From: Gary Guo <[email protected]> This config detects if Rust and Clang have matching LLVM major version. All IR or bitcode operations (e.g. LTO) rely on LLVM major version to be matching, otherwise it may generate errors, or worse, miscompile silently due to change of IR semantics.
It's usually suggested to use the exact same LLVM version, but this can be difficult to guarantee. Rust's suggestion [1] is also major-version only, so I think this check is sufficient for the kernel. Link: https://doc.rust-lang.org/rustc/linker-plugin-lto.html [1] Reviewed-by: Andreas Hindborg <[email protected]> Signed-off-by: Gary Guo <[email protected]> Signed-off-by: Matthew Maurer <[email protected]> Signed-off-by: Alice Ryhl <[email protected]> --- init/Kconfig | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/init/Kconfig b/init/Kconfig index cab3ad28ca49e7ac930207c9cde8d431d55dc7af..d35d0ddee573d09997087a0f99dee7c7c9a66ae3 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -82,6 +82,21 @@ config RUSTC_LLVM_VERSION int default $(rustc-llvm-version) +config RUSTC_LLVM_MAJOR_VERSION + int + default $(shell,expr $(rustc-llvm-version) / 10000) + +config RUSTC_CLANG_LLVM_COMPATIBLE + bool + default y if CC_IS_CLANG && RUSTC_LLVM_MAJOR_VERSION = $(shell,expr $(cc-version) / 10000) + help + This indicates whether Rust and Clang use LLVM of the same major + version. + + Operations involving handling LLVM IR or bitcode (e.g. cross-language + LTO) requires the same LLVM major version to work properly. For best + compatibility it is recommended that the exact same LLVM is used. + config CC_CAN_LINK bool default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag)) if 64BIT -- 2.52.0.158.g65b55ccf14-goog
