InstrProf: Use a locally tracked current count in ComputeRegionCounts

No functional change. This just makes it more obvious that the logic
in ComputeRegionCounts only depends on the counter map and local
state.

llvm-svn: 236370

2 files changed, 35 insertions, 38 deletions

diff --git a/clang/lib/CodeGen/CodeGenPGO.cpp b/clang/lib/CodeGen/CodeGenPGO.cpp
index d9016774fa1..158a6ac17ba 100644
--- a/clang/lib/CodeGen/CodeGenPGO.cpp
+++ b/clang/lib/CodeGen/CodeGenPGO.cpp
@@ -242,6 +242,9 @@ struct ComputeRegionCounts : public ConstStmtVisitor<ComputeRegionCounts> {
   /// next statement, such as at the exit of a loop.
   bool RecordNextStmtCount;
 
+  /// The count at the current location in the traversal.
+  uint64_t CurrentCount;
+
   /// The map of statements to count values.
   llvm::DenseMap<const Stmt *, uint64_t> &CountMap;
 
@@ -259,14 +262,14 @@ struct ComputeRegionCounts : public ConstStmtVisitor<ComputeRegionCounts> {
 
   void RecordStmtCount(const Stmt *S) {
     if (RecordNextStmtCount) {
-      CountMap[S] = PGO.getCurrentRegionCount();
+      CountMap[S] = CurrentCount;
       RecordNextStmtCount = false;
     }
   }
 
   /// Set and return the current count.
   uint64_t setCount(uint64_t Count) {
-    PGO.setCurrentRegionCount(Count);
+    CurrentCount = Count;
     return Count;
   }
 
@@ -315,7 +318,7 @@ struct ComputeRegionCounts : public ConstStmtVisitor<ComputeRegionCounts> {
     RecordStmtCount(S);
     if (S->getRetValue())
       Visit(S->getRetValue());
-    PGO.setCurrentRegionUnreachable();
+    CurrentCount = 0;
     RecordNextStmtCount = true;
   }
 
@@ -323,13 +326,13 @@ struct ComputeRegionCounts : public ConstStmtVisitor<ComputeRegionCounts> {
     RecordStmtCount(E);
     if (E->getSubExpr())
       Visit(E->getSubExpr());
-    PGO.setCurrentRegionUnreachable();
+    CurrentCount = 0;
     RecordNextStmtCount = true;
   }
 
   void VisitGotoStmt(const GotoStmt *S) {
     RecordStmtCount(S);
-    PGO.setCurrentRegionUnreachable();
+    CurrentCount = 0;
     RecordNextStmtCount = true;
   }
 
@@ -344,30 +347,30 @@ struct ComputeRegionCounts : public ConstStmtVisitor<ComputeRegionCounts> {
   void VisitBreakStmt(const BreakStmt *S) {
     RecordStmtCount(S);
     assert(!BreakContinueStack.empty() && "break not in a loop or switch!");
-    BreakContinueStack.back().BreakCount += PGO.getCurrentRegionCount();
-    PGO.setCurrentRegionUnreachable();
+    BreakContinueStack.back().BreakCount += CurrentCount;
+    CurrentCount = 0;
     RecordNextStmtCount = true;
   }
 
   void VisitContinueStmt(const ContinueStmt *S) {
     RecordStmtCount(S);
     assert(!BreakContinueStack.empty() && "continue stmt not in a loop!");
-    BreakContinueStack.back().ContinueCount += PGO.getCurrentRegionCount();
-    PGO.setCurrentRegionUnreachable();
+    BreakContinueStack.back().ContinueCount += CurrentCount;
+    CurrentCount = 0;
     RecordNextStmtCount = true;
   }
 
   void VisitWhileStmt(const WhileStmt *S) {
     RecordStmtCount(S);
-    uint64_t ParentCount = PGO.getCurrentRegionCount();
+    uint64_t ParentCount = CurrentCount;
 
     BreakContinueStack.push_back(BreakContinue());
     // Visit the body region first so the break/continue adjustments can be
     // included when visiting the condition.
     uint64_t BodyCount = setCount(PGO.getRegionCount(S));
-    CountMap[S->getBody()] = PGO.getCurrentRegionCount();
+    CountMap[S->getBody()] = CurrentCount;
     Visit(S->getBody());
-    uint64_t BackedgeCount = PGO.getCurrentRegionCount();
+    uint64_t BackedgeCount = CurrentCount;
 
     // ...then go back and propagate counts through the condition. The count
     // at the start of the condition is the sum of the incoming edges,
@@ -388,10 +391,10 @@ struct ComputeRegionCounts : public ConstStmtVisitor<ComputeRegionCounts> {
 
     BreakContinueStack.push_back(BreakContinue());
     // The count doesn't include the fallthrough from the parent scope. Add it.
-    uint64_t BodyCount = setCount(LoopCount + PGO.getCurrentRegionCount());
+    uint64_t BodyCount = setCount(LoopCount + CurrentCount);
     CountMap[S->getBody()] = BodyCount;
     Visit(S->getBody());
-    uint64_t BackedgeCount = PGO.getCurrentRegionCount();
+    uint64_t BackedgeCount = CurrentCount;
 
