feat: add Profile-Guided Optimization (PGO) support#3085
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Add `--pgo` CLI flag and `pgo-command` config in `[tool.maturin]` to enable PGO builds via a three-phase pipeline: 1. Build instrumented wheel with `-Cprofile-generate` 2. Install in temp venv and run the user's pgo-command to collect `.profraw` files 3. Merge profiles with `llvm-profdata` and rebuild with `-Cprofile-use` For non-abi3 PyO3 builds, each interpreter gets its own instrument-train-optimize cycle via `build_single_pyo3_wheel()`, since different Python versions produce different compiled code through PyO3's build-time configuration. For abi3/cffi/uniffi/bin builds, a single PGO pass suffices. Key components: - `PgoContext` in `src/pgo.rs`: manages temp dirs, `llvm-profdata` resolution, venv creation, dependency installation, and profile merging - `PgoPhase` enum injected into `BuildContext.pgo_phase`, read in `compile.rs` to add rustc flags - `clone_for_pgo()` helper to reduce context-setup boilerplate - `build_single_pyo3_wheel()` extracted from `build_pyo3_wheels()` to share the compile-audit-write pipeline with the PGO path
Use `uv venv` and `uv pip install` when uv is available, falling back to `python -m venv` and `python -m pip` otherwise. Detection reuses the existing `find_uv_python`/`find_uv_bin` helpers from the develop module. Extracted a `pip_install()` helper on `PgoContext` to avoid duplicating the uv-vs-pip dispatch across install calls.
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Pull request overview
Adds a first-class Profile-Guided Optimization (PGO) build mode to maturin, driven by a pgo-command configured in pyproject.toml, and wires it into the wheel build pipeline.
Changes:
- Introduce
--pgoCLI flag (build + publish) and plumb it intoBuildContext. - Add
[tool.maturin] pgo-commandconfig and implement a three-phase PGO build (instrument → train → optimize). - Inject rustc PGO flags during compilation and refactor PyO3 wheel building to support per-interpreter PGO cycles.
Reviewed changes
Copilot reviewed 8 out of 8 changed files in this pull request and generated 5 comments.
Show a summary per file
| File | Description |
|---|---|
| src/pyproject_toml.rs | Adds pgo-command to [tool.maturin] and exposes it via an accessor. |
| src/pgo.rs | New module implementing PGO orchestration (venv creation, workload execution, profile merge). |
| src/main.rs | Adds --pgo flag to build/publish commands and passes it into the build context builder. |
| src/lib.rs | Registers the new pgo module. |
| src/compile.rs | Injects -Cprofile-generate / -Cprofile-use rustflags based on the active PGO phase. |
| src/build_context/wheels.rs | Factors out a reusable “build a single PyO3 wheel” helper for PGO per-interpreter cycles. |
| src/build_context/mod.rs | Routes wheel building through PGO pipeline when enabled; implements single-pass + per-interpreter flows. |
| src/build_context/builder.rs | Adds builder flag for PGO and enforces presence of pgo-command when enabled. |
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1. Set `current_dir` to the project root when running the instrumentation command, so relative paths (e.g. `pytest tests/`) resolve correctly even when maturin is invoked from elsewhere. 2. Propagate `read_dir` entry errors in `merge_profiles()` instead of silently ignoring them, avoiding a misleading 'no .profraw files' error when files exist but can't be read. 3. In single-pass PGO, restrict Phase 1 to a single interpreter so we don't wastefully compile multiple instrumented wheels when only the first is used for training. 4. Reject empty/whitespace-only `pgo-command` at builder validation time rather than failing at runtime in `run_instrumentation`. 5. Add unit tests for `pgo-command` TOML deserialization (present and absent cases).
1. Set `current_dir` to the project root when running the instrumentation command, so relative paths (e.g. `pytest tests/`) resolve correctly even when maturin is invoked from elsewhere. 2. Propagate `read_dir` entry errors in `merge_profiles()` instead of silently ignoring them, avoiding a misleading 'no .profraw files' error when files exist but can't be read. 3. In single-pass PGO, restrict Phase 1 to a single interpreter so we don't wastefully compile multiple instrumented wheels when only the first is used for training. 4. Reject empty/whitespace-only `pgo-command` at builder validation time rather than failing at runtime in `run_instrumentation`. 5. Add unit tests for `pgo-command` TOML deserialization (present and absent cases).
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PyPy emits debug output to stdout when importing pyo3 modules, causing
check_installed to fail because the entire stdout didn't match 'SUCCESS'.
Check only the last line instead, which is where print('SUCCESS') lands.
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Add
--pgoCLI flag andpgo-commandconfig in[tool.maturin]to enable PGO builds via a three-phase pipeline:-Cprofile-generate.profrawfilesllvm-profdataand rebuild with-Cprofile-useFor non-abi3 PyO3 builds, each interpreter gets its own instrument-train-optimize cycle via
build_single_pyo3_wheel(), since different Python versions produce different compiled code through PyO3's build-time configuration. For abi3/cffi/uniffi/bin builds, a single PGO pass suffices.Key components:
PgoContextinsrc/pgo.rs: manages temp dirs,llvm-profdataresolution, venv creation, dependency installation, and profile mergingPgoPhaseenum injected intoBuildContext.pgo_phase, read incompile.rsto add rustc flagsclone_for_pgo()helper to reduce context-setup boilerplatebuild_single_pyo3_wheel()extracted frombuild_pyo3_wheels()to share the compile-audit-write pipeline with the PGO pathCloses #1840