BEAM as a target

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compilation to BEAM bytecode, BEAM specific features like processes and messages

implement backend yourself and make a library out of it?

[jkenda]

Targeting BEAM through an IR

There are a few approaches to targeting the BEAM VM. One notable approach is seen in the development of the Gleam language. Although the current version of Gleam compiles to regular Erlang source code, a previous version compiled directly to BEAM bytecode via Core Erlang, which is an intermediate representation within the Erlang compiler. Core Erlang serves as a lower-level representation that can be more directly translated to BEAM bytecode.

For your needs, targeting Core Erlang might be a viable strategy to compile to BEAM bytecode, given its closer alignment with the BEAM's operational model compared to higher-level Erlang code. This approach could involve:

1. Translating Prefix Notation to Core Erlang: Develop a transformation process from your AST to Core Erlang, focusing on translating your language's constructs into their Core Erlang equivalents. Since Core Erlang is more granular and closer to BEAM bytecode, this step would involve detailed mapping of operations, control structures, and data handling.

2. Compiling Core Erlang to BEAM Bytecode: Leverage the existing Erlang compiler to compile the generated Core Erlang code into BEAM bytecode. This step benefits from the optimizations and stability of the Erlang compiler, ensuring that your code runs efficiently on the BEAM VM.

This strategy allows you to focus on the transformation from your language's abstract representation to Core Erlang, relying on the robust Erlang ecosystem to handle the final step of bytecode generation.

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Building BEAM bytecode directly

Building BEAM bytecode directly, bypassing the step of outputting to Erlang (or Core Erlang) and using the Erlang compiler, involves a deeper understanding of the BEAM VM's internals and bytecode specification. This process requires several key steps and considerations:

1. Understand BEAM Bytecode

• Specification: Familiarize yourself with the BEAM VM's bytecode specification, including instruction sets, data types, and execution model. Documentation, VM source code, and resources from the Erlang community can be invaluable here.
• Virtual Machine Architecture: Gain a deep understanding of how the BEAM VM operates, including its stack and heap management, process model, and how it handles concurrency and message passing.

2. Design Your Compiler Backend

• Instruction Mapping: Map your language's constructs (control flow, data manipulation, functions, etc.) to the corresponding BEAM instructions. This requires a detailed mapping process to ensure the semantics of your language are preserved in the bytecode.
• Type System: Design how your language's type system will be represented on the BEAM VM, considering Erlang's dynamic typing and pattern matching capabilities.
• Concurrency Model: If your language supports concurrency, align its model with BEAM's process-based concurrency, ensuring efficient use of BEAM's lightweight processes and message passing.

3. Implement the Bytecode Generator

• Bytecode Generation: Develop the component of your compiler that takes the AST (or another intermediate representation) and generates BEAM bytecode. This involves translating high-level constructs into low-level bytecode instructions.
• Optimization: Implement optimizations suitable for the BEAM VM's execution model, such as tail call optimization, to improve the efficiency of the generated bytecode.

4. Testing and Compatibility

• VM Compatibility: Test the generated bytecode extensively on the BEAM VM to ensure compatibility and to identify any runtime issues, such as crashes or performance bottlenecks.
• Erlang Interoperability: If desired, ensure that the generated modules can interoperate with Erlang and Elixir code, leveraging the rich ecosystem of libraries and tools available.

5. Tooling and Ecosystem Integration

• Build Tools: Create or integrate with existing build tools to streamline the process of compiling your language to BEAM bytecode and running it on the BEAM VM.
• Debugging and Profiling: Develop or integrate tools for debugging and profiling your language's code running on the BEAM VM, which is crucial for real-world usage.

Challenges

• Documentation and Resources: BEAM's bytecode specification and internal documentation may be limited, requiring reverse engineering or deep diving into VM source code.
• Complexity: Directly generating BEAM bytecode bypasses the optimizations and checks provided by the Erlang compiler, increasing the complexity of your compiler's backend.

Directly compiling to BEAM bytecode offers the potential for tight integration and optimization for the BEAM VM but comes with significant complexity and effort. Leveraging the existing Erlang ecosystem as a starting point can provide a more manageable path to running your language on the BEAM VM, with the option to explore direct bytecode generation as your language and compiler mature.