[flang-commits] [flang] [llvm] [flang-rt] Copy out only the modified suffix of an argument temporary (PR #222101)

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https://github.com/jeanPerier approved this pull request.

Thanks for following up on this @eugeneepshteyn.

Can you run perf numbers on CPU2017/521.wrf if you have not already? While I am not 100% sure, I think this is a benchmark that emits copy-out (although I am not sure if they are used at runtime given the data is contiguous).

Overall this seems good to me given statistically: assumed shape arrays passed to explicit shape are likely often contiguous (no impact with your change), and likely more often read than modified by subroutines (a win with your change).

And the simplification this will allow around passing compile time array constant (avoid unnecessary runtime copies and allowing LLVM to rely on the read-only aspect after inlining) looks like big wins to me.

https://github.com/llvm/llvm-project/pull/222101