soft float ABI used instead of hard float for riscv64gc-unknown-none-elf

[DieracDelta]

A incorrect ABI is used by llvm on the riscv64gc-unknown-none-elf target. The ABI used should be lp64d. I've included a minimum working example of this here.

Expected behavior:

cargo build --target riscv64gc-unknown-none-elf --lib

would produce a library with double float ABI due to the +d extension. What is produced is a library with a single float ABI. The ABI used can be checked by looking at the ELF header:

readelf -h target/riscv64gc-unknown-none-elf/debug/librust_uland.a

This gives back:

...
Flags:                             0x1, RVC, soft-float ABI
...

I'm expecting:

...
Flags:                             0x1, RVC, double-float ABI
...

Note that the riscv64-unknown-linux-gnu target uses the lp64d ABI as expected. Note that it's actually using the wrong ABI (not just setting bits incorrectly in the header). I'm trying to link to a C library that is compiled with the d extension and this fails during linking due to the differing ABIs in use.

[JohnTitor]

Fixed by #83231.