[flang-commits] [clang] [flang] [flang] Enable FP sum reassociation by default at O1 and above (PR #218746)

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https://github.com/jeanPerier commented:

Thanks for all the work enabling this @tblah.

I would favor doing this all the time unless explicitly asked by a flag not to do it so that debugging experience is close as possible from the O1/O2 experience (i.e., it makes sense to turn off mem2reg, licm at O0.... when you want the best debugging experience, but here this change does not impact the ability to set breakpoint and inspect variables).

This is consistent with what classic flang is doing (although I am not even sure there is a flag to opt-out) and I see it as an implementation choice rather than an optimization.

I also prefer the initial lowering to FIR to be as much as possible not impacted by the Oxxx flags.

https://github.com/llvm/llvm-project/pull/218746