mirror of https://github.com/python/cpython.git
GH-125498: Update JIT builds to use LLVM 19 and preserve_none (GH-125499)
This commit is contained in:
Savannah Ostrowski
GitHub
parent
597d814334
commit
c29bbe2101
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@ -61,7 +61,7 @@ jobs:
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- true
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- false
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llvm:
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- 18
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- 19
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include:
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- target: i686-pc-windows-msvc/msvc
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architecture: Win32
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@ -121,10 +121,15 @@ jobs:
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choco install llvm --allow-downgrade --no-progress --version ${{ matrix.llvm }}.1.0
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./PCbuild/build.bat --experimental-jit ${{ matrix.debug && '-d' || '' }} -p ${{ matrix.architecture }}
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# The `find` line is required as a result of https://github.com/actions/runner-images/issues/9966.
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# This is a bug in the macOS runner image where the pre-installed Python is installed in the same
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# directory as the Homebrew Python, which causes the build to fail for macos-13. This line removes
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# the symlink to the pre-installed Python so that the Homebrew Python is used instead.
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- name: Native macOS
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if: runner.os == 'macOS'
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run: |
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brew update
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find /usr/local/bin -lname '*/Library/Frameworks/Python.framework/*' -delete
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brew install llvm@${{ matrix.llvm }}
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SDKROOT="$(xcrun --show-sdk-path)" \
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./configure --enable-experimental-jit ${{ matrix.debug && '--with-pydebug' || '--enable-optimizations --with-lto' }}
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@ -165,6 +170,10 @@ jobs:
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name: Free-Threaded (Debug)
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needs: interpreter
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runs-on: ubuntu-latest
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strategy:
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matrix:
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llvm:
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- 19
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steps:
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- uses: actions/checkout@v4
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- uses: actions/setup-python@v5
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@ -172,8 +181,8 @@ jobs:
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python-version: '3.11'
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- name: Build with JIT enabled and GIL disabled
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run: |
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sudo bash -c "$(wget -O - https://apt.llvm.org/llvm.sh)" ./llvm.sh 18
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export PATH="$(llvm-config-18 --bindir):$PATH"
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sudo bash -c "$(wget -O - https://apt.llvm.org/llvm.sh)" ./llvm.sh ${{ matrix.llvm }}
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export PATH="$(llvm-config-${{ matrix.llvm }} --bindir):$PATH"
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./configure --enable-experimental-jit --with-pydebug --disable-gil
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make all --jobs 4
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- name: Run tests
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@ -0,0 +1 @@
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Update JIT compilation to use LLVM 19
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@ -0,0 +1,4 @@
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The JIT has been updated to leverage Clang 19’s new ``preserve_none`` attribute,
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which supports more platforms and is more useful than LLVM's existing ``ghccc``
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calling convention. This also removes the need to manually patch the calling
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convention in LLVM IR, simplifying the JIT compilation process.
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@ -7,49 +7,46 @@ ## Installing LLVM
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The JIT compiler does not require end users to install any third-party dependencies, but part of it must be *built* using LLVM[^why-llvm]. You are *not* required to build the rest of CPython using LLVM, or even the same version of LLVM (in fact, this is uncommon).
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LLVM version 18 is required. Both `clang` and `llvm-readobj` need to be installed and discoverable (version suffixes, like `clang-18`, are okay). It's highly recommended that you also have `llvm-objdump` available, since this allows the build script to dump human-readable assembly for the generated code.
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LLVM version 19 is required. Both `clang` and `llvm-readobj` need to be installed and discoverable (version suffixes, like `clang-19`, are okay). It's highly recommended that you also have `llvm-objdump` available, since this allows the build script to dump human-readable assembly for the generated code.
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It's easy to install all of the required tools:
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### Linux
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Install LLVM 18 on Ubuntu/Debian:
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Install LLVM 19 on Ubuntu/Debian:
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```sh
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wget https://apt.llvm.org/llvm.sh
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chmod +x llvm.sh
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sudo ./llvm.sh 18
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sudo ./llvm.sh 19
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```
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Install LLVM 18 on Fedora Linux 40 or newer:
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Install LLVM 19 on Fedora Linux 40 or newer:
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```sh
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sudo dnf install 'clang(major) = 18' 'llvm(major) = 18'
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sudo dnf install 'clang(major) = 19' 'llvm(major) = 19'
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```
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### macOS
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Install LLVM 18 with [Homebrew](https://brew.sh):
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Install LLVM 19 with [Homebrew](https://brew.sh):
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```sh
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brew install llvm@18
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brew install llvm@19
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```
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Homebrew won't add any of the tools to your `$PATH`. That's okay; the build script knows how to find them.
