Vyper

Vyper Compiler Skill

Overview

Vyper is a Pythonic smart contract language for the EVM. The Vyper compiler transforms source code into EVM bytecode. In Ivy's differential fuzzing, we compare the compiled bytecode execution (via Boa) against Ivy's direct AST interpretation to find compiler bugs.

Installation

Vyper is already installed in the project's venv/. Always activate before use:

source venv/bin/activate

Reading Vyper Source Code

The Vyper compiler source is installed in the venv. To inspect it:

# Find vyper installation path
python -c "import vyper; print(vyper.__file__)"

# Typically at: venv/lib/python3.x/site-packages/vyper/

Key modules to understand:

• vyper/ast/ - AST node definitions and parsing
• vyper/semantics/ - Type system and semantic analysis
• vyper/codegen/ - IR and bytecode generation
• vyper/compiler/ - Compilation pipeline

AST Structure

Vyper AST nodes are in vyper.ast.nodes. Key nodes:

from vyper.ast import nodes as ast

# Statement nodes
ast.Assign, ast.AnnAssign, ast.If, ast.For, ast.Return
ast.Assert, ast.Raise, ast.Pass, ast.Break, ast.Continue

# Expression nodes  
ast.BinOp, ast.Compare, ast.BoolOp, ast.UnaryOp
ast.Call, ast.Subscript, ast.Attribute
ast.Name, ast.Int, ast.Str, ast.Bytes

Type System

from vyper.semantics.types import (
    IntegerT,      # int128, int256, uint8, uint256, etc.
    BoolT,         # bool
    AddressT,      # address
    BytesT,        # Bytes[N]
    StringT,       # String[N]
    DArrayT,       # DynArray[T, N]
    SArrayT,       # T[N] (static array)
    HashMapT,      # HashMap[K, V]
    StructT,       # struct definitions
    TupleT,        # tuples
)

Compilation Pipeline

from vyper.compiler import compile_code
from vyper.compiler.phases import CompilerData

# Get compiler data (AST, types, etc.)
compiler_data = CompilerData(source_code)

# Access annotated AST
annotated_ast = compiler_data.vyper_module

# Compile to bytecode
output = compile_code(source_code, output_formats=["bytecode", "abi"])

Debugging Tips

• When a divergence occurs, check if it's a compiler codegen bug:
  • Compare the annotated AST against expected semantics
  • Check if the IR generation is correct
  • Verify bytecode matches IR intent
• Use vyper.compile_code(src, output_formats=["ir"]) to inspect IR
• The venom pipeline (experimental) may have different bugs than legacy