Reland: Use -fdebug-compilation-dir to form absolute paths in coverage mappings

[keith]

Summary

This reverts commit 62808631acceaa8b78f8ab9b407eb6b943ff5f77.

This was previously reverted because llvm-cov's -path-equivalence usage
wasn't working as expected. This does work with
-path-equivalence=.,/bar when used with -fdebug-compilation-dir .

More discussion: https://lists.llvm.org/pipermail/cfe-dev/2020-June/065668.html

[keith]

Update relative paths to include the leading ./

This makes these remappings more analogous to lldb's source remapping, and
makes using -path-equivalence with llvm-cov more familiar.

[vsk]

Lgtm. Thanks for making the addition to the command guide!

[keith]

FYI I actually removed that piece this morning since I felt like since this now supports -path-equivalence=.,foo which is the "expected" behavior from lldb, that was "good enough". lmk if you want me to add it back!

[vsk]

In D81122#2074213, @keith wrote:

FYI I actually removed that piece this morning since I felt like since this now supports -path-equivalence=.,foo which is the "expected" behavior from lldb, that was "good enough". lmk if you want me to add it back!

I missed the fact that there's already some discussion of working with remote builds in the command guide. I don't think it needs to be changed.

Separately, @phosek pointed out that there might be an issue with changing the way paths work in coverage mappings based on -fdebug-prefix-map or -fdebug-compilation-dir alone. Mind holding off on landing this until we pick some way to resolve the issue?

[keith]

https://reviews.llvm.org/D83154

clang/lib/CodeGen/CoverageMappingGen.h

struct FunctionInfo {
     bool IsUsed;
   };
 
   CodeGenModule &CGM;
   CoverageSourceInfo &SourceInfo;
   llvm::SmallDenseMap<const FileEntry *, unsigned, 8> FileEntries;
   std::vector<llvm::Constant *> FunctionNames;
   std::vector<FunctionInfo> FunctionRecords;
+  SmallString<256> CWD;
+
+  std::string normalizeFilename(StringRef Filename);
 
   /// Emit a function record.
   void emitFunctionMappingRecord(const FunctionInfo &Info,
                                  uint64_t FilenamesRef);
 
 public:
-  CoverageMappingModuleGen(CodeGenModule &CGM, CoverageSourceInfo &SourceInfo)
-      : CGM(CGM), SourceInfo(SourceInfo) {}
+  CoverageMappingModuleGen(CodeGenModule &CGM, CoverageSourceInfo &SourceInfo);
 
   CoverageSourceInfo &getSourceInfo() const {
     return SourceInfo;
   }
 
   /// Add a function's coverage mapping record to the collection of the
   /// function mapping records.
   void addFunctionMappingRecord(llvm::GlobalVariable *FunctionName,

clang/lib/CodeGen/CoverageMappingGen.cpp

struct CounterCoverageMappingBuilder
   }
 
   void VisitLambdaExpr(const LambdaExpr *LE) {
     // Lambdas are treated as their own functions for now, so we shouldn't
     // propagate counts into them.
   }
 };
 
-std::string normalizeFilename(StringRef Filename) {
-  llvm::SmallString<256> Path(Filename);
-  llvm::sys::fs::make_absolute(Path);
-  llvm::sys::path::remove_dots(Path, /*remove_dot_dot=*/true);
-  return std::string(Path);
-}
-
 } // end anonymous namespace
 
 static void dump(llvm::raw_ostream &OS, StringRef FunctionName,
                  ArrayRef<CounterExpression> Expressions,
                  ArrayRef<CounterMappingRegion> Regions) {
   OS << FunctionName << ":\n";
   CounterMappingContext Ctx(Expressions);
   for (const auto &R : Regions) {
OS << "File " << R.FileID << ", " << R.LineStart << ":" << R.ColumnStart
        << " -> " << R.LineEnd << ":" << R.ColumnEnd << " = ";
     Ctx.dump(R.Count, OS);
     if (R.Kind == CounterMappingRegion::ExpansionRegion)
       OS << " (Expanded file = " << R.ExpandedFileID << ")";
     OS << "\n";
   }
 }
 
+CoverageMappingModuleGen::CoverageMappingModuleGen(
+    CodeGenModule &CGM, CoverageSourceInfo &SourceInfo)
+    : CGM(CGM), SourceInfo(SourceInfo) {
+  // Honor -fdebug-compilation-dir in paths in coverage data. Otherwise, use the
+  // regular working directory when normalizing paths.
+  if (!CGM.getCodeGenOpts().DebugCompilationDir.empty())
+    CWD = CGM.getCodeGenOpts().DebugCompilationDir;
+  else
+    llvm::sys::fs::current_path(CWD);
+}
+
+std::string CoverageMappingModuleGen::normalizeFilename(StringRef Filename) {
+  llvm::SmallString<256> Path(Filename);
+  llvm::sys::path::remove_dots(Path, /*remove_dot_dot=*/true);
+  llvm::sys::fs::make_absolute(CWD, Path);
+  return Path.str().str();
+}
+
 static std::string getInstrProfSection(const CodeGenModule &CGM,
                                        llvm::InstrProfSectKind SK) {
   return llvm::getInstrProfSectionName(
       SK, CGM.getContext().getTargetInfo().getTriple().getObjectFormat());
 }
 
 void CoverageMappingModuleGen::emitFunctionMappingRecord(
     const FunctionInfo &Info, uint64_t FilenamesRef) {

clang/test/CoverageMapping/debug-dir.cpp

+// %s expands to an absolute path, so to test relative paths we need to create a
+// clean directory, put the source there, and cd into it.
+// RUN: rm -rf %t
+// RUN: mkdir -p %t/foo/bar/baz
+// RUN: cp %s %t/foo/bar/baz/debug-dir.cpp
+// RUN: cd %t/foo/bar
+
+// RUN: %clang_cc1 -fprofile-instrument=clang -fcoverage-mapping -emit-llvm -mllvm -enable-name-compression=false -main-file-name debug-dir.cpp baz/debug-dir.cpp  -o - | FileCheck -check-prefix=ABSOLUTE %s
+//
+// ABSOLUTE: @__llvm_coverage_mapping = {{.*"\\01.*foo.*bar.*baz.*debug-dir\.cpp}}
+
+// RUN: %clang_cc1 -fprofile-instrument=clang -fcoverage-mapping -emit-llvm -mllvm -enable-name-compression=false -main-file-name debug-dir.cpp baz/debug-dir.cpp -fdebug-compilation-dir . -o - | FileCheck -check-prefix=RELATIVE %s
+//
+// RELATIVE: @__llvm_coverage_mapping = {{.*"\\01[^/]*\.(/|\\\\)baz.*debug-dir\.cpp}}
+
+void f1() {}