Index: include/llvm/Support/Timer.h
===================================================================
--- include/llvm/Support/Timer.h
+++ include/llvm/Support/Timer.h
@@ -62,8 +62,8 @@
     MemUsed    -= RHS.MemUsed;
   }
 
-  /// print - Print the current timer to standard error, and reset the "Started"
-  /// flag.
+  /// print - Print the current time record to \p OS, with a breakdown showing
+  /// contributions to the \p Total time record.
   void print(const TimeRecord &Total, raw_ostream &OS) const;
 };
 
@@ -76,9 +76,10 @@
 /// if they are never started.
 ///
 class Timer {
-  TimeRecord Time;
+  TimeRecord Time;       // The total time captured
+  TimeRecord StartTime;  // The time `startTimer' was last called
   std::string Name;      // The name of this time variable.
-  bool Started;          // Has this time variable ever been started?
+  bool Started;          // Is the timer currently running?
   TimerGroup *TG;        // The TimerGroup this Timer is in.
 
   Timer **Prev, *Next;   // Doubly linked list of timers in the group.
@@ -102,16 +103,24 @@
   const std::string &getName() const { return Name; }
   bool isInitialized() const { return TG != nullptr; }
 
-  /// startTimer - Start the timer running.  Time between calls to
-  /// startTimer/stopTimer is counted by the Timer class.  Note that these calls
-  /// must be correctly paired.
-  ///
+  /// hasTriggered - Check if startTimer() has ever been called on this timer.
+  bool hasTriggered() const { return TimeRecord() < StartTime; }
+
+  /// Start the timer running.  Time between calls to startTimer/stopTimer is
+  /// counted by the Timer class.  Note that these calls must be correctly
+  /// paired.
   void startTimer();
 
-  /// stopTimer - Stop the timer.
-  ///
+  /// Stop the timer.
   void stopTimer();
 
+  /// Stop the timer if it's running and clear the total time. This does not
+  /// affect the result of hasTriggered().
+  void clear();
+
+  /// Return the duration for which this timer has been running.
+  TimeRecord getTotalTime() const { return Time; }
+
 private:
   friend class TimerGroup;
 };
Index: lib/Support/Timer.cpp
===================================================================
--- lib/Support/Timer.cpp
+++ lib/Support/Timer.cpp
@@ -96,11 +96,7 @@
 //===----------------------------------------------------------------------===//
 
 void Timer::init(StringRef N) {
-  assert(!TG && "Timer already initialized");
-  Name.assign(N.begin(), N.end());
-  Started = false;
-  TG = getDefaultTimerGroup();
-  TG->addTimer(*this);
+  init(N, *getDefaultTimerGroup());
 }
 
 void Timer::init(StringRef N, TimerGroup &tg) {
@@ -139,25 +135,22 @@
   return Result;
 }
 
-static ManagedStatic<std::vector<Timer*> > ActiveTimers;
-
 void Timer::startTimer() {
+  assert(!Started && "Cannot start a running timer");
   Started = true;
-  ActiveTimers->push_back(this);
-  Time -= TimeRecord::getCurrentTime(true);
+  StartTime = TimeRecord::getCurrentTime(true);
 }
 
 void Timer::stopTimer() {
+  assert(Started && "Cannot stop a paused timer");
+  Started = false;
   Time += TimeRecord::getCurrentTime(false);
+  Time -= StartTime;
+}
 
-  if (ActiveTimers->back() == this) {
-    ActiveTimers->pop_back();
-  } else {
-    std::vector<Timer*>::iterator I =
-      std::find(ActiveTimers->begin(), ActiveTimers->end(), this);
-    assert(I != ActiveTimers->end() && "stop but no startTimer?");
-    ActiveTimers->erase(I);
-  }
+void Timer::clear() {
+  Started = false;
+  Time = TimeRecord();
 }
 
 static void printVal(double Val, double Total, raw_ostream &OS) {
@@ -275,8 +268,8 @@
   sys::SmartScopedLock<true> L(*TimerLock);
   
   // If the timer was started, move its data to TimersToPrint.
-  if (T.Started)
-    TimersToPrint.push_back(std::make_pair(T.Time, T.Name));
+  if (T.hasTriggered())
+    TimersToPrint.push_back(std::make_pair(T.getTotalTime(), T.getName()));
 
   T.TG = nullptr;
   
@@ -361,12 +354,11 @@
   // See if any of our timers were started, if so add them to TimersToPrint and
   // reset them.
   for (Timer *T = FirstTimer; T; T = T->Next) {
-    if (!T->Started) continue;
-    TimersToPrint.push_back(std::make_pair(T->Time, T->Name));
+    if (!T->hasTriggered()) continue;
+    TimersToPrint.push_back(std::make_pair(T->getTotalTime(), T->getName()));
     
     // Clear out the time.
-    T->Started = 0;
-    T->Time = TimeRecord();
+    T->clear();
   }
 
   // If any timers were started, print the group.