[Issue 17562] Tangent function returns NaN for abs(input) >= 2^63

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=17562

--- Comment #1 from github-bugzilla at puremagic.com ---
Commit pushed to master at https://github.com/dlang/phobos

https://github.com/dlang/phobos/commit/0fb66f092b897b55318509c6582008b3f912311a
Fix issue 17562 - tan returning -nan for inputs where abs(x) >= 2^63

The fptan instruction pushes a 1.0 onto the FPU register stack after a
successful operation, but when abs(input) >= 2^63 the C2 flag is set to
indicate that the input was out of bounds, and it doesn't push the 1.0.

Prior to this PR, the top value of the FPU stack was popped irrespective
of whether C2 was set, which in the case of an out-of-bounds input
caused the input to be removed from the stack and ultimately resulted in
an incorrect return value of -nan. This PR changes this behavior, only
popping after fptan when C2 was not set.

See: http://x86.renejeschke.de/html/file_module_x86_id_109.html

* Added unit tests for handling out-of-range inputs of fptan

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