     BreakContinue BC = BreakContinueStack.pop_back_val();
     // The count at the start of the condition is equal to the count at the
@@ -408,7 +411,7 @@ struct ComputeRegionCounts : public ConstStmtVisitor<ComputeRegionCounts> {
     if (S->getInit())
       Visit(S->getInit());
 
-    uint64_t ParentCount = PGO.getCurrentRegionCount();
+    uint64_t ParentCount = CurrentCount;
 
     BreakContinueStack.push_back(BreakContinue());
     // Visit the body region first. (This is basically the same as a while
@@ -416,7 +419,7 @@ struct ComputeRegionCounts : public ConstStmtVisitor<ComputeRegionCounts> {
     uint64_t BodyCount = setCount(PGO.getRegionCount(S));
     CountMap[S->getBody()] = BodyCount;
     Visit(S->getBody());
-    uint64_t BackedgeCount = PGO.getCurrentRegionCount();
+    uint64_t BackedgeCount = CurrentCount;
     BreakContinue BC = BreakContinueStack.pop_back_val();
 
     // The increment is essentially part of the body but it needs to include
@@ -444,15 +447,14 @@ struct ComputeRegionCounts : public ConstStmtVisitor<ComputeRegionCounts> {
     Visit(S->getRangeStmt());
     Visit(S->getBeginEndStmt());
 
-    uint64_t ParentCount = PGO.getCurrentRegionCount();
-
+    uint64_t ParentCount = CurrentCount;
     BreakContinueStack.push_back(BreakContinue());
     // Visit the body region first. (This is basically the same as a while
     // loop; see further comments in VisitWhileStmt.)
     uint64_t BodyCount = setCount(PGO.getRegionCount(S));
     CountMap[S->getBody()] = BodyCount;
     Visit(S->getBody());
-    uint64_t BackedgeCount = PGO.getCurrentRegionCount();
+    uint64_t BackedgeCount = CurrentCount;
     BreakContinue BC = BreakContinueStack.pop_back_val();
 
     // The increment is essentially part of the body but it needs to include
@@ -473,13 +475,13 @@ struct ComputeRegionCounts : public ConstStmtVisitor<ComputeRegionCounts> {
   void VisitObjCForCollectionStmt(const ObjCForCollectionStmt *S) {
     RecordStmtCount(S);
     Visit(S->getElement());
-    uint64_t ParentCount = PGO.getCurrentRegionCount();
+    uint64_t ParentCount = CurrentCount;
     BreakContinueStack.push_back(BreakContinue());
     // Counter tracks the body of the loop.
     uint64_t BodyCount = setCount(PGO.getRegionCount(S));
     CountMap[S->getBody()] = BodyCount;
     Visit(S->getBody());
-    uint64_t BackedgeCount = PGO.getCurrentRegionCount();
+    uint64_t BackedgeCount = CurrentCount;
     BreakContinue BC = BreakContinueStack.pop_back_val();
 
     setCount(BC.BreakCount + ParentCount + BackedgeCount + BC.ContinueCount -
@@ -490,7 +492,7 @@ struct ComputeRegionCounts : public ConstStmtVisitor<ComputeRegionCounts> {
   void VisitSwitchStmt(const SwitchStmt *S) {
     RecordStmtCount(S);
     Visit(S->getCond());
-    PGO.setCurrentRegionUnreachable();
+    CurrentCount = 0;
     BreakContinueStack.push_back(BreakContinue());
     Visit(S->getBody());
     // If the switch is inside a loop, add the continue counts.
@@ -508,7 +510,7 @@ struct ComputeRegionCounts : public ConstStmtVisitor<ComputeRegionCounts> {
     // switch header and does not include fallthrough from the case before
     // this one.
     uint64_t CaseCount = PGO.getRegionCount(S);
-    setCount(PGO.getCurrentRegionCount() + CaseCount);
+    setCount(CurrentCount + CaseCount);
     // We need the count without fallthrough in the mapping, so it's more useful
     // for branch probabilities.
     CountMap[S] = CaseCount;
@@ -518,7 +520,7 @@ struct ComputeRegionCounts : public ConstStmtVisitor<ComputeRegionCounts> {
 
   void VisitIfStmt(const IfStmt *S) {
     RecordStmtCount(S);
-    uint64_t ParentCount = PGO.getCurrentRegionCount();
+    uint64_t ParentCount = CurrentCount;
     Visit(S->getCond());
 
     // Counter tracks the "then" part of an if statement. The count for
@@ -526,14 +528,14 @@ struct ComputeRegionCounts : public ConstStmtVisitor<ComputeRegionCounts> {
     uint64_t ThenCount = setCount(PGO.getRegionCount(S));
     CountMap[S->getThen()] = ThenCount;
     Visit(S->getThen());
-    uint64_t OutCount = PGO.getCurrentRegionCount();
+    uint64_t OutCount = CurrentCount;
 
     uint64_t ElseCount = ParentCount - ThenCount;
     if (S->getElse()) {
       setCount(ElseCount);
       CountMap[S->getElse()] = ElseCount;
       Visit(S->getElse());
-      OutCount += PGO.getCurrentRegionCount();
+      OutCount += CurrentCount