Use full LTO for all builds #343
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Fidget-Spinner
commented
Jan 12, 2025
| @@ -320,7 +320,7 @@ jobs: | |||
| if: ${{ steps.should_run.outputs.should_run != 'false' }} | |||
| run: | | |||
| cd cpython | |||
| ./configure ${{ inputs.pgo == true && '--enable-optimizations --with-lto=yes' || '' }} ${{ inputs.tier2 == true && '--enable-experimental-jit=interpreter' || '' }} ${{ inputs.jit == true && '--enable-experimental-jit=yes' || '' }} ${{ inputs.nogil == true && '--disable-gil' || '' }} | |||
| ./configure ${{ inputs.pgo == true && '--enable-optimizations --with-lto=full' || '' }} ${{ inputs.tier2 == true && '--enable-experimental-jit=interpreter' || '' }} ${{ inputs.jit == true && '--enable-experimental-jit=yes' || '' }} ${{ inputs.nogil == true && '--disable-gil' || '' }} | |||
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This is a bit tricky. Apple Clang defaults to ThinLTO on recent versions as well. So after this commit, we would need to be careful when benchmarking and make sure it's comparing to a recent CPython commit (and not an old one prior to this commit).
I'm still in favour of this change anyways, because full LTO produces more reproducible benchmarking results, based on our experience in python/cpython#122580
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We can merge this and then re-run all of the baselines (3.10, 3.11, 3.13) on macOS, and then backfill all of the comparisons. |
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Closes #342
GCC defaults to full LTO with
--with-lto=yespassed. Clang defaults to ThinLTO with--with-lto=yespassed. You need--with-lto=fullto enable full LTO.