[Support] Introduce a function to reset all debug counters (#194864)

This PR adds a function to reset all debug counters, and extends the
unit test to verify that the debug counters are reset as expected. This
is required for running tools repeatedly in the same process.

llvm/include/llvm/Support/DebugCounter.h

@@ -78,6 +78,14 @@ public:
     CounterInfo(StringRef Name, StringRef Desc) : Name(Name), Desc(Desc) {
       DebugCounter::registerCounter(this);
     }
+
+    void reset() {
+      Active = false;
+      IsSet = false;
+      Count = 0;
+      CurrChunkIdx = 0;
+      Chunks.clear();
+    }
   };
 
   LLVM_ABI static void
@@ -165,6 +173,11 @@ public:
       Counter->Active = true;
   }
 
+  void resetAllCounters() {
+    for (auto &[_, Counter] : Counters)
+      Counter->reset();
+  }
+
 protected:
   void addCounter(CounterInfo *Info) { Counters[Info->Name] = Info; }
   bool handleCounterIncrement(CounterInfo &Info);

llvm/unittests/Support/DebugCounterTest.cpp

@@ -35,6 +35,19 @@ TEST(DebugCounterTest, Basic) {
   llvm::raw_string_ostream OS(Str);
   DC->print(OS);
   EXPECT_TRUE(StringRef(Str).contains("{200,1:3-5:78:79:89:100-102:150}"));
+
+  DC->resetAllCounters();
+
+  // After resetting, counter is no longer set.
+  EXPECT_FALSE(DebugCounter::isCounterSet(TestCounter));
+
+  DC->push_back("test-counter=1");
+  EXPECT_TRUE(DebugCounter::isCounterSet(TestCounter));
+  EXPECT_EQ(DC->getCounterState(TestCounter).Count, 0);
+
+  DC->shouldExecute(TestCounter);
+
+  EXPECT_EQ(DC->getCounterState(TestCounter).Count, 1);
 }
 
 #endif