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Enable full LTO on Python 3.12 and 3.13 #529

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Enable full LTO on Python 3.12 and 3.13 #529

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6 changes: 5 additions & 1 deletion cpython-unix/build-cpython.sh
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Expand Up @@ -427,7 +427,11 @@ if [ -n "${CPYTHON_OPTIMIZED}" ]; then
fi

if [ -n "${CPYTHON_LTO}" ]; then
CONFIGURE_FLAGS="${CONFIGURE_FLAGS} --with-lto"
# On Python 3.12 and 3.13, `--with-lto` enables ThinLTO by default, while on other versions it
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What about 3.14? Did it change in 3.14?

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3.14a5 and below still defaults to ThinLTO. 3.14a6 (upcoming) will default back to fullLTO.

It's safe to just pass --with-lto=full to all versions of 3.14. That will always work.

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Yes the linked documentation says they're reverting the ThinLTO default in 3.14.

Seems best to just set it on all versions.

# enables full LTO. We prefer runtime performance over build time, so force full on all
# versions.
# See https://docs.python.org/3.14/using/configure.html#cmdoption-with-lto
CONFIGURE_FLAGS="${CONFIGURE_FLAGS} --with-lto=full"
fi

# Python 3.11 introduces a --with-build-python to denote the host Python.
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