[Stats] Clear all timers on print, since they stopped self-clearing recently.

Author: graydon

lib/Basic/Statistic.cpp

@@ -444,6 +444,7 @@ UnifiedStatsReporter::printAlwaysOnStatsAndTimers(raw_ostream &OS) {
   }
   // Print timers.
   TimerGroup::printAllJSONValues(OS, delim);
+  TimerGroup::clearAll();
   OS << "\n}\n";
   OS.flush();
 }
@@ -664,6 +665,7 @@ UnifiedStatsReporter::~UnifiedStatsReporter()
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_STATS)
   publishAlwaysOnStatsToLLVM();
   PrintStatisticsJSON(ostream);
+  TimerGroup::clearAll();
 #else
   printAlwaysOnStatsAndTimers(ostream);
 #endif

test/Misc/stats_dir.swift

@@ -24,13 +24,16 @@
 // RUN: %{python} %utils/process-stats-dir.py --compare-to-csv-baseline %t/driver.csv %t
 
 // RUN: %target-swiftc_driver -c -o %t/out.o -stats-output-dir %t/this/is/not/a/directory %s 2>&1 | %FileCheck -check-prefix=CHECK-NODIR %s
+// RUN: %target-swiftc_driver -c -o %t/out.o -stats-output-dir %t %s 2>&1 | %FileCheck -allow-empty -check-prefix=CHECK-SILENT %s
 
 // CHECK: {{"AST.NumSourceLines"	[1-9][0-9]*$}}
 // CHECK: {{"IRModule.NumIRFunctions"	[1-9][0-9]*$}}
 // CHECK: {{"LLVM.NumLLVMBytesOutput"	[1-9][0-9]*$}}
 
 // CHECK-NODIR: {{Error opening -stats-output-dir file}}
 
+// CHECK-SILENT-NOT: {{---}}
+
 public func foo() {
     print("hello")
 }