Change the implementation of statistic to not need destructors at all.

Instead, the stat info is printed when llvm_shutdown() is called.
These also don't need static ctors, but getting rid of them is uglier:
still investigating.  This reduces the number of static dtors in llvm from
~1400 to ~750.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@32372 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/ADT/Statistic.h

@@ -31,29 +31,36 @@ namespace llvm {
 class Statistic {
   const char *Name;
   const char *Desc;
-  unsigned Value;
-  static unsigned NumStats;
+  unsigned Value : 31;
+  bool Initialized : 1;
 public:
   // Normal constructor, default initialize data item...
   Statistic(const char *name, const char *desc)
-    : Name(name), Desc(desc), Value(0) {
-    ++NumStats;  // Keep track of how many stats are created...
+    : Name(name), Desc(desc), Value(0), Initialized(0) {
   }
 
-  // Print information when destroyed, iff command line option is specified
-  ~Statistic();
-
-  // Allow use of this class as the value itself...
+  unsigned getValue() const { return Value; }
+  const char *getName() const { return Name; }
+  const char *getDesc() const { return Desc; }
+  
+  // Allow use of this class as the value itself.
   operator unsigned() const { return Value; }
-  const Statistic &operator=(unsigned Val) { Value = Val; return *this; }
-  const Statistic &operator++() { ++Value; return *this; }
-  unsigned operator++(int) { return Value++; }
-  const Statistic &operator--() { --Value; return *this; }
-  unsigned operator--(int) { return Value--; }
-  const Statistic &operator+=(const unsigned &V) { Value += V; return *this; }
-  const Statistic &operator-=(const unsigned &V) { Value -= V; return *this; }
-  const Statistic &operator*=(const unsigned &V) { Value *= V; return *this; }
-  const Statistic &operator/=(const unsigned &V) { Value /= V; return *this; }
+  const Statistic &operator=(unsigned Val) { Value = Val; return init(); }
+  const Statistic &operator++() { ++Value; return init(); }
+  unsigned operator++(int) { init(); return Value++; }
+  const Statistic &operator--() { --Value; return init(); }
+  unsigned operator--(int) { init(); return Value--; }
+  const Statistic &operator+=(const unsigned &V) { Value += V; return init(); }
+  const Statistic &operator-=(const unsigned &V) { Value -= V; return init(); }
+  const Statistic &operator*=(const unsigned &V) { Value *= V; return init(); }
+  const Statistic &operator/=(const unsigned &V) { Value /= V; return init(); }
+  
+private:
+  Statistic &init() {
+    if (!Initialized) RegisterStatistic();
+    return *this;
+  }
+  void RegisterStatistic();
 };
 
 } // End llvm namespace

lib/Support/Statistic.cpp

@@ -15,7 +15,7 @@
 // This is useful for reporting information like the number of instructions
 // simplified, optimized or removed by various transformations, like this:
 //
-// static Statistic NumInstEliminated("GCSE - Number of instructions killed");
+// static Statistic NumInstEliminated("GCSE", "Number of instructions killed");
 //
 // Later, in the code: ++NumInstEliminated;
 //
@@ -23,84 +23,99 @@
 
 #include "llvm/ADT/Statistic.h"
 #include "llvm/Support/CommandLine.h"
+#include "llvm/Support/ManagedStatic.h"
 #include "llvm/Support/Streams.h"
 #include "llvm/ADT/StringExtras.h"
 #include <algorithm>
 #include <ostream>
 using namespace llvm;
 
-// GetLibSupportInfoOutputFile - Return a file stream to print our output on...
+// GetLibSupportInfoOutputFile - Return a file stream to print our output on.
 namespace llvm { extern std::ostream *GetLibSupportInfoOutputFile(); }
 
-unsigned Statistic::NumStats = 0;
-
-// -stats - Command line option to cause transformations to emit stats about
-// what they did.
-//
+/// -stats - Command line option to cause transformations to emit stats about
+/// what they did.
+///
 static cl::opt<bool>
 Enabled("stats", cl::desc("Enable statistics output from program"));
 
-struct StatRecord {
-  std::string Value;
-  const char *Name, *Desc;
 
-  StatRecord(const std::string &V, const char *N, const char *D)
-    : Value(V), Name(N), Desc(D) {}
-
-  bool operator<(const StatRecord &SR) const {
-    return std::strcmp(Name, SR.Name) < 0;
+namespace {
+/// StatisticInfo - This class is used in a ManagedStatic so that it is created
+/// on demand (when the first statistic is bumped) and destroyed only when 
+/// llvm_shutdown is called.  We print statistics from the destructor.
+class StatisticInfo {
+  std::vector<const Statistic*> Stats;
+public:
+  ~StatisticInfo();
+  
+  void addStatistic(const Statistic *S) {
+    Stats.push_back(S);
   }
+};
+}
 
