commit 1087a542554ac0ab23bbca07d026b2fb49862809
author Daniel Sanders <daniel_l_sanders@apple.com> Thu Mar 08 02:36:25 2018 +0000
committer Daniel Sanders <daniel_l_sanders@apple.com> Thu Mar 08 02:36:25 2018 +0000
tree e930be6193658e4dfbcfb9d91aabaa66799d1fbb
parent e4f47b4c63dd99508410087f5b6643f3e668ed23

Support resetting STATISTIC() values using llvm::ResetStatistics()

Summary:
Most of the time, compiler statistics can be obtained using a process that
performs a single compilation and terminates such as llc. However, this isn't
always the case. JITs for example, perform multiple compilations over their
lifetime and STATISTIC() will record cumulative values across all of them.

Provide tools like this with the facilities needed to measure individual
compilations by allowing them to reset the STATISTIC() values back to zero using
llvm::ResetStatistics(). It's still the tools responsibility to ensure that they
perform compilations in such a way that the results are meaningful to their
intended use.

Reviewers: qcolombet, rtereshin, bogner, aditya_nandakumar

Reviewed By: bogner

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D44181

llvm-svn: 326981

llvm/lib/Support/Statistic.cpp

diff --git a/llvm/lib/Support/Statistic.cpp b/llvm/lib/Support/Statistic.cpp
index 1985409..3f54374 100644
--- a/llvm/lib/Support/Statistic.cpp
+++ b/llvm/lib/Support/Statistic.cpp
@@ -58,7 +58,7 @@
 /// This class is also used to look up statistic values from applications that
 /// use LLVM.
 class StatisticInfo {
-  std::vector<const Statistic*> Stats;
+  std::vector<Statistic*> Stats;
 
   friend void llvm::PrintStatistics();
   friend void llvm::PrintStatistics(raw_ostream &OS);
@@ -67,12 +67,12 @@
   /// Sort statistics by debugtype,name,description.
   void sort();
 public:
-  using const_iterator = std::vector<const Statistic *>::const_iterator;
+  using const_iterator = std::vector<Statistic *>::const_iterator;
 
   StatisticInfo();
   ~StatisticInfo();
 
-  void addStatistic(const Statistic *S) {
+  void addStatistic(Statistic *S) {
     Stats.push_back(S);
   }
 
@@ -81,6 +81,8 @@
   iterator_range<const_iterator> statistics() const {
     return {begin(), end()};
   }
+
+  void reset();
 };
 } // end anonymous namespace
 
@@ -135,6 +137,28 @@
   });
 }
 
+void StatisticInfo::reset() {
+  sys::SmartScopedLock<true> Writer(*StatLock);
+
+  // Tell each statistic that it isn't registered so it has to register
+  // again. We're holding the lock so it won't be able to do so until we're
+  // finished. Once we've forced it to re-register (after we return), then zero
+  // the value.
+  for (auto *Stat : Stats) {
+    // Value updates to a statistic that complete before this statement in the
+    // iteration for that statistic will be lost as intended.
+    Stat->Initialized = false;
+    Stat->Value = 0;
+  }
+
+  // Clear the registration list and release the lock once we're done. Any
+  // pending updates from other threads will safely take effect after we return.
+  // That might not be what the user wants if they're measuring a compilation
+  // but it's their responsibility to prevent concurrent compilations to make
+  // a single compilation measurable.
+  Stats.clear();
+}
+
 void llvm::PrintStatistics(raw_ostream &OS) {
   StatisticInfo &Stats = *StatInfo;
 
@@ -227,3 +251,7 @@
     ReturnStats.emplace_back(Stat->getName(), Stat->getValue());
   return ReturnStats;
 }
+
+void llvm::ResetStatistics() {
+  StatInfo->reset();
+}