[MC/DC][Coverage] Enable profile correlation for MC/DC

When using the `-fcoverage-mcdc` option in profile correlation mode MC/DC
coverage is not actually collected.

In binary profile correlation mode this completes elements of a vector of
per-function profile data structures called `Data` with BitmapPtr and
NumBitmapBytes values that are taken from profile data section in the same way
as it is done for Counters.

In debug info correlation mode this adds new `Profile Bitmap Type` DIEs to
DWARFContext. These entries contain FunctionName and NumBitmapBits for
functions. They are used by `correlateProfileDataImpl()` function to obtain
BitmapPtr and NumBitmapBytes values to complete the corresponding elements of
the vector of per-function profile data structures called `Data`. Creating and
reading these new DIEs occur in the same way as it is done for DIEs of the type
`Profile Data Type`.

Fixes #97385

Author: belyaevrd

compiler-rt/lib/profile/InstrProfilingWriter.c

@@ -320,6 +320,7 @@ COMPILER_RT_VISIBILITY int lprofWriteDataImpl(
   /* The data and names sections are omitted in lightweight mode. */
   if (NumData == 0 && NamesSize == 0) {
     Header.CountersDelta = 0;
+    Header.BitmapDelta = 0;
     Header.NamesDelta = 0;
   }
 

compiler-rt/test/profile/Inputs/instrprof-mcdc-correlation.cpp

@@ -0,0 +1,14 @@
+void test(bool a, bool b, bool c, bool d) {
+  if ((a && b) || (c && d))
+    ;
+  if (b && c)
+    ;
+}
+
+int main() {
+  test(true, true, true, true);
+  test(true, true, false, true);
+  test(true, false, true, true);
+  (void)0;
+  return 0;
+}

compiler-rt/test/profile/instrprof-mcdc-correlation.c

@@ -0,0 +1,21 @@
+// REQUIRES: linux || windows
+// Default
+// RUN: %clang -o %t.normal -fprofile-instr-generate -fcoverage-mapping -fcoverage-mcdc %S/Inputs/instrprof-mcdc-correlation.cpp
+// RUN: env LLVM_PROFILE_FILE=%t.profraw %run %t.normal
+// RUN: llvm-profdata merge -o %t.normal.profdata %t.profraw
+// RUN: llvm-profdata show --all-functions --counts --text %t.normal.profdata > %t.normal.profdata.show
+
+// With -profile-correlate=binary flag
+// RUN: %clang -o %t-1.exe -fprofile-instr-generate -fcoverage-mapping -fcoverage-mcdc -mllvm -profile-correlate=binary %S/Inputs/instrprof-mcdc-correlation.cpp
+// RUN: env LLVM_PROFILE_FILE=%t-1.profraw %run %t-1.exe
+// RUN: llvm-profdata merge -o %t-1.profdata --binary-file=%t-1.exe %t-1.profraw
+// RUN: llvm-profdata show --all-functions --counts --text %t-1.profdata > %t-1.profdata.show
+
+// With -profile-correlate=debug-info flag
+// RUN: %clang -o %t-2.exe -fprofile-instr-generate -fcoverage-mapping -fcoverage-mcdc -mllvm -profile-correlate=debug-info -g %S/Inputs/instrprof-mcdc-correlation.cpp
+// RUN: env LLVM_PROFILE_FILE=%t-2.profraw %run %t-2.exe
+// RUN: llvm-profdata merge -o %t-2.profdata --debug-info=%t-2.exe %t-2.profraw
+// RUN: llvm-profdata show --all-functions --counts --text %t-2.profdata > %t-2.profdata.show
+
+// RUN: diff %t.normal.profdata.show %t-1.profdata.show
+// RUN: diff %t.normal.profdata.show %t-2.profdata.show

llvm/include/llvm/ProfileData/InstrProfCorrelator.h

@@ -68,6 +68,7 @@ class InstrProfCorrelator {
   static const char *FunctionNameAttributeName;
   static const char *CFGHashAttributeName;
   static const char *NumCountersAttributeName;
+  static const char *NumBitmapBitsAttributeName;
 
   enum InstrProfCorrelatorKind { CK_32Bit, CK_64Bit };
   InstrProfCorrelatorKind getKind() const { return Kind; }
@@ -82,6 +83,9 @@ class InstrProfCorrelator {
     /// The address range of the __llvm_prf_cnts section.
     uint64_t CountersSectionStart;
     uint64_t CountersSectionEnd;
+    /// The address range of the __llvm_prf_bits section.
+    uint64_t BitmapSectionStart;
+    uint64_t BitmapSectionEnd;
     /// The pointer points to start/end of profile data/name sections if
     /// FileKind is Binary.
     const char *DataStart;
@@ -104,7 +108,9 @@ class InstrProfCorrelator {
     std::optional<std::string> LinkageName;
     yaml::Hex64 CFGHash;
     yaml::Hex64 CounterOffset;
+    yaml::Hex64 BitmapOffset;
     uint32_t NumCounters;
+    uint32_t NumBitmapBytes;
     std::optional<std::string> FilePath;
     std::optional<int> LineNumber;
   };
@@ -158,8 +164,9 @@ class InstrProfCorrelatorImpl : public InstrProfCorrelator {
   Error dumpYaml(int MaxWarnings, raw_ostream &OS) override;
 
   void addDataProbe(uint64_t FunctionName, uint64_t CFGHash,
-                    IntPtrT CounterOffset, IntPtrT FunctionPtr,
-                    uint32_t NumCounters);
+                    IntPtrT CounterOffset, IntPtrT BitmapOffset,
+                    IntPtrT FunctionPtr, uint32_t NumCounters,
+                    uint32_t NumBitmapBytes);
 
   // Byte-swap the value if necessary.
   template <class T> T maybeSwap(T Value) const {
@@ -171,6 +178,7 @@ class InstrProfCorrelatorImpl : public InstrProfCorrelator {
                           std::unique_ptr<InstrProfCorrelator::Context> Ctx)
       : InstrProfCorrelator(Kind, std::move(Ctx)){};
   llvm::DenseSet<IntPtrT> CounterOffsets;
+  llvm::DenseSet<IntPtrT> BitmapOffsets;
 };
 
 /// DwarfInstrProfCorrelator - A child of InstrProfCorrelatorImpl that takes
@@ -190,8 +198,8 @@ class DwarfInstrProfCorrelator : public InstrProfCorrelatorImpl<IntPtrT> {
   std::optional<uint64_t> getLocation(const DWARFDie &Die) const;
 
   /// Returns true if the provided DIE symbolizes an instrumentation probe
-  /// symbol.
-  static bool isDIEOfProbe(const DWARFDie &Die);
+  /// symbol of the necessary type.
+  static bool isDIEOfProbe(const DWARFDie &Die, const StringRef &Prefix);
 
   /// Iterate over DWARF DIEs to find those that symbolize instrumentation
   /// probes and construct the ProfileData vector and Names string.

llvm/include/llvm/ProfileData/InstrProfReader.h

@@ -470,7 +470,8 @@ class RawInstrProfReader : public InstrProfReader {
   bool atEnd() const { return Data == DataEnd; }
 
   void advanceData() {
-    // `CountersDelta` is a constant zero when using debug info correlation.
+    // `CountersDelta` and `BitmapDelta` are constant zero when using debug info
+    // correlation.
     if (!Correlator && !BIDFetcherCorrelator) {
       // The initial CountersDelta is the in-memory address difference between
       // the data and counts sections: