokens’ arrangement against the rules of the programming language’s grammar. This phase involves the construction of a parse tree to represent the program’s hierarchical structure. The component responsible for this is called the parser.

  3. Semantic Analysis: The compiler checks for any semantic errors, such as type mismatches, undeclared variables, or incorrect function calls. In this phase, the parse tree is often annotated with additional information to facilitate further processing.

  4. Intermediate Code Generation: The compiler converts the annotated parse tree into an intermediate representation (IR) that is easier to manipulate and optimize. Common IR forms include three-address code, static single assignment (SSA), or a control-flow graph.

  5. Code Optimization: The compiler applies various optimization techniques to the intermediate code to improve the generated code’s efficiency, such as constant folding, dead code elimination, or loop unrolling. This phase is crucial for embedded systems where resources are limited.

  6. Target Code Generation: The compiler translates the optimized intermediate code into the target machine code or assembly language. This phase also involves register allocation and instruction scheduling to generate efficient code for the target processor.

  7. Linking: The compiler links the generated machine code with libraries and other object files to create an executable binary.

An example of a popular compiler in the embedded systems domain is the GNU Compiler Collection (GCC). It supports various languages and target architectures, making it a versatile choice for embedded systems development.