[llvm] [LoopInterchange] Enable it by default (PR #124911)

Ryotaro Kasuga via llvm-commits llvm-commits at lists.llvm.org
Tue Jul 1 06:33:18 PDT 2025


kasuga-fj wrote:

I tried some of the improvements I suggested earlier. Here are the results:

https://llvm-compile-time-tracker.com/compare.php?from=7e830f76711f0dfc66780ea13cf780b8760b458b&to=c365bfe1f1c0e7fddb8245cb9ab3999ae30e44b5&stat=instructions%3Au

At least the spike (e.g., over 20% in `CMakeFiles/lencod.dir/q_matrix.c.o`) has been mitigated. I'm not sure if this result is "acceptable", and this might also fall under the kind of my own "completely arbitrary" opinion, but I think these improvements should land before enabling by default.

> The concession I am willing to make is to enable this only with -O3.

What do you think about disabling in ThinLTO? Based on the results above, the compile-time impact appears to be more significant within ThinLTO.

https://github.com/llvm/llvm-project/pull/124911


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