74b8d324eb
Both GCC and Clang write by default a `.comment` section with compiler information: ```txt $ gcc -c -xc /dev/null && readelf -p '.comment' null.o String dump of section '.comment': [ 1] GCC: (GNU) 11.2.0 $ clang -c -xc /dev/null && readelf -p '.comment' null.o String dump of section '.comment': [ 1] clang version 14.0.1 (https://github.com/llvm/llvm-project.git c62053979489ccb002efe411c3af059addcb5d7d) ``` They also implement the `-Qn` flag to avoid doing so: ```txt $ gcc -Qn -c -xc /dev/null && readelf -p '.comment' null.o readelf: Warning: Section '.comment' was not dumped because it does not exist! $ clang -Qn -c -xc /dev/null && readelf -p '.comment' null.o readelf: Warning: Section '.comment' was not dumped because it does not exist! ``` So far, `rustc` only does it for WebAssembly targets and only when debug info is enabled: ```txt $ echo 'fn main(){}' | rustc --target=wasm32-unknown-unknown --emit=llvm-ir -Cdebuginfo=2 - && grep llvm.ident rust_out.ll !llvm.ident = !{!27} ``` In the RFC part of this PR it was decided to always add the information, which gets us closer to other popular compilers. An opt-out flag like GCC and Clang may be added later on if deemed necessary. Implementation-wise, this covers both `ModuleLlvm::new()` and `ModuleLlvm::new_metadata()` cases by moving the addition to `context::create_module` and adds a few test cases. ThinLTO also sees the `llvm.ident` named metadata duplicated (in temporary outputs), so this deduplicates it like it is done for `wasm.custom_sections`. The tests also check this duplication does not take place. Signed-off-by: Miguel Ojeda <ojeda@kernel.org> |
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| .. | ||
| src | ||
| Cargo.toml | ||
| messages.ftl | ||
| README.md | ||
The codegen crate contains the code to convert from MIR into LLVM IR,
and then from LLVM IR into machine code. In general it contains code
that runs towards the end of the compilation process.
For more information about how codegen works, see the rustc dev guide.