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### Windows
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Install LLVM 18 [by searching for it on LLVM's GitHub releases page](https://github.com/llvm/llvm-project/releases?q=18), clicking on "Assets", downloading the appropriate Windows installer for your platform (likely the file ending with `-win64.exe`), and running it. **When installing, be sure to select the option labeled "Add LLVM to the system PATH".**
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Install LLVM 19 [by searching for it on LLVM's GitHub releases page](https://github.com/llvm/llvm-project/releases?q=19), clicking on "Assets", downloading the appropriate Windows installer for your platform (likely the file ending with `-win64.exe`), and running it. **When installing, be sure to select the option labeled "Add LLVM to the system PATH".**
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Alternatively, you can use [chocolatey](https://chocolatey.org):
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```sh
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choco install llvm --version=18.1.6
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choco install llvm --version=19.1.0
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```
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### Dev Containers
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If you are working CPython in a [Codespaces instance](https://devguide.python.org/getting-started/setup-building/#using-codespaces), there's no need to install LLVM as the Fedora 40 base image includes LLVM 18 out of the box.
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## Building
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@ -8,7 +8,7 @@
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import subprocess
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import typing
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_LLVM_VERSION = 18
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_LLVM_VERSION = 19
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_LLVM_VERSION_PATTERN = re.compile(rf"version\s+{_LLVM_VERSION}\.\d+\.\d+\S*\s+")
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_P = typing.ParamSpec("_P")
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@ -2,6 +2,7 @@
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import dataclasses
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import enum
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import sys
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import typing
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import _schema
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@ -132,8 +133,18 @@ class Hole:
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def __post_init__(self) -> None:
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self.func = _PATCH_FUNCS[self.kind]
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def fold(self, other: typing.Self) -> typing.Self | None:
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def fold(self, other: typing.Self, body: bytes) -> typing.Self | None:
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"""Combine two holes into a single hole, if possible."""
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instruction_a = int.from_bytes(
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body[self.offset : self.offset + 4], byteorder=sys.byteorder
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)
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instruction_b = int.from_bytes(
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body[other.offset : other.offset + 4], byteorder=sys.byteorder
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)
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reg_a = instruction_a & 0b11111
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reg_b1 = instruction_b & 0b11111
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reg_b2 = (instruction_b >> 5) & 0b11111
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if (
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self.offset + 4 == other.offset
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and self.value == other.value
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@ -141,6 +152,7 @@ def fold(self, other: typing.Self) -> typing.Self | None:
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and self.addend == other.addend
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and self.func == "patch_aarch64_21rx"
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and other.func == "patch_aarch64_12x"
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and reg_a == reg_b1 == reg_b2
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):
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# These can *only* be properly relaxed when they appear together and
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# patch the same value:
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@ -26,7 +26,6 @@
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PYTHON_EXECUTOR_CASES_C_H = CPYTHON / "Python" / "executor_cases.c.h"
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TOOLS_JIT_TEMPLATE_C = TOOLS_JIT / "template.c"
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_S = typing.TypeVar("_S", _schema.COFFSection, _schema.ELFSection, _schema.MachOSection)
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_R = typing.TypeVar(
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"_R", _schema.COFFRelocation, _schema.ELFRelocation, _schema.MachORelocation
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@ -39,7 +38,6 @@ class _Target(typing.Generic[_S, _R]):
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_: dataclasses.KW_ONLY
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alignment: int = 1
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args: typing.Sequence[str] = ()
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ghccc: bool = False
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prefix: str = ""
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stable: bool = False
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debug: bool = False
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@ -88,11 +86,7 @@ async def _parse(self, path: pathlib.Path) -> _stencils.StencilGroup:
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sections: list[dict[typing.Literal["Section"], _S]] = json.loads(output)
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for wrapped_section in sections:
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self._handle_section(wrapped_section["Section"], group)
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# The trampoline's entry point is just named "_ENTRY", since on some
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# platforms we later assume that any function starting with "_JIT_" uses
