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Introduction
Do you know about a compiler that can compile its source code? These types of compilers are called Self-Compiling Compilers, and bootstrapping in compiler design helps us create these compilers.
In this article, we will learn about Bootstrapping in Compiler Design. Using the bootstrapping process, we will see its representation and build a cross-compiler. In the end, we will also discuss uses, advantages, and disadvantages of bootstrapping in compiler design.
Bootstrapping in Compiler Design
Bootstrapping is a self-compiling compiler, written in its source language, ensuring self-sufficiency and language evolution. A self-compiling compiler is written in a source programming language that it determines to compile. In simple terms, a self-compiling compiler compiles its source code. This compiled compiler can compile everything else and its future versions as well.
Representation of Compiler in Bootstrapping
In Bootstrapping, a compiler is represented by three languages:
Source Language (S) is the language that the compiler compiles.
Implementation Language (I) is the language that the compiler is written in.
Target Language (T) is the language generated by the compiler.
A T-diagram is used to represent these three languages.
The above T-diagram shows that for a compiler with Source Language S and Target Language T, implemented with Implementation Language I, i.e., SIT.
Steps for Bootstrapping in Compiler Design
There are several steps involved in bootstrapping process for Compilers:
Select a high-level language for which the compiler has to be implemented, i.e., the target language. The language chosen should be capable and effective in generating quality code.
Implement the initial version of the compiler with the chosen high-level language. This initial version of the compiler should be capable of generating a partially functional code of the target language. This initial version is known as the stage 0 compiler.
Rather than directly generating the machine code, an intermediate compiler representation should be made. The Bootstrap compiler should be extended to create an Intermediate Representation.
Perform some optimizations on the bootstrapped compiler and use this compiler to compile its source code. The output is called a stage 1 compiler.
Test the stage 1 compiler and iterate the same process using the stage 1 compiler to compile its source code, leading to a newer version of the compiler called the stage 2 compiler. The same process can be repeated multiple times, leading to a more complex and advanced compiler version.
Cross Compilers in Bootstrapping
A cross-compiler is a compiler that creates executable code for a platform other than the one on which it is running. At the same time, bootstrapping is using a simple version of the compiler to compile a complex version of the same compiler.
Cross-Compilers in bootstrapping are used to compile the further and advanced versions of the compiler. With the help of a cross-compiler, we can generate executable code for the target platform without depending on the source compiler that runs directly on that platform.
A cross compiler for a source language ‘C,’ using implementation language ‘N’ and producing a target code for machine ‘S,’ is represented as CNS.
A cross compiler for a source language ‘N,’ using implementation language ‘M’ and generating code for machine ‘M,’ is represented by NMM.
A cross compiler for a source language ‘C,’ using implementation language ‘M’ and generating code for machine ‘S,’ is represented by CMS.
Using bootstrapping, the first two cross Compilers (CNS and NMM) can generate the third compiler (CMS).
CNS + NMM -> CMS
Creating a Cross-Compiler using Bootstrapping
Let’s create our own cross-compiler with the help of a compiler that has source language ‘D’ intermediate language ‘O’, and target language ‘O’ using a compiler that runs on source language ‘D’ with intermediate language ‘D’ and target language ‘T.’
Step-1: Start with writing the compiler representation for both compilers.
The source cross-compiler can be represented as DDT.
The intermediate cross-compiler can be represented as DOO.
Step-2: Create T-diagrams for both the cross compilers.
T-diagram for DDT :
T-diagram for DOO :
Step-3: Compiling the intermediate compiler with the source compiler we get.
DDT + DOO -> DOT
Step-4: Finally, we have got a cross compiler written in O language, which compiles D language and generates code in T language.
Example of Bootstrapped Compilers
There are many bootstrapped compilers in real-life scenarios like:
GCC (GNU Compiler): C, C++, and Fortran are the programming languages compiled by the GCC compiler. The earliest version of GCC used a simple C compiler. With time, GCC has become a self-compiling compiler that can compile its source code. GCC evolved and supported more languages with the help of the bootstrapping process.
Python: The C implementation of Python, or CPython, is a popular programming language. The earlier versions used C programming language for their implementation, and then it boosted its performance using bootstrapping with the help of an existing C compiler.
LLVM (Low-Level Virtual Machine): It is a compiler infrastructure that provides reusable components for building compilers. With the help of bootstrapping, LLVM evolved and is now capable of compiling its source code.
Uses of Bootstrapping
There are various uses of Bootstrapping in compiler design which are as follows:
It helps in creating new compilers from the actual ones.
It helps in the creation of new programming languages.
It helps in adding new features to compilers and programming languages.
It also helps in optimizing the compilers.
Advantages of Bootstrapping
Below are the advantages of bootstrapping in compiler design.
A significant advantage of bootstrapping is that it verifies that the compiler is compatible with the language it is written in. Since the compiler is written in the same language, it can understand the syntax and semantics of the language.
It allows code generation and compiler optimization. Bootstrapping allows greater control over the code generation process and makes it much easier.
Compiler development can be performed with higher-level language which is being compiled.
Disadvantages of Bootstrapping
Below are the disadvantages of bootstrapping in compiler design.
For complex languages or compilers, bootstrapping is a time-consuming process.
It requires much planning and execution to get positive and effective results.
Debugging in bootstrapping can be challenging as any errors would affect the further versions of the compiler.
A minimal version of the compiler written in a different language is required. This may lead to compatibility issues with the languages used.
What is the difference between bootstrapping and cross-compiler?
Bootstrapping is the process of building a self-compiling compiler that is written in a source programming language that it determines to compile. On the other hand, a cross-compiler is a compiler that runs on one platform but generates executable code for a different platform.
How are Compilers represented in Bootstrapping?
In Bootstrapping, a compiler is represented by three languages, namely Source Language(S), Intermediate Language(I), and Target Language(T). A T-diagram or SIT is used to represent the compiler.
What are Cross-Compilers?
A cross-compiler creates executable code for a platform other than the one on which it is running. For example, a cross-compiler running on a machine using C programming language can produce executable code for a machine using Java programming language.
Is Bootstrap really useful?
Yes, bootstrapping is highly useful in statistics and machine learning. It provides robust estimates of uncertainty, particularly when analytical methods are impractical or assumptions are violated, making it invaluable in various data analysis tasks.
Conclusion
In this article, we have discussed Bootstrapping in Compiler Design. Bootstrapping plays a crucial role in compiler design, offering a systematic approach to building compilers that are robust, extensible, and maintainable. By implementing a compiler in the same language it compiles, bootstrapping ensures self-sufficiency and enhances the compiler's reliability.
To learn more about compilers, you can refer to the below-mentioned articles:
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