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disable ccache by default when building llvm libraries #4885

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disable ccache by default when building llvm libraries #4885

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bf9612c
feat: add --use-ccache CLI argument to build_llvm.py
lum1n0us Mar 20, 2026
89f34f1
feat: disable ccache by default, enable with --use-ccache flag
lum1n0us Mar 20, 2026
299e926
docs: add note about --use-ccache flag in product-mini README
lum1n0us Mar 20, 2026
064adff
docs: update LLVM_CCACHE_BUILD example in benchmarks README
lum1n0us Mar 20, 2026
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13 changes: 9 additions & 4 deletions build-scripts/build_llvm.py
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Original file line number Diff line number Diff line change
Expand Up @@ -48,7 +48,7 @@ def query_llvm_version(llvm_info):
return response['sha']


def build_llvm(llvm_dir, platform, backends, projects, use_clang=False, extra_flags=''):
def build_llvm(llvm_dir, platform, backends, projects, use_clang=False, extra_flags='', use_ccache=False):
LLVM_COMPILE_OPTIONS = [
'-DCMAKE_BUILD_TYPE:STRING="Release"',
"-DCMAKE_EXPORT_COMPILE_COMMANDS=ON",
Expand All @@ -68,8 +68,8 @@ def build_llvm(llvm_dir, platform, backends, projects, use_clang=False, extra_fl
"-DLLVM_OPTIMIZED_TABLEGEN:BOOL=ON",
]

# ccache is not available on Windows
if not "windows" == platform:
# ccache is opt-in via --use-ccache flag
if not "windows" == platform and use_ccache:
LLVM_COMPILE_OPTIONS.append("-DLLVM_CCACHE_BUILD:BOOL=ON")
# perf support is available on Linux only
if "linux" == platform:
Expand Down Expand Up @@ -270,6 +270,11 @@ def main():
action="store_true",
help="use clang instead of gcc",
)
parser.add_argument(
"--use-ccache",
action="store_true",
help="enable ccache for faster incremental LLVM builds (disabled by default to reduce CI storage consumption, recommended for local development)",
)
parser.add_argument(
"--extra-cmake-flags",
type=str,
Expand Down Expand Up @@ -334,7 +339,7 @@ def main():
if (
build_llvm(
llvm_dir, platform, options.arch, options.project, options.use_clang,
options.extra_cmake_flags
options.extra_cmake_flags, options.use_ccache
)
is not None
):
Expand Down
6 changes: 6 additions & 0 deletions product-mini/README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -79,6 +79,12 @@ cd product-mini/platforms/linux/
./build_llvm.sh (The llvm source code is cloned under <wamr_root_dir>/core/deps/llvm and auto built)
```

Note: By default, ccache is disabled to reduce CI storage consumption. For local development with frequent LLVM rebuilds, you can enable ccache for faster incremental builds by using the `--use-ccache` flag:
``` Bash
cd <wamr_root_dir>/build-scripts
python3 build_llvm.py --arch X86 --use-ccache
```

Then pass argument `-DWAMR_BUILD_JIT=1` to cmake to enable LLVM JIT:
``` Bash
mkdir build && cd build
Expand Down
2 changes: 2 additions & 0 deletions tests/benchmarks/README.md
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Expand Up @@ -65,3 +65,5 @@ cmake ../llvm \
ninja -j 8
# tool `llvm-profdata` is generated under this folder.
```

> **Note**: The example above shows `-DLLVM_CCACHE_BUILD:BOOL=ON` for enabling ccache in the cmake configuration. When using the `build_llvm.py` script, ccache is disabled by default to reduce CI storage consumption. To enable it with the script, use: `python3 build_llvm.py --use-ccache --arch X86`
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