[Coverage] Add support for Branch Coverage in LLVM Source-Based Code Coverage

This is an enhancement to LLVM Source-Based Code Coverage in clang to track how
many times individual branch-generating conditions are taken (evaluate to TRUE)
and not taken (evaluate to FALSE).  Individual conditions may comprise larger
boolean expressions using boolean logical operators.  This functionality is
very similar to what is supported by GCOV except that it is very closely
anchored to the ASTs.

Differential Revision: https://reviews.llvm.org/D84467

1 files changed, 30 insertions, 6 deletions

diff --git a/llvm/lib/ProfileData/Coverage/CoverageMappingReader.cpp b/llvm/lib/ProfileData/Coverage/CoverageMappingReader.cpp
index 4936638..1acdcb4 100644
--- a/llvm/lib/ProfileData/Coverage/CoverageMappingReader.cpp
+++ b/llvm/lib/ProfileData/Coverage/CoverageMappingReader.cpp
@@ -213,7 +213,7 @@ Error RawCoverageMappingReader::readMappingRegionsSubArray(
     return Err;
   unsigned LineStart = 0;
   for (size_t I = 0; I < NumRegions; ++I) {
-    Counter C;
+    Counter C, C2;
     CounterMappingRegion::RegionKind Kind = CounterMappingRegion::CodeRegion;
 
     // Read the combined counter + region kind.
@@ -223,6 +223,18 @@ Error RawCoverageMappingReader::readMappingRegionsSubArray(
       return Err;
     unsigned Tag = EncodedCounterAndRegion & Counter::EncodingTagMask;
     uint64_t ExpandedFileID = 0;
+
+    // If Tag does not represent a ZeroCounter, then it is understood to refer
+    // to a counter or counter expression with region kind assumed to be
+    // "CodeRegion". In that case, EncodedCounterAndRegion actually encodes the
+    // referenced counter or counter expression (and nothing else).
+    //
+    // If Tag represents a ZeroCounter and EncodingExpansionRegionBit is set,
+    // then EncodedCounterAndRegion is interpreted to represent an
+    // ExpansionRegion. In all other cases, EncodedCounterAndRegion is
+    // interpreted to refer to a specific region kind, after which additional
+    // fields may be read (e.g. BranchRegions have two encoded counters that
+    // follow an encoded region kind value).
     if (Tag != Counter::Zero) {
       if (auto Err = decodeCounter(EncodedCounterAndRegion, C))
         return Err;
@@ -243,6 +255,14 @@ Error RawCoverageMappingReader::readMappingRegionsSubArray(
         case CounterMappingRegion::SkippedRegion:
           Kind = CounterMappingRegion::SkippedRegion;
           break;
+        case CounterMappingRegion::BranchRegion:
+          // For a Branch Region, read two successive counters.
+          Kind = CounterMappingRegion::BranchRegion;
+          if (auto Err = readCounter(C))
+            return Err;
+          if (auto Err = readCounter(C2))
+            return Err;
+          break;
         default:
           return make_error<CoverageMapError>(coveragemap_error::malformed);
         }
@@ -294,7 +314,7 @@ Error RawCoverageMappingReader::readMappingRegionsSubArray(
       dbgs() << "\n";
     });
 
-    auto CMR = CounterMappingRegion(C, InferredFileID, ExpandedFileID,
+    auto CMR = CounterMappingRegion(C, C2, InferredFileID, ExpandedFileID,
                                     LineStart, ColumnStart,
                                     LineStart + NumLines, ColumnEnd, Kind);
     if (CMR.startLoc() > CMR.endLoc())
@@ -600,7 +620,7 @@ public:
     CovBuf += FilenamesSize;
     FilenameRange FileRange(FilenamesBegin, Filenames.size() - FilenamesBegin);
 
-    if (Version == CovMapVersion::Version4) {
+    if (Version >= CovMapVersion::Version4) {
       // Map a hash of the filenames region to the filename range associated
       // with this coverage header.
       int64_t FilenamesRef =
@@ -628,7 +648,7 @@ public:
     // This is a no-op in Version4 (coverage mappings are not affixed to the
     // coverage header).
     const char *MappingBuf = CovBuf;
-    if (Version == CovMapVersion::Version4 && CoverageSize != 0)
+    if (Version >= CovMapVersion::Version4 && CoverageSize != 0)
       return make_error<CoverageMapError>(coveragemap_error::malformed);
     CovBuf += CoverageSize;
     const char *MappingEnd = CovBuf;
@@ -682,7 +702,7 @@ public:
       if (FileRange && !FileRange->isInvalid()) {
         StringRef Mapping =
             CFR->template getCoverageMapping<Endian>(OutOfLineMappingBuf);
-        if (Version == CovMapVersion::Version4 &&
+        if (Version >= CovMapVersion::Version4 &&
             Mapping.data() + Mapping.size() > FuncRecBufEnd)
           return make_error<CoverageMapError>(coveragemap_error::malformed);
         if (Error Err = insertFunctionRecordIfNeeded(CFR, Mapping, *FileRange))
@@ -711,6 +731,7 @@ Expected<std::unique_ptr<CovMapFuncRecordReader>> CovMapFuncRecordReader::get(
   case CovMapVersion::Version2:
   case CovMapVersion::Version3:
   case CovMapVersion::Version4:
+  case CovMapVersion::Version5:
     // Decompress the name data.
     if (Error E = P.create(P.getNameData()))
       return std::move(E);
@@ -723,6 +744,9 @@ Expected<std::unique_ptr<CovMapFuncRecordReader>> CovMapFuncRecordReader::get(
     else if (Version == CovMapVersion::Version4)
       return std::make_unique<VersionedCovMapFuncRecordReader<
           CovMapVersion::Version4, IntPtrT, Endian>>(P, R, F);
+    else if (Version == CovMapVersion::Version5)
+      return std::make_unique<VersionedCovMapFuncRecordReader<
+          CovMapVersion::Version5, IntPtrT, Endian>>(P, R, F);
   }
   llvm_unreachable("Unsupported version");
 }
@@ -766,7 +790,7 @@ static Error readCoverageMappingData(
   }
   // In Version4, function records are not affixed to coverage headers. Read
   // the records from their dedicated section.
-  if (Version == CovMapVersion::Version4)
+  if (Version >= CovMapVersion::Version4)
     return Reader->readFunctionRecords(FuncRecBuf, FuncRecBufEnd, None, nullptr,
                                        nullptr);
   return Error::success();