-  void print(unsigned ValFieldSize, unsigned NameFieldSize,
-             std::ostream &OS) {
-    OS << std::string(ValFieldSize-Value.length(), ' ')
-       << Value << " " << Name
-       << std::string(NameFieldSize-std::strlen(Name), ' ')
-       << " - " << Desc << "\n";
+static ManagedStatic<StatisticInfo> StatInfo;
+
+
+/// RegisterStatistic - The first time a statistic is bumped, this method is
+/// called.
+void Statistic::RegisterStatistic() {
+  // If stats are enabled, inform StatInfo that this statistic should be
+  // printed.
+  if (Enabled)
+    StatInfo->addStatistic(this);
+  // Remember we have been registered.
+  Initialized = true;
+}
+
+struct NameCompare {
+  bool operator()(const Statistic *LHS, const Statistic *RHS) const {
+    int Cmp = std::strcmp(LHS->getName(), RHS->getName());
+    if (Cmp != 0) return Cmp < 0;
+    
+    // Secondary key is the description.
+    return std::strcmp(LHS->getDesc(), RHS->getDesc()) < 0;
   }
 };
 
-static std::vector<StatRecord> *AccumStats = 0;
+// Print information when destroyed, iff command line option is specified.
+StatisticInfo::~StatisticInfo() {
+  // Statistics not enabled?
+  if (Stats.empty()) return;
 
-// Print information when destroyed, iff command line option is specified
-Statistic::~Statistic() {
-  if (Enabled && Value != 0) {
-    if (AccumStats == 0)
-      AccumStats = new std::vector<StatRecord>();
+  // Get the stream to write to.
+  std::ostream &OutStream = *GetLibSupportInfoOutputFile();
 
-    AccumStats->push_back(StatRecord(utostr(Value), Name, Desc));
+  // Figure out how long the biggest Value and Name fields are.
+  unsigned MaxNameLen = 0, MaxValLen = 0;
+  for (unsigned i = 0, e = Stats.size(); i != e; ++i) {
+    MaxValLen = std::max(MaxValLen,
+                         (unsigned)utostr(Stats[i]->getValue()).size());
+    MaxNameLen = std::max(MaxNameLen,
+                          (unsigned)std::strlen(Stats[i]->getName()));
   }
+  
+  // Sort the fields by name.
+  std::stable_sort(Stats.begin(), Stats.end(), NameCompare());
 
-  if (--NumStats == 0 && AccumStats) {
-    std::ostream *OutStream = GetLibSupportInfoOutputFile();
-
-    // Figure out how long the biggest Value and Name fields are...
-    unsigned MaxNameLen = 0, MaxValLen = 0;
-    for (unsigned i = 0, e = AccumStats->size(); i != e; ++i) {
-      MaxValLen = std::max(MaxValLen,
-                           (unsigned)(*AccumStats)[i].Value.length());
-      MaxNameLen = std::max(MaxNameLen,
-                            (unsigned)std::strlen((*AccumStats)[i].Name));
-    }
-
-    // Sort the fields...
-    std::stable_sort(AccumStats->begin(), AccumStats->end());
-
-    // Print out the statistics header...
-    *OutStream << "===" << std::string(73, '-') << "===\n"
-               << "                          ... Statistics Collected ...\n"
-               << "===" << std::string(73, '-') << "===\n\n";
-
-    // Print all of the statistics accumulated...
-    for (unsigned i = 0, e = AccumStats->size(); i != e; ++i)
-      (*AccumStats)[i].print(MaxValLen, MaxNameLen, *OutStream);
-
-    *OutStream << std::endl;  // Flush the output stream...
-
-    // Free all accumulated statistics...
-    delete AccumStats;
-    AccumStats = 0;
-    if (OutStream != cerr.stream() && OutStream != cout.stream())
-      delete OutStream;   // Close the file...
+  // Print out the statistics header...
+  OutStream << "===" << std::string(73, '-') << "===\n"
+            << "                          ... Statistics Collected ...\n"
+            << "===" << std::string(73, '-') << "===\n\n";
+  
+  // Print all of the statistics.
+  for (unsigned i = 0, e = Stats.size(); i != e; ++i) {
+    std::string CountStr = utostr(Stats[i]->getValue());
+    OutStream << std::string(MaxValLen-CountStr.size(), ' ')
+              << CountStr << " " << Stats[i]->getName()
+              << std::string(MaxNameLen-std::strlen(Stats[i]->getName()), ' ')
+              << " - " << Stats[i]->getDesc() << "\n";
+    
   }
+  
+  OutStream << std::endl;  // Flush the output stream...
+  
+  if (&OutStream != cerr.stream() && &OutStream != cout.stream())
+    delete &OutStream;   // Close the file.
 }