[Issue 20991] Optimizer is not unlining various forms of simple loops

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=20991

--- Comment #2 from Walter Bright <bugzilla at digitalmars.com> ---
More unrolling information: https://github.com/dlang/phobos/pull/7534

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