Use atomic operations when accessing statistics, and make the lazy initialization of statistics actually threadsafe.

llvm-svn: 74005

llvm/include/llvm/ADT/Statistic.h

@@ -26,14 +26,16 @@
 #ifndef LLVM_ADT_STATISTIC_H
 #define LLVM_ADT_STATISTIC_H
 
+#include "llvm/System/Atomic.h"
+
 namespace llvm {
 
 class Statistic {
 public:
   const char *Name;
   const char *Desc;
-  unsigned Value : 31;
-  bool Initialized : 1;
+  unsigned Value;
+  bool Initialized;
 
   unsigned getValue() const { return Value; }
   const char *getName() const { return Name; }
@@ -47,19 +49,60 @@ public:
 
   // Allow use of this class as the value itself.
   operator unsigned() const { return Value; }
-  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(); }
+  const Statistic &operator=(unsigned Val) {
+    Value = Val;
+    return init();
+  }
+  
+  const Statistic &operator++() {
+    sys::AtomicIncrement(&Value);
+    return init();
+  }
+  
+  unsigned operator++(int) {
+    init();
+    unsigned OldValue = Value;
+    sys::AtomicIncrement(&Value);
+    return OldValue;
+  }
+  
+  const Statistic &operator--() {
+    sys::AtomicDecrement(&Value);
+    return init();
+  }
+  
+  unsigned operator--(int) {
+    init();
+    unsigned OldValue = Value;
+    sys::AtomicDecrement(&Value);
+    return OldValue;
+  }
+  
+  const Statistic &operator+=(const unsigned &V) {
+    sys::AtomicAdd(&Value, V);
+    return init();
+  }
+  
+  const Statistic &operator-=(const unsigned &V) {
+    sys::AtomicAdd(&Value, -V);
+    return init();
+  }
+  
+  const Statistic &operator*=(const unsigned &V) {
+    sys::AtomicMul(&Value, V);
+    return init();
+  }
+  
+  const Statistic &operator/=(const unsigned &V) {
+    sys::AtomicDiv(&Value, V);
+    return init();
+  }
 
 protected:
   Statistic &init() {
-    if (!Initialized) RegisterStatistic();
+    bool tmp = Initialized;
+    sys::MemoryFence();
+    if (!tmp) RegisterStatistic();
     return *this;
   }
   void RegisterStatistic();

llvm/lib/Support/Statistic.cpp

@@ -66,10 +66,14 @@ void Statistic::RegisterStatistic() {
   // If stats are enabled, inform StatInfo that this statistic should be
   // printed.
   sys::ScopedLock Writer(&*StatLock);
-  if (Enabled)
-    StatInfo->addStatistic(this);
-  // Remember we have been registered.
-  Initialized = true;
+  if (!Initialized) {
+    if (Enabled)
+      StatInfo->addStatistic(this);
+    
+    sys::MemoryFence();
+    // Remember we have been registered.
+    Initialized = true;
+  }
 }
 
 namespace {