[Issue 18730] dmd miscompiles core.bitop.bt with -O

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=18730

--- Comment #5 from ag0aep6g <ag0aep6g at gmail.com> ---
(In reply to ag0aep6g from comment #3)
> 2) File a new issue for the larger problem: core.bitop.bt's bitnum parameter
> is a size_t when it should be a ptrdiff_t. Then bt's body has to be adjusted
> for that, because D doesn't have negatives indices. And dmd has to be
> adjusted to recognize the new body.

Filed that as issue 18734.

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