Commit 02dfd63a authored by Miguel Ojeda's avatar Miguel Ojeda
Browse files

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: default avatarAlice Ryhl <aliceryhl@google.com>
Closes: https://rust-for-linux.zulipchat.com/#narrow/stream/x/topic/x/near/455637364

 [1]
Reviewed-by: default avatarTrevor Gross <tmgross@umich.edu>
Tested-by: default avatarAlice Ryhl <aliceryhl@google.com>
Tested-by: default avatarBoqun Feng <boqun.feng@gmail.com>
Reviewed-by: default avatarGary 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: default avatarMiguel Ojeda <ojeda@kernel.org>
parent 869b5016

rust/Makefile

+2 −2
Original line number Diff line number Diff line
@@ -354,8 +354,8 @@ rust-analyzer: 
		$(if $(KBUILD_EXTMOD),$(extmod_prefix),$(objtree))/rust-project.json



redirect-intrinsics = \

	__addsf3 __eqsf2 __gesf2 __lesf2 __ltsf2 __mulsf3 __nesf2 __unordsf2 \

	__adddf3 __ledf2 __ltdf2 __muldf3 __unorddf2 \

	__addsf3 __eqsf2 __extendsfdf2 __gesf2 __lesf2 __ltsf2 __mulsf3 __nesf2 __truncdfsf2 __unordsf2 \

	__adddf3 __eqdf2 __ledf2 __ltdf2 __muldf3 __unorddf2 \

	__muloti4 __multi3 \

	__udivmodti4 __udivti3 __umodti3

rust/compiler_builtins.rs

+3 −0
Original line number Diff line number Diff line
@@ -40,16 +40,19 @@ pub extern "C" fn $ident() { 
define_panicking_intrinsics!("`f32` should not be used", {

    __addsf3,

    __eqsf2,

    __extendsfdf2,

    __gesf2,

    __lesf2,

    __ltsf2,

    __mulsf3,

    __nesf2,

    __truncdfsf2,

    __unordsf2,

});



define_panicking_intrinsics!("`f64` should not be used", {

    __adddf3,

    __eqdf2,

    __ledf2,

    __ltdf2,

    __muldf3,