Index: lib/ProfileData/Coverage/CoverageMappingReader.cpp
===================================================================
--- lib/ProfileData/Coverage/CoverageMappingReader.cpp
+++ lib/ProfileData/Coverage/CoverageMappingReader.cpp
@@ -491,6 +491,13 @@
     return coveragemap_error::malformed;
   ProfileNames.create(Data.substr(0, ProfileNamesSize), Address);
   CoverageMapping = Data.substr(ProfileNamesSize);
+  // Skip the padding bytes because coverage map data has an alignment of 8.
+  if (CoverageMapping.size() < 1)
+    return coveragemap_error::malformed;
+  size_t Pad = alignmentAdjustment(CoverageMapping.data(), 8);
+  if (CoverageMapping.size() < Pad)
+    return coveragemap_error::malformed;
+  CoverageMapping = CoverageMapping.substr(Pad);
   return std::error_code();
 }
 
Index: tools/llvm-cov/TestingSupport.cpp
===================================================================
--- tools/llvm-cov/TestingSupport.cpp
+++ tools/llvm-cov/TestingSupport.cpp
@@ -88,7 +88,11 @@
   OS << "llvmcovmtestdata";
   encodeULEB128(ProfileNamesData.size(), OS);
   encodeULEB128(ProfileNamesAddress, OS);
-  OS << ProfileNamesData << CoverageMappingData;
+  OS << ProfileNamesData;
+  // Coverage mapping data is expected to have an alignment of 8.
+  for (unsigned Pad = OffsetToAlignment(OS.tell(), 8); Pad; --Pad)
+    OS.write(uint8_t(0));
+  OS << CoverageMappingData;
 
   return 0;
 }