Add tgamma and tgammaf

[ankane]

For rust-lang/rust#99747

[ankane]

Not sure I fully understand the failure, but guessing it may be due to tgamma and tgammaf not having this line in libm:

#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]

[Amanieu]

I believe the issue that is this line in tgamma.rs:

n = (n + 1) / 2;

In debug builds this introduces a call to panic because we still emit a check against division by zero. This can be fixed by using the div! macro defined in libm/src/math/mod.rs.

[ankane]

Thanks @Amanieu! I updated the call in this branch. It looks like there may be another panic.

env RUSTFLAGS='-Ccodegen-units=1' cargo test --all --release --features 'unstable musl-reference-tests'

(on Ubuntu 20.04) gives:

libm.458c1a1f-cgu.0:(.text._ZN4core3ptr58drop_in_place$LT$libm..math..tgamma..tgamma..__NoPanic$GT$17ha3e84c801b2d4a51E+0x3): undefined reference to `

ERROR[no-panic]: detected panic in function `tgamma`
'
/usr/bin/ld: /home/vagrant/libm/target/release/deps/libm-dddd41468bd528f3.libm.458c1a1f-cgu.0.rcgu.o: in function `core::ptr::drop_in_place<libm::math::tgammaf::tgammaf::__NoPanic>':
libm.458c1a1f-cgu.0:(.text._ZN4core3ptr60drop_in_place$LT$libm..math..tgammaf..tgammaf..__NoPanic$GT$17h69ee5eb5a9c950f0E+0x3): undefined reference to `

ERROR[no-panic]: detected panic in function `tgammaf`
'
collect2: error: ld returned 1 exit status

Will try to track it down, but please let me know if you have any ideas.

Edit: Looks like it may be in the s function

[ankane]

Looks like it was indexing. Replaced with i! macro, and will submit a PR to libm. Thanks again for the help!

[Amanieu]

I've merged the libm PR, you can update the submodule in this PR.

[ankane]

Great, thanks! Looks like it fixed the test suite.

[Amanieu]

I published a new version of the crate, you can now make PR to rust-lang/rust to update it there.

[ankane]

Perfect, I appreciate all the help (first time contributing to Rust).