AST Optimizers

Intro

An AST optimizer rewrites the Abstract Syntax Tree (AST) of a Python module to produce a more efficient code.

Currently in CPython 3.5, only basic optimizations are implemented by rewriting the bytecode: CPython peephole optimizer.

Old AST optimizer project

See old AST optimizer.

fatoptimizer

fatoptimizer project: AST optimizer implementing multiple optimizations and can specialize functions using guards of the fat module.

pythran AST

pythran.analysis.PureFunctions of pythran project, depend on ArgumentEffects and GlobalEffects analysis: automatically detect pure functions.

PyPy AST optimizer

https://bitbucket.org/pypy/pypy/src/default/pypy/interpreter/astcompiler/optimize.py

Cython AST optimizer

https://mail.python.org/pipermail/python-dev/2012-August/121300.html

• Compiler/Optimize.py
• Compiler/ParseTreeTransforms.py
• Compiler/Builtin.py
• Compiler/Pipeline.py

Links

CPython issues

• Issue #2181: optimize out local variables at end of function
• Issue #2499: Fold unary + and not on constants
• Issue #4264: Patch: optimize code to use LIST_APPEND instead of calling list.append
• Issue #7682: Optimisation of if with constant expression
• Issue #11549: Build-out an AST optimizer, moving some functionality out of the peephole optimizer
• Issue #17068: peephole optimization for constant strings
• Issue #17430: missed peephole optimization

AST

• instrumenting_the_ast.html
• the-internals-of-python-generator-functions-in-the-ast
• tlee-ast-optimize branch
• ast-optimization-branch-elimination-in-generator-functions