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# the GHC calling convention:
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entry_symbol = "_JIT_ENTRY" if "_JIT_ENTRY" in group.symbols else "_ENTRY"
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assert group.symbols[entry_symbol] == (_stencils.HoleValue.CODE, 0)
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assert group.symbols["_JIT_ENTRY"] == (_stencils.HoleValue.CODE, 0)
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if group.data.body:
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line = f"0: {str(bytes(group.data.body)).removeprefix('b')}"
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group.data.disassembly.append(line)
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@ -112,9 +106,6 @@ def _handle_relocation(
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async def _compile(
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self, opname: str, c: pathlib.Path, tempdir: pathlib.Path
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) -> _stencils.StencilGroup:
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# "Compile" the trampoline to an empty stencil group if it's not needed:
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if opname == "trampoline" and not self.ghccc:
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return _stencils.StencilGroup()
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o = tempdir / f"{opname}.o"
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args = [
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f"--target={self.triple}",
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@ -128,6 +119,7 @@ async def _compile(
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f"-I{CPYTHON / 'Include' / 'internal'}",
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f"-I{CPYTHON / 'Include' / 'internal' / 'mimalloc'}",
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f"-I{CPYTHON / 'Python'}",
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f"-I{CPYTHON / 'Tools' / 'jit'}",
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"-O3",
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"-c",
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# This debug info isn't necessary, and bloats out the JIT'ed code.
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@ -143,44 +135,12 @@ async def _compile(
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# Don't call stack-smashing canaries that we can't find or patch:
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"-fno-stack-protector",
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"-std=c11",
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"-o",
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f"{o}",
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f"{c}",
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*self.args,
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]
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if self.ghccc:
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# This is a bit of an ugly workaround, but it makes the code much
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# smaller and faster, so it's worth it. We want to use the GHC
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# calling convention, but Clang doesn't support it. So, we *first*
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# compile the code to LLVM IR, perform some text replacements on the
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# IR to change the calling convention(!), and then compile *that*.
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# Once we have access to Clang 19, we can get rid of this and use
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# __attribute__((preserve_none)) directly in the C code instead:
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ll = tempdir / f"{opname}.ll"
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args_ll = args + [
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# -fomit-frame-pointer is necessary because the GHC calling
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# convention uses RBP to pass arguments:
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"-S",
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"-emit-llvm",
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"-fomit-frame-pointer",
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"-o",
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f"{ll}",
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f"{c}",
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]
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await _llvm.run("clang", args_ll, echo=self.verbose)
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ir = ll.read_text()
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# This handles declarations, definitions, and calls to named symbols
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# starting with "_JIT_":
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ir = re.sub(
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r"(((noalias|nonnull|noundef) )*ptr @_JIT_\w+\()", r"ghccc \1", ir
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)
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# This handles calls to anonymous callees, since anything with
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# "musttail" needs to use the same calling convention:
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ir = ir.replace("musttail call", "musttail call ghccc")
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# Sometimes *both* replacements happen at the same site, so fix it:
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ir = ir.replace("ghccc ghccc", "ghccc")
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ll.write_text(ir)
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args_o = args + ["-Wno-unused-command-line-argument", "-o", f"{o}", f"{ll}"]
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else:
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args_o = args + ["-o", f"{o}", f"{c}"]
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await _llvm.run("clang", args_o, echo=self.verbose)
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await _llvm.run("clang", args, echo=self.verbose)
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return await self._parse(o)
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async def _build_stencils(self) -> dict[str, _stencils.StencilGroup]:
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@ -519,7 +479,6 @@ def _handle_relocation(
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def get_target(host: str) -> _COFF | _ELF | _MachO:
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"""Build a _Target for the given host "triple" and options."""
