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Because of LLVM inling checks, it's generally not possible to inline a C helper into Rust code, even with LTO: * LLVM doesn't want to inline functions compiled with `-fno-delete-null-pointer-checks` with code compiled without. The C CGUs all have this enabled and Rust CGUs don't. Inlining is okay since this is one of the hardening features that does not change the ABI, and we shouldn't have null pointer dereferences in these helpers. * LLVM doesn't want to inline functions with different list of builtins. C side has `-fno-builtin-wcslen`; `wcslen` is not a Rust builtin, so they should be compatible, but LLVM does not perform inlining due to attributes mismatch. * clang and Rust doesn't have the exact target string. Clang generates `+cmov,+cx8,+fxsr` but Rust doesn't enable them (in fact, Rust will complain if `-Ctarget-feature=+cmov,+cx8,+fxsr` is used). x86-64 always enable these features, so they are in fact the same target string, but LLVM doesn't understand this and so inlining is inhibited. This can be bypassed with `--ignore-tti-inline-compatible`, but this is a hidden option. To fix this, we can add __always_inline on every helper, which skips these LLVM inlining checks. For this purpose, introduce a new __rust_helper macro that needs to be added to every helper. Most helpers already have __rust_helper specified, but there are a few missing. The only consequence of this is that those specific helpers do not get inlined. Signed-off-by: Gary Guo <gary@garyguo.net> Signed-off-by: Alice Ryhl <aliceryhl@google.com> Reviewed-by: Nathan Chancellor <nathan@kernel.org> Tested-by: Nathan Chancellor <nathan@kernel.org> Tested-by: Andreas Hindborg <a.hindborg@kernel.org> Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org> Link: https://patch.msgid.link/20260203-inline-helpers-v2-2-beb8547a03c9@google.com Signed-off-by: Miguel Ojeda <ojeda@kernel.org> |
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| bindings | ||
| helpers | ||
| kernel | ||
| macros | ||
| pin-init | ||
| proc-macro2 | ||
| quote | ||
| syn | ||
| uapi | ||
| .gitignore | ||
| .kunitconfig | ||
| bindgen_parameters | ||
| build_error.rs | ||
| compiler_builtins.rs | ||
| exports.c | ||
| ffi.rs | ||
| Makefile | ||