--- a/tools/llvm-cov/SourceCoverageView.cpp	Wed Feb 18 14:56:07 2015 +0900
+++ b/tools/llvm-cov/SourceCoverageView.cpp	Tue Oct 13 17:48:58 2015 +0900
@@ -14,6 +14,7 @@
 #include "SourceCoverageView.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/StringExtras.h"
 #include "llvm/Support/LineIterator.h"
 
 using namespace llvm;
@@ -77,6 +78,22 @@
     OS << "-";
 }
 
+/// Format a count using engineering notation with 3 significant digits.
+static std::string formatCount(uint64_t N) {
+  std::string Number = utostr(N);
+  int Len = Number.size();
+  if (Len <= 3)
+    return Number;
+  int IntLen = Len % 3 == 0 ? 3 : Len % 3;
+  std::string Result(Number.data(), IntLen);
+  if (IntLen != 3) {
+    Result.push_back('.');
+    Result += Number.substr(IntLen, 3 - IntLen);
+  }
+  Result.push_back(" kMGTPEZY"[(Len - 1) / 3]);
+  return Result;
+}
+
 void
 SourceCoverageView::renderLineCoverageColumn(raw_ostream &OS,
                                              const LineCoverageInfo &Line) {
@@ -84,17 +101,11 @@
     OS.indent(LineCoverageColumnWidth) << '|';
     return;
   }
-  SmallString<32> Buffer;
-  raw_svector_ostream BufferOS(Buffer);
-  BufferOS << Line.ExecutionCount;
-  auto Str = BufferOS.str();
-  // Trim
-  Str = Str.substr(0, std::min(Str.size(), (size_t)LineCoverageColumnWidth));
-  // Align to the right
-  OS.indent(LineCoverageColumnWidth - Str.size());
+  std::string C = formatCount(Line.ExecutionCount);
+  OS.indent(LineCoverageColumnWidth - C.size());
   colored_ostream(OS, raw_ostream::MAGENTA,
                   Line.hasMultipleRegions() && Options.Colors)
-      << Str;
+      << C;
   OS << '|';
 }
 
@@ -111,9 +122,6 @@
 
 void SourceCoverageView::renderRegionMarkers(
     raw_ostream &OS, ArrayRef<const coverage::CoverageSegment *> Segments) {
-  SmallString<32> Buffer;
-  raw_svector_ostream BufferOS(Buffer);
-
   unsigned PrevColumn = 1;
   for (const auto *S : Segments) {
     if (!S->IsRegionEntry)
@@ -122,20 +130,16 @@
     if (S->Col > PrevColumn)
       OS.indent(S->Col - PrevColumn);
     PrevColumn = S->Col + 1;
-    BufferOS << S->Count;
-    StringRef Str = BufferOS.str();
-    // Trim the execution count
-    Str = Str.substr(0, std::min(Str.size(), (size_t)7));
-    PrevColumn += Str.size();
-    OS << '^' << Str;
-    Buffer.clear();
+    std::string C = formatCount(S->Count);
+    PrevColumn += C.size();
+    OS << '^' << C;
   }
   OS << "\n";
 
   if (Options.Debug)
     for (const auto *S : Segments)
-      errs() << "Marker at " << S->Line << ":" << S->Col << " = " << S->Count
-             << (S->IsRegionEntry ? "\n" : " (pop)\n");
+      errs() << "Marker at " << S->Line << ":" << S->Col << " = "
+             << formatCount(S->Count) << (S->IsRegionEntry ? "\n" : " (pop)\n");
 }
 
 void SourceCoverageView::render(raw_ostream &OS, bool WholeFile,