linux/rust
Miguel Ojeda 02dfd63afe rust: add intrinsics to fix -Os builds
Alice reported [1] that an arm64 build failed with:

    ld.lld: error: undefined symbol: __extendsfdf2
    >>> referenced by core.a6f5fc5794e7b7b3-cgu.0
    >>>               rust/core.o:(<f32>::midpoint) in archive vmlinux.a
    >>> referenced by core.a6f5fc5794e7b7b3-cgu.0
    >>>               rust/core.o:(<f32>::midpoint) in archive vmlinux.a

    ld.lld: error: undefined symbol: __truncdfsf2
    >>> referenced by core.a6f5fc5794e7b7b3-cgu.0
    >>>               rust/core.o:(<f32>::midpoint) in archive vmlinux.a

Rust 1.80.0 or later together with `CONFIG_CC_OPTIMIZE_FOR_SIZE=y`
is what triggers it.

In addition, x86_64 builds also fail the same way.

Similarly, compiling with Rust 1.82.0 (currently in nightly) makes
another one appear, possibly due to the LLVM 19 upgrade there:

    ld.lld: error: undefined symbol: __eqdf2
    >>> referenced by core.20495ea57a9f069d-cgu.0
    >>>               rust/core.o:(<f64>::next_up) in archive vmlinux.a
    >>> referenced by core.20495ea57a9f069d-cgu.0
    >>>               rust/core.o:(<f64>::next_down) in archive vmlinux.a

Gary adds [1]:

> Usually the fix on rustc side is to mark those functions as `#[inline]`
>
> All of {midpoint,next_up,next_down} are indeed unstable functions not
> marked as inline...

Fix all those by adding those intrinsics to our usual workaround.

[ Trevor quickly submitted a fix to upstream Rust [2] that has already
  been merged, to be released in Rust 1.82.0 (2024-10-17). - Miguel ]

Cc: Gary Guo <gary@garyguo.net>
Reported-by: Alice Ryhl <aliceryhl@google.com>
Closes: https://rust-for-linux.zulipchat.com/#narrow/stream/x/topic/x/near/455637364 [1]
Reviewed-by: Trevor Gross <tmgross@umich.edu>
Tested-by: Alice Ryhl <aliceryhl@google.com>
Tested-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Link: https://github.com/rust-lang/rust/pull/128749 [2]
Link: https://lore.kernel.org/r/20240806150619.192882-1-ojeda@kernel.org
[ Shortened Zulip link. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
2024-08-10 00:05:10 +02:00
..
bindings Rust changes for v6.11 2024-07-27 13:44:54 -07:00
kernel Rust changes for v6.11 2024-07-27 13:44:54 -07:00
macros rust: macros: indent list item in module!'s docs 2024-07-29 14:23:54 +02:00
uapi rust: allow dead_code for never constructed bindings 2024-07-10 10:28:51 +02:00
.gitignore rust: support running Rust documentation tests as KUnit ones 2023-07-19 09:32:53 -06:00
bindgen_parameters rust: Ignore preserve-most functions 2023-12-13 01:09:55 +01:00
build_error.rs rust: add build_error crate 2022-12-04 01:59:16 +01:00
compiler_builtins.rs rust: add intrinsics to fix -Os builds 2024-08-10 00:05:10 +02:00
exports.c rust: replace <linux/module.h> with <linux/export.h> in rust/exports.c 2023-12-13 01:09:55 +01:00
helpers.c Rust changes for v6.11 2024-07-27 13:44:54 -07:00
Makefile rust: add intrinsics to fix -Os builds 2024-08-10 00:05:10 +02:00