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coverage: Correctly report and check LLVM's coverage mapping version

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This commit is contained in:
Zalathar 2024-02-13 23:00:49 +11:00
parent a77322c16f
commit 8289dadfbc
2 changed files with 24 additions and 10 deletions
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29
compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs
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@ -17,11 +17,11 @@ use rustc_span::Symbol;
/// Generates and exports the Coverage Map.
///
/// Rust Coverage Map generation supports LLVM Coverage Mapping Format version
/// 6 (zero-based encoded as 5), as defined at
/// [LLVM Code Coverage Mapping Format](https://github.com/rust-lang/llvm-project/blob/rustc/13.0-2021-09-30/llvm/docs/CoverageMappingFormat.rst#llvm-code-coverage-mapping-format).
/// Rust Coverage Map generation supports LLVM Coverage Mapping Format versions
/// 6 and 7 (encoded as 5 and 6 respectively), as described at
/// [LLVM Code Coverage Mapping Format](https://github.com/rust-lang/llvm-project/blob/rustc/18.0-2024-02-13/llvm/docs/CoverageMappingFormat.rst).
/// These versions are supported by the LLVM coverage tools (`llvm-profdata` and `llvm-cov`)
/// bundled with Rust's fork of LLVM.
/// distributed in the `llvm-tools-preview` rustup component.
///
/// Consequently, Rust's bundled version of Clang also generates Coverage Maps compliant with
/// the same version. Clang's implementation of Coverage Map generation was referenced when
@ -31,10 +31,21 @@ use rustc_span::Symbol;
pub fn finalize(cx: &CodegenCx<'_, '_>) {
let tcx = cx.tcx;
// Ensure the installed version of LLVM supports Coverage Map Version 6
// (encoded as a zero-based value: 5), which was introduced with LLVM 13.
let version = coverageinfo::mapping_version();
assert_eq!(version, 5, "The `CoverageMappingVersion` exposed by `llvm-wrapper` is out of sync");
// Ensure that LLVM is using a version of the coverage mapping format that
// agrees with our Rust-side code. Expected versions (encoded as n-1) are:
// - `CovMapVersion::Version6` (5) used by LLVM 13-17
// - `CovMapVersion::Version7` (6) used by LLVM 18
let covmap_version = {
let llvm_covmap_version = coverageinfo::mapping_version();
let expected_versions = 5..=6;
assert!(
expected_versions.contains(&llvm_covmap_version),
"Coverage mapping version exposed by `llvm-wrapper` is out of sync; \
expected {expected_versions:?} but was {llvm_covmap_version}"
);
// This is the version number that we will embed in the covmap section:
llvm_covmap_version
};
debug!("Generating coverage map for CodegenUnit: `{}`", cx.codegen_unit.name());
@ -74,7 +85,7 @@ pub fn finalize(cx: &CodegenCx<'_, '_>) {
// Generate the coverage map header, which contains the filenames used by
// this CGU's coverage mappings, and store it in a well-known global.
let cov_data_val = generate_coverage_map(cx, version, filenames_size, filenames_val);
let cov_data_val = generate_coverage_map(cx, covmap_version, filenames_size, filenames_val);
coverageinfo::save_cov_data_to_mod(cx, cov_data_val);
let mut unused_function_names = Vec::new();

5
compiler/rustc_llvm/llvm-wrapper/CoverageMappingWrapper.cpp
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@ -205,5 +205,8 @@ extern "C" void LLVMRustCoverageWriteMappingVarNameToString(RustStringRef Str) {
}
extern "C" uint32_t LLVMRustCoverageMappingVersion() {
return coverage::CovMapVersion::Version6;
// This should always be `CurrentVersion`, because that's the version LLVM
// will use when encoding the data we give it. If for some reason we ever
// want to override the version number we _emit_, do it on the Rust side.
return coverage::CovMapVersion::CurrentVersion;
}