coverage: remove empty mapping regions

This patch removes the empty coverage mapping regions.
Those regions were produced by clang's old mapping region generation 
algorithm, but the new algorithm doesn't generate them.

llvm-svn: 213981

llvm/include/llvm/ProfileData/CoverageMapping.h

@@ -139,10 +139,6 @@ struct CounterMappingRegion {
     /// such as for a macro instantiation or #include file.
     ExpansionRegion,
 
-    /// \brief An EmptyRegion represents a source range without code,
-    /// but with a distinct counter.
-    EmptyRegion,
-
     /// \brief A SkippedRegion represents a source range with code that
     /// was skipped by a preprocessor or similar means.
     SkippedRegion

llvm/lib/ProfileData/CoverageMappingReader.cpp

@@ -160,9 +160,6 @@ std::error_code RawCoverageMappingReader::readMappingRegionsSubArray(
         case CounterMappingRegion::CodeRegion:
           // Don't do anything when we have a code region with a zero counter.
           break;
-        case CounterMappingRegion::EmptyRegion:
-          Kind = CounterMappingRegion::EmptyRegion;
-          break;
         case CounterMappingRegion::SkippedRegion:
           Kind = CounterMappingRegion::SkippedRegion;
           break;

llvm/lib/ProfileData/CoverageMappingWriter.cpp

@@ -172,11 +172,6 @@ void CoverageMappingWriter::write(raw_ostream &OS) {
       encodeULEB128(EncodedTagExpandedFileID, OS);
       break;
     }
-    case CounterMappingRegion::EmptyRegion:
-      encodeULEB128(unsigned(I.Kind)
-                        << Counter::EncodingCounterTagAndExpansionRegionTagBits,
-                    OS);
-      break;
     case CounterMappingRegion::SkippedRegion:
       assert(Count.isZero());
       encodeULEB128(unsigned(I.Kind)