[Issue 7157] Optimiser is O(n^2) w.r.t. function length

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=7157

--- Comment #5 from Martin Nowak <code at dawg.eu> ---
Most CPU time is spent in `updaterd` and `accumaecpx` if that helps.

https://github.com/D-Programming-Language/dmd/blob/82b031c22f18334a7edeff437260b6802070a9e3/src/backend/gloop.c#L1263
https://github.com/D-Programming-Language/dmd/blob/e43136308f7eb035d046a99a46ffbdaf880413b7/src/backend/gflow.c#L907

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