74f600b990
Allow to disable thinLTO buffer to support lto-embed-bitcode lld feature Hello This change is to fix issue (https://github.com/rust-lang/rust/issues/84395) in which passing "-lto-embed-bitcode=optimized" to lld when linking rust code via linker-plugin-lto doesn't produce the expected result. Instead of emitting a single unified module into a llvmbc section of the linked elf, it emits multiple submodules. This is caused because rustc emits the BC modules after running llvm `createWriteThinLTOBitcodePass` pass. Which in turn triggers a thinLTO linkage and causes the said issue. This patch allows via compiler flag (-Cemit-thin-lto=<bool>) to select between running `createWriteThinLTOBitcodePass` and `createBitcodeWriterPass`. Note this pattern of selecting between those 2 passes is common inside of LLVM code. The default is to match the old behavior.
This directory currently contains some LLVM support code. This will generally be sent upstream to LLVM in time; for now it lives here. NOTE: the LLVM C++ ABI is subject to between-version breakage and must *never* be exposed to Rust. To allow for easy auditing of that, all Rust-exposed types must be typedef-ed as "LLVMXyz", or "LLVMRustXyz" if they were defined here. Functions that return a failure status and leave the error in the LLVM last error should return an LLVMRustResult rather than an int or anything to avoid confusion. When translating enums, add a single `Other` variant as the first one to allow for new variants to be added. It should abort when used as an input. All other types must not be typedef-ed as such.