[Coverage] Provide a stable order for getInstantiationGroups

[vsk]

Summary

This is a follow-up to r316490.

[mgrang]

LGTM.

llvm/trunk/lib/ProfileData/Coverage/CoverageMapping.cpp

 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/ManagedStatic.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
 #include <cassert>
 #include <cstdint>
 #include <iterator>
+#include <map>
 #include <memory>
 #include <string>
 #include <system_error>
 #include <utility>
 #include <vector>
 
 using namespace llvm;
 using namespace coverage;

 
 namespace {
 
 /// \brief Distributes functions into instantiation sets.
 ///
 /// An instantiation set is a collection of functions that have the same source
 /// code, ie, template functions specializations.
 class FunctionInstantiationSetCollector {
-  using MapT = DenseMap<LineColPair, std::vector<const FunctionRecord *>>;
+  using MapT = std::map<LineColPair, std::vector<const FunctionRecord *>>;
   MapT InstantiatedFunctions;
 
 public:
   void insert(const FunctionRecord &Function, unsigned FileID) {
     auto I = Function.CountedRegions.begin(), E = Function.CountedRegions.end();
     while (I != E && I->FileID != FileID)
       ++I;
     assert(I != E && "function does not cover the given file");