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Merged
savannahostrowski merged 15 commits into from
Nov 12, 2025
Merged

GH-140479: Update JIT builds to use LLVM 21 #140973

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7e7ebaf
Initial commit for LLVM 21
savannahostrowski Nov 3, 2025
ae4a01d
Update CI
savannahostrowski Nov 3, 2025
da9b795
Another CI fix
savannahostrowski Nov 3, 2025
d079df9
Add debugging
savannahostrowski Nov 4, 2025
322ea9b
Add fix for exe
savannahostrowski Nov 4, 2025
27a91ac
Update tarball extraction
savannahostrowski Nov 4, 2025
2ca8603
Fix for windows
savannahostrowski Nov 4, 2025
39e1339
Clean up after debugging
savannahostrowski Nov 4, 2025
38105ce
Uncomment CI
savannahostrowski Nov 4, 2025
e85c8f8
📜🤖 Added by blurb_it.
blurb-it[bot] Nov 4, 2025
3ca9733
Fix README
savannahostrowski Nov 4, 2025
4508fc5
Merge branch 'llvm-21' of https://github.com/savannahostrowski/cpytho…
savannahostrowski Nov 4, 2025
ef52c5a
Remove fixes for Windows release artifacts
savannahostrowski Nov 4, 2025
9778bdd
Merge branch 'main' into llvm-21
savannahostrowski Nov 6, 2025
39438c0
Merge branch 'main' into llvm-21
savannahostrowski Nov 12, 2025
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8 changes: 4 additions & 4 deletions .github/workflows/jit.yml
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Original file line numberDiff line numberDiff line change
Expand Up@@ -68,7 +68,7 @@ jobs:
- true
- false
llvm:
- 20
- 21
include:
- target: i686-pc-windows-msvc/msvc
architecture: Win32
Expand DownExpand Up@@ -138,7 +138,7 @@ jobs:
fail-fast: false
matrix:
llvm:
- 20
- 21
steps:
- uses: actions/checkout@v4
with:
Expand DownExpand Up@@ -166,7 +166,7 @@ jobs:
fail-fast: false
matrix:
llvm:
- 20
- 21
steps:
- uses: actions/checkout@v4
with:
Expand All@@ -193,7 +193,7 @@ jobs:
fail-fast: false
matrix:
llvm:
- 20
- 21
steps:
- uses: actions/checkout@v4
with:
Expand Down
1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2025-11-04-04-57-24.gh-issue-140479.lwQ2v2.rst
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@@ -0,0 +1 @@
Update JIT compilation to use LLVM 21 at build time.
4 changes: 2 additions & 2 deletions PCbuild/get_externals.bat
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Expand Up@@ -82,7 +82,7 @@ if NOT "%IncludeLibffi%"=="false" set binaries=%binaries% libffi-3.4.4
if NOT "%IncludeSSL%"=="false" set binaries=%binaries% openssl-bin-3.0.18
if NOT "%IncludeTkinter%"=="false" set binaries=%binaries% tcltk-8.6.15.0
if NOT "%IncludeSSLSrc%"=="false" set binaries=%binaries% nasm-2.11.06
if NOT "%IncludeLLVM%"=="false" set binaries=%binaries% llvm-20.1.8.0
if NOT "%IncludeLLVM%"=="false" set binaries=%binaries% llvm-21.1.4.0

for %%b in (%binaries%) do (
if exist "%EXTERNALS_DIR%\%%b" (
Expand All@@ -92,7 +92,7 @@ for %%b in (%binaries%) do (
git clone --depth 1 https://github.com/%ORG%/cpython-bin-deps --branch %%b "%EXTERNALS_DIR%\%%b"
) else (
echo.Fetching %%b...
if "%%b"=="llvm-20.1.8.0" (
if "%%b"=="llvm-21.1.4.0" (
%PYTHON% -E "%PCBUILD%\get_external.py" --release --organization %ORG% --externals-dir "%EXTERNALS_DIR%" %%b
) else (
%PYTHON% -E "%PCBUILD%\get_external.py" --binary --organization %ORG% --externals-dir "%EXTERNALS_DIR%" %%b
Expand Down
20 changes: 10 additions & 10 deletions Tools/jit/README.md
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Expand Up@@ -9,32 +9,32 @@ Python 3.11 or newer is required to build the JIT.

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).

LLVM version 20 is the officially supported version. You can modify if needed using the `LLVM_VERSION` env var during configure. 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.
LLVM version 21 is the officially supported version. You can modify if needed using the `LLVM_VERSION` env var during configure. 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.

It's easy to install all of the required tools:

### Linux

Install LLVM 20 on Ubuntu/Debian:
Install LLVM 21 on Ubuntu/Debian:

```sh
wget https://apt.llvm.org/llvm.sh
chmod +x llvm.sh
sudo ./llvm.sh 20
sudo ./llvm.sh 21
```

Install LLVM 20 on Fedora Linux 40 or newer:
Install LLVM 21 on Fedora Linux 40 or newer:

```sh
sudo dnf install 'clang(major) = 20' 'llvm(major) = 20'
sudo dnf install 'clang(major) = 21' 'llvm(major) = 21'
```

### macOS

Install LLVM 20 with [Homebrew](https://brew.sh):
Install LLVM 21 with [Homebrew](https://brew.sh):

```sh
brew install llvm@20
brew install llvm@21
```

Homebrew won't add any of the tools to your `$PATH`. That's okay; the build script knows how to find them.
Expand All@@ -43,18 +43,18 @@ Homebrew won't add any of the tools to your `$PATH`. That's okay; the build scri

LLVM is downloaded automatically (along with other external binary dependencies) by `PCbuild\build.bat`.

Otherwise, you can install LLVM 20 [by searching for it on LLVM's GitHub releases page](https://github.com/llvm/llvm-project/releases?q=20), 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".**
Otherwise, you can install LLVM 21 [by searching for it on LLVM's GitHub releases page](https://github.com/llvm/llvm-project/releases?q=21), 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".**

Alternatively, you can use [chocolatey](https://chocolatey.org):

```sh
choco install llvm --version=20.1.8
choco install llvm --version=21.1.0
```

### Dev Containers

If you are working on 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 42 base image includes LLVM 20 out of the box.
need to install LLVM as the Fedora 43 base image includes LLVM 21 out of the box.

## Building

Expand Down
4 changes: 2 additions & 2 deletions Tools/jit/_llvm.py
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Expand Up@@ -11,8 +11,8 @@
import _targets


_LLVM_VERSION = "20"
_EXTERNALS_LLVM_TAG = "llvm-20.1.8.0"
_LLVM_VERSION = "21"
_EXTERNALS_LLVM_TAG = "llvm-21.1.4.0"

_P = typing.ParamSpec("_P")
_R = typing.TypeVar("_R")
Expand Down
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