Missing __truncdfsf2 for aarch64-unknown-none-softfloat

[rahealy]

I took a look at the C files referenced in this repo's README.md but don't feel that I'm qualified to make the port to rust.

I'd be very grateful if this function could be prioritized for implementation. Thank you.

[vinc]

I have the same issue it seems on a project targeting 86_64-unknown-none and -mmx,-sse,+soft-float when using libm::atan2:

  = note: rust-lld: error: undefined symbol: __truncdfsf2
          >>> referenced by atan.rs:88 (/home/v/.cargo/registry/src/github.com-1ecc6299db9ec823/libm-0.2.1/src/math/atan.rs:88)
          >>>               libm-2ef216d6f8fb20a3.libm.6bk0rn0r-cgu.14.rcgu.o:(libm::math::atan::atan::h55c5acf004540e1c) in archive /home/v/src/vinc/moros/target/x86_64-moros/debug/deps/liblibm-2ef216d6f8fb20a3.rlib

[andre-richter]

There are two bare-metal aarch64 targets for rustc:

aarch64-unknown-none
aarch64-unknown-none-softfloat

The latter is intended for Kernels or Hypervisors where floating point code would be concenptionally ill-suited in most cases.

It just happens that the current rust compiler infrastructure does fall back to fixed point implementations of float operations if avail, hence the unusual target name.

Hitting a case where a float intrinsic is missing with the softfloat target is probably either a good hint that you accidentally included float code where you should not, or that the aarch64-unknown-none target is what you want instead (which would run your float code heaps faster because it utilizes the hardware floating point units of the processor).

[dbeckwith]

Ran into the same linker error on x86_64-unknown-none with the soft-float feature enabled. rust-num/num-traits#167 has the details. I'll look into the implementation that was going to be added in #262 and see if that works for me.

[HTGAzureX1212]

Just ran into this issue today whilst trying to target x86_64-unknown-uefi, when using embedded-graphics.

[sajattack]

Same thing on mips2 with +single-float (mipsel-sony-psp tier 3 target).