Build a Compiler: A Comprehensive Guide
- This is a captivating excerpt from a blog post detailing the author's journey of reimplementing Jack Crenshaw's "Let's Build a Compiler" tutorial, but this time targeting WebAssembly (WASM).
- The author is rebuilding a compiler from scratch, following the classic "Let's Build a Compiler" tutorial, but instead of generating native code, the compiler outputs WASM.
- * By-Reference Parameter Handling: The code highlights the complexities of passing parameters by reference in WASM.
This is a captivating excerpt from a blog post detailing the author’s journey of reimplementing Jack Crenshaw’s “Let’s Build a Compiler” tutorial, but this time targeting WebAssembly (WASM). Here’s a breakdown of the key takeaways and insights:
Core Idea:
The author is rebuilding a compiler from scratch, following the classic “Let’s Build a Compiler” tutorial, but instead of generating native code, the compiler outputs WASM. This is a great exercise for understanding both compiler design and the WASM virtual machine.
Key Observations about the Generated WASM:
* By-Reference Parameter Handling: The code highlights the complexities of passing parameters by reference in WASM. The author’s previous blog post (linked) delves deeper into this. Essentially,WASM requires explicit stack manipulation to pass addresses of variables.
* Lack of optimization: The generated WASM code is intentionally unoptimized. The focus is on correctness and clarity, not performance. This makes it easier to understand the direct translation of the compiler’s logic into WASM instructions.
* Implicit Return via Global Variable: the global variable X is used as an implicit return value. This is a testing convenience for the author’s compiler, allowing for easy verification of results. It’s not a standard practice,but simplifies testing.
* Stack Management: The code demonstrates how the stack pointer ($__sp) is used to allocate space for parameters and local variables. this is crucial for understanding how WASM functions operate.
* i32.store and i32.load: These instructions are used to store and load values from memory, specifically in relation to the by-reference parameter.
What Makes the Original Tutorial Special:
The author reflects on why Crenshaw’s tutorial is so effective:
* Conversational style: Crenshaw’s writing is clear and engaging.
* Step-by-Step Recursive Descent Parser: The tutorial builds a parser incrementally, which is a more approachable method than starting with complex parser generators (like lex and yacc).
* Shift in Perspective: The tutorial encouraged the author to embrace hand-written recursive descent parsers, which became their preferred approach.
In essence, this excerpt showcases a practical and insightful project that combines classic compiler design principles with modern web technologies (WASM). It’s a valuable resource for anyone interested in learning about compilers, WASM, or both.