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# ghccc currently crashes Clang when combined with musttail on aarch64. :(
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target: _COFF | _ELF | _MachO
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if re.fullmatch(r"aarch64-apple-darwin.*", host):
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target = _MachO(host, alignment=8, prefix="_")
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@ -535,16 +494,20 @@ def get_target(host: str) -> _COFF | _ELF | _MachO:
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]
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target = _ELF(host, alignment=8, args=args)
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elif re.fullmatch(r"i686-pc-windows-msvc", host):
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args = ["-DPy_NO_ENABLE_SHARED"]
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target = _COFF(host, args=args, ghccc=True, prefix="_")
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args = [
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"-DPy_NO_ENABLE_SHARED",
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# __attribute__((preserve_none)) is not supported
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"-Wno-ignored-attributes",
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]
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target = _COFF(host, args=args, prefix="_")
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elif re.fullmatch(r"x86_64-apple-darwin.*", host):
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target = _MachO(host, ghccc=True, prefix="_")
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target = _MachO(host, prefix="_")
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elif re.fullmatch(r"x86_64-pc-windows-msvc", host):
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args = ["-fms-runtime-lib=dll"]
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target = _COFF(host, args=args, ghccc=True)
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target = _COFF(host, args=args)
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elif re.fullmatch(r"x86_64-.*-linux-gnu", host):
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args = ["-fpic"]
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target = _ELF(host, args=args, ghccc=True)
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target = _ELF(host, args=args)
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else:
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raise ValueError(host)
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return target
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@ -65,7 +65,7 @@ def _dump_stencil(opname: str, group: _stencils.StencilGroup) -> typing.Iterator
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if skip:
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skip = False
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continue
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if pair and (folded := hole.fold(pair)):
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if pair and (folded := hole.fold(pair, stencil.body)):
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skip = True
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hole = folded
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yield f" {hole.as_c(part)}"
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@ -0,0 +1,4 @@
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// To use preserve_none in JIT builds, we need to declare a separate function
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// pointer with __attribute__((preserve_none)), since this attribute may not be
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// supported by the compiler used to build the rest of the interpreter.
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typedef jit_func __attribute__((preserve_none)) jit_func_preserve_none;
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@ -21,6 +21,8 @@
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#include "ceval_macros.h"
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#include "jit.h"
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#undef CURRENT_OPARG
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#define CURRENT_OPARG() (_oparg)
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@ -49,7 +51,7 @@
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do { \
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OPT_STAT_INC(traces_executed); \
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__attribute__((musttail)) \
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return ((jit_func)((EXECUTOR)->jit_side_entry))(frame, stack_pointer, tstate); \
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return ((jit_func_preserve_none)((EXECUTOR)->jit_side_entry))(frame, stack_pointer, tstate); \
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} while (0)
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#undef GOTO_TIER_ONE
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@ -72,7 +74,7 @@ do { \
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do { \
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PyAPI_DATA(void) ALIAS; \
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__attribute__((musttail)) \
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return ((jit_func)&ALIAS)(frame, stack_pointer, tstate); \
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return ((jit_func_preserve_none)&ALIAS)(frame, stack_pointer, tstate); \
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} while (0)
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#undef JUMP_TO_JUMP_TARGET
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@ -86,7 +88,7 @@ do { \
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#define TIER_TWO 2
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_Py_CODEUNIT *
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__attribute__((preserve_none)) _Py_CODEUNIT *
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_JIT_ENTRY(_PyInterpreterFrame *frame, _PyStackRef *stack_pointer, PyThreadState *tstate)
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{
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// Locals that the instruction implementations expect to exist:
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@ -4,11 +4,10 @@
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#include "pycore_frame.h"
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#include "pycore_jit.h"
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// This is where the calling convention changes, on platforms that require it.
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// The actual change is patched in while the JIT compiler is being built, in
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// Tools/jit/_targets.py. On other platforms, this function compiles to nothing.
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#include "jit.h"
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_Py_CODEUNIT *
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_ENTRY(_PyInterpreterFrame *frame, _PyStackRef *stack_pointer, PyThreadState *tstate)
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_JIT_ENTRY(_PyInterpreterFrame *frame, _PyStackRef *stack_pointer, PyThreadState *tstate)
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{
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// This is subtle. The actual trace will return to us once it exits, so we
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// need to make sure that we stay alive until then. If our trace side-exits
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@ -19,7 +18,7 @@ _ENTRY(_PyInterpreterFrame *frame, _PyStackRef *stack_pointer, PyThreadState *ts
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Py_INCREF(executor);
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// Note that this is *not* a tail call:
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PyAPI_DATA(void) _JIT_CONTINUE;
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_Py_CODEUNIT *target = ((jit_func)&_JIT_CONTINUE)(frame, stack_pointer, tstate);
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_Py_CODEUNIT *target = ((jit_func_preserve_none)&_JIT_CONTINUE)(frame, stack_pointer, tstate);
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Py_SETREF(tstate->previous_executor, executor);
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return target;
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}
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