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Typical uses of ThinLTO don't have any use for this as a standalone file, but distributed ThinLTO uses this to make the linker phase more efficient. With clang you'd do something like `clang -flto=thin -fthin-link-bitcode=foo.indexing.o -c foo.c` and then get both foo.o (full of bitcode) and foo.indexing.o (just the summary or index part of the bitcode). That's then usable by a two-stage linking process that's more friendly to distributed build systems like bazel, which is why I'm working on this area. I talked some to @teresajohnson about naming in this area, as things seem to be a little confused between various blog posts and build systems. "bitcode index" and "bitcode summary" tend to be a little too ambiguous, and she tends to use "thin link bitcode" and "minimized bitcode" (which matches the descriptions in LLVM). Since the clang option is thin-link-bitcode, I went with that to try and not add a new spelling in the world. Per @dtolnay, you can work around the lack of this by using `lld --thinlto-index-only` to do the indexing on regular .o files of bitcode, but that is a bit wasteful on actions when we already have all the information in rustc and could just write out the matching minimized bitcode. I didn't test that at all in our infrastructure, because by the time I learned that I already had this patch largely written. |
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| .. | ||
| .editorconfig | ||
| ArchiveWrapper.cpp | ||
| CoverageMappingWrapper.cpp | ||
| Linker.cpp | ||
| LLVMWrapper.h | ||
| PassWrapper.cpp | ||
| README | ||
| RustWrapper.cpp | ||
| SuppressLLVMWarnings.h | ||
| SymbolWrapper.cpp | ||
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.