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Most coverage metadata is encoded into two sections in the final executable. The `__llvm_covmap` section mostly just contains a list of filenames, while the `__llvm_covfun` section contains encoded coverage maps for each instrumented function. The catch is that each per-function record also needs to contain a hash of the filenames list that it refers to. Historically this was handled by assembling most of the per-function data into a temporary list, then assembling the filenames buffer, then using the filenames hash to emit the per-function data, and then finally emitting the filenames table itself. However, now that we build the filenames table up-front (via a separate traversal of the per-function data), we can hash and emit that part first, and then emit each of the per-function records immediately after building. This removes the awkwardness of having to temporarily store nearly-complete per-function records. |
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| 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.