[Issue 22372] Loop index incorrectly optimised out for -release -O

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=22372

--- Comment #7 from Basile-z <b2.temp at gmx.com> ---
by digging further it looks like the problem resides in dmd.backend.gloop
reference counting system. OPInd would be ignored, so when a loop body only
contains an IndexExp and that the IndexExp subscript is the IV (increment value
?), DMD thinks that the IV is not used.

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