Coverage: add HasCodeBefore flag to a mapping region.

This flag will be used by the coverage tool to help 
compute the execution counts for each line in a source file.

Differential Revision: http://reviews.llvm.org/D4746

llvm-svn: 214740
diff --git a/llvm/lib/ProfileData/CoverageMappingReader.cpp b/llvm/lib/ProfileData/CoverageMappingReader.cpp
index c58df0f..c8108d4 100644
--- a/llvm/lib/ProfileData/CoverageMappingReader.cpp
+++ b/llvm/lib/ProfileData/CoverageMappingReader.cpp
@@ -170,13 +170,17 @@
     }
 
     // Read the source range.
-    uint64_t LineStartDelta, ColumnStart, NumLines, ColumnEnd;
+    uint64_t LineStartDelta, CodeBeforeColumnStart, NumLines, ColumnEnd;
     if (auto Err =
             readIntMax(LineStartDelta, std::numeric_limits<unsigned>::max()))
       return Err;
-    if (auto Err =
-            readIntMax(ColumnStart, std::numeric_limits<unsigned>::max()))
+    if (auto Err = readULEB128(CodeBeforeColumnStart))
       return Err;
+    bool HasCodeBefore = CodeBeforeColumnStart & 1;
+    uint64_t ColumnStart = CodeBeforeColumnStart >>
+                           CounterMappingRegion::EncodingHasCodeBeforeBits;
+    if (ColumnStart > std::numeric_limits<unsigned>::max())
+      return error(instrprof_error::malformed);
     if (auto Err = readIntMax(NumLines, std::numeric_limits<unsigned>::max()))
       return Err;
     if (auto Err = readIntMax(ColumnEnd, std::numeric_limits<unsigned>::max()))
@@ -194,9 +198,9 @@
       ColumnStart = 1;
       ColumnEnd = std::numeric_limits<unsigned>::max();
     }
-    MappingRegions.push_back(
-        CounterMappingRegion(C, InferredFileID, LineStart, ColumnStart,
-                             LineStart + NumLines, ColumnEnd, Kind));
+    MappingRegions.push_back(CounterMappingRegion(
+        C, InferredFileID, LineStart, ColumnStart, LineStart + NumLines,
+        ColumnEnd, HasCodeBefore, Kind));
     MappingRegions.back().ExpandedFileID = ExpandedFileID;
   }
   return success();