[llvm-cov] Suppress sub-line highlights in simple cases

llvm-cov tends to highlight too many regions because its policy is to
highlight all region entry segments. This can look confusing to users:
not all region entry segments are interesting and deserve highlighting.
Emitting these highlights only when the region count differs from the
line count is a more user-friendly policy.

llvm-svn: 316109
diff --git a/llvm/tools/llvm-cov/SourceCoverageViewText.cpp b/llvm/tools/llvm-cov/SourceCoverageViewText.cpp
index 83d228e..2ed16df 100644
--- a/llvm/tools/llvm-cov/SourceCoverageViewText.cpp
+++ b/llvm/tools/llvm-cov/SourceCoverageViewText.cpp
@@ -186,6 +186,8 @@
   for (const auto *S : Segments) {
     if (!S->IsRegionEntry)
       continue;
+    if (S->Count == Line.getExecutionCount())
+      continue;
     // Skip to the new region.
     if (S->Col > PrevColumn)
       OS.indent(S->Col - PrevColumn);