mcdc-coverage: Add FFI for getting Bitmap IPSK, Bump CoverageMappingVersion

Author: RenjiSann

compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs

@@ -31,10 +31,10 @@ 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.
+    // Ensure the installed version of LLVM supports Coverage Map Version 7
+    // (encoded as a zero-based value: 6), 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");
+    assert_eq!(version, 6, "The `CoverageMappingVersion` exposed by `llvm-wrapper` is out of sync");
 
     debug!("Generating coverage map for CodegenUnit: `{}`", cx.codegen_unit.name());
 
@@ -276,6 +276,7 @@ fn encode_mappings_for_function(
 /// Construct coverage map header and the array of function records, and combine them into the
 /// coverage map. Save the coverage map data into the LLVM IR as a static global using a
 /// specific, well-known section and name.
+/// https://llvm.org/docs/CoverageMappingFormat.html#llvm-ir-representation
 fn generate_coverage_map<'ll>(
     cx: &CodegenCx<'ll, '_>,
     version: u32,

compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs

@@ -278,3 +278,13 @@ pub(crate) fn covfun_section_name(cx: &CodegenCx<'_, '_>) -> String {
     })
     .expect("Rust Coverage function record section name failed UTF-8 conversion")
 }
+
+/// Returns the section name for the MC/DC Bitmap section passed to the linker.
+/// FIXME: Remove allow deadcode
+#[allow(dead_code)]
+pub(crate) fn prf_bits_section_name(cx: &CodegenCx<'_, '_>) -> String {
+    llvm::build_string(|s| unsafe {
+        llvm::LLVMRustCoverageWriteBitmapSectionNameToString(cx.llmod, s);
+    })
+    .expect("Rust Coverage function record section name failed UTF-8 conversion")
+}

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -1788,6 +1788,9 @@ extern "C" {
     #[allow(improper_ctypes)]
     pub fn LLVMRustCoverageWriteFuncSectionNameToString(M: &Module, Str: &RustString);
 
+    #[allow(improper_ctypes)]
+    pub fn LLVMRustCoverageWriteBitmapSectionNameToString(M: &Module, Str: &RustString);
+
     #[allow(improper_ctypes)]
     pub fn LLVMRustCoverageWriteMappingVarNameToString(Str: &RustString);
 

compiler/rustc_llvm/llvm-wrapper/CoverageMappingWrapper.cpp

@@ -204,12 +204,17 @@ extern "C" void LLVMRustCoverageWriteFuncSectionNameToString(LLVMModuleRef M,
   WriteSectionNameToString(M, IPSK_covfun, Str);
 }
 
+extern "C" void LLVMRustCoverageWriteBitmapSectionNameToString(LLVMModuleRef M,
+                                                             RustStringRef Str) {
+  WriteSectionNameToString(M, IPSK_bitmap, Str);
+}
+
 extern "C" void LLVMRustCoverageWriteMappingVarNameToString(RustStringRef Str) {
   auto name = getCoverageMappingVarName();
   auto OS = RawRustStringOstream(Str);
   OS << name;
 }
 
 extern "C" uint32_t LLVMRustCoverageMappingVersion() {
-  return coverage::CovMapVersion::Version6;
+  return coverage::CovMapVersion::Version7;
 }