musl does not implement the symbols required by std for f128 maths.
Disable the associated cfg for all musl targets and adjust the tests
accordingly.
Signed-off-by: Jens Reidel <adrian@travitia.xyz>
`conv-bits-runtime-const` gates `f16` and `f128` tests behind `x86_64`,
but this isn't always accurate. In particular, x86 `MinGW` has an ABI
bug [1] which means things work when linked to our Rust math libraries
but don't work with host libraries. RUST-143405 slightly adjusts which
targets we provide `f16` and `f128` symbols for and effectively removes
MinGW from that list, meaning host libraries start getting linked,
meaning `f16` and `f128` tests start to fail.
Account for this by changing the gates in one such test to
`cfg(target_has_reliable_{f16,f128})` which is the way we should be
gating all behavior related to the types going forward.
`rustfmt` also seems to have formatted the macros which is fine.
[1]: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115054
Support for `f16` and `f128` is varied across targets, backends, and
backend versions. Eventually we would like to reach a point where all
backends support these approximately equally, but until then we have to
work around some of these nuances of support being observable.
Introduce the `cfg_target_has_reliable_f16_f128` internal feature, which
provides the following new configuration gates:
* `cfg(target_has_reliable_f16)`
* `cfg(target_has_reliable_f16_math)`
* `cfg(target_has_reliable_f128)`
* `cfg(target_has_reliable_f128_math)`
`reliable_f16` and `reliable_f128` indicate that basic arithmetic for
the type works correctly. The `_math` versions indicate that anything
relying on `libm` works correctly, since sometimes this hits a separate
class of codegen bugs.
These options match configuration set by the build script at [1]. The
logic for LLVM support is duplicated as-is from the same script. There
are a few possible updates that will come as a follow up.
The config introduced here is not planned to ever become stable, it is
only intended to replace the build scripts for `std` tests and
`compiler-builtins` that don't have any way to configure based on the
codegen backend.
MCP: https://github.com/rust-lang/compiler-team/issues/866
Closes: https://github.com/rust-lang/compiler-team/issues/866
[1]: 555e1d0386/library/std/build.rs (L84-L186)
