RISC-V Assembly Language Server & Support

A powerful, custom Language Server Protocol (LSP) and syntax highlighter for RISC-V assembly code (.s, .asm, .S).

Provides a couple additional features over a standard syntax highlighter. The main features are the tracking of stack usage and label defintions. This was created with the bennett assembler in mind

Features

Intelligent Diagnostics (LSP)

• Undefined Label Detection: Instantly flags jumps (j, jal), branches (beq, bne, etc.), and address loads (la) that reference labels that don't exist.
• Duplicate Label Prevention: Throws an error if you try to define the same function or data label twice.
• Stack Tracking: Prevents standard assembly memory leaks.
  • Tracks mathematical stack offsets (addi sp, sp, -8 / subi sp, sp, 8).
  • Tracks exact register pushes and pops (e.g., sw t0, [sp] and lw t0, [sp]).
  • Warns you on ret if the stack pointer is unbalanced or if a specific register was left abandoned on the stack.
• Memory Alignment Checks: Warns you if word (lw/sw) or half-word (lh/sh) operations are using

Syntax Highlighting

• Full TextMate grammar support for the RISC-V base instruction set and standard pseudoinstructions.
• Smart Label Parsing: Supports both standard GNU syntax (main:) and colon-less labels (main).
• Rich coloring for strings ("text"), characters ('A'), hex literals (0x1F), decimals, and hardware registers.

Bennett Assembler Directives

Built-in support for custom data allocation directives:

• defw (Define Word) and defb (Define Byte).
• Full parsing of complex mathematical expressions for data allocation.
• Example: label_n defw (label_1 - label_2) * (label_3 / 4) (The LSP actively verifies that label_1, label_2, and label_3 exist in your document).

Quality of Life

• Smart Commenting: Press Cmd + / (Mac) or Ctrl + / (Windows) to instantly toggle standard ; line comments.
• Auto-closing: Automatically pairs brackets (), [], {}, and quotes.
• Go-To-Definition Cmd + <click> (Mac) or Ctrl + <click>(Windows) to go to definition of a label

Usage

Simply open any .s, .asm, or .S file. Ensure the Language Mode in the bottom right corner of VS Code is set to RISC-V.

The Language Server will automatically spin up in the background and begin analyzing your code as you type.

Example: Stack Tracking in Action

my_function:
    addi sp, sp, -8
    sw t0, [sp]       # LSP registers t0 as pushed
    
    lw t0, [sp]       # LSP registers t0 as popped
    lw t1, [sp]       # WARNING: t1 popped more than pushed!
    
    ret               # WARNING: sp offset is -8 at return!

Development & Contributing

This extension is built with standard VS Code Extension APIs and TypeScript.

Running locally

1. Clone this repository
2. Run npm install
3. Open the project in VS Code and press F5 to launch the Extension Development Host.

Testing

If you are planning on contributing, it is a good idea to make sure that any changes still pass all the tests in the test suite. The CI will run all tests on a push/pull request.

To run the tests locally

npm run test