VCB — Vayu Compiler Backend

   

Vayu Compiler Backend

A compact, fast, Vayu-first C++20 backend for native machine code generation.

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Identity

VCB is the backend for Vayu.
.vyu is Vayu source.
.vcbir is VCB's internal IR.

VCB transforms the compiler representation produced by Vayu into native machine code.

  →  

Compiler Boundary

Vayu Source (.vyu)
        │
        ▼
Vayu Compiler / Frontend
        │
        ▼
VCBIR (.vcbir)
        │
        ▼
VCB
        │
        ▼
Native Machine Code

VCB does not parse .vyu directly. The Vayu frontend produces .vcbir, which VCB consumes.

VCBIR

VCBIR is VCB's typed, SSA-based internal intermediate representation.

It provides the boundary between the Vayu compiler and backend and represents:

• SSA values and basic blocks
• Phi nodes
• Calls and branches
• Loads and stores
• Integer and floating-point operations
• Explicit conversions

VCBIR is an internal compiler representation, not another programming language.

Backend

VCB is written in C++20 and contains the backend pipeline for:

• Analysis
• Optimization
• Lowering
• Register allocation
• Instruction selection
• Peephole optimization
• Native code generation

VCB takes inspiration from compact backend architectures such as QBE, while Vayu remains its language target.

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Why I Am Making VCB

VCB exists to give Vayu its own compact native backend instead of depending on a large external compiler framework.

Goal	Reason
Vayu-first	Built around Vayu's own compiler requirements
Fast	Keep the compilation path short and lightweight
Compact	Make the backend understandable and maintainable
Native	Generate machine code directly from VCBIR
Independent	Avoid making Vayu depend on another backend
Experimental	Keep backend development easy to change and test

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VCBIR Example

export function i32 main() {
entry:
    %1 = add i32 5, 3
    %2 = mul i32 %1, 2
    ret i32 %2
}

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Testing

Tests are kept under tests/ and cover the current backend source:

tests/
├── arith.vcb
├── bitwise.vcb
├── branch.vcb
├── call.vcb
├── coalesce.vcb
├── compare.vcb
├── conv.vcb
├── dense.vcb
├── loop.vcb
├── peephole.vcb
├── smoke.vcb
└── symbolic.vcb

The test suite covers arithmetic, bitwise operations, branches, calls, comparisons, conversions, loops, register coalescing, dense control flow, peephole optimization, symbolic handling, and smoke tests.

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Building

Build, CMake, compiler, Visual Studio, testing, and troubleshooting instructions are maintained in:

→ build.md

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Vayu + VCB

  ×  

.vyu → Vayu Compiler → .vcbir → VCB → Native Machine Code

→ Vayu repository

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What VCB Is Not

• Not a frontend — Vayu handles .vyu parsing.
• Not a generic backend — VCB is built for Vayu.
• Not LLVM/GCC — it intentionally has a much smaller scope.
• Not another language — VCBIR is an internal compiler representation.

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Contributing

Contributions are welcome in:

• VCBIR
• Backend optimization
• Analysis and SSA
• Register allocation
• Instruction selection
• x86-64 code generation
• Tests
• Vayu integration

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License

VCB is released under the Apache License 2.0.

LICENSE

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VCB

A compact native backend for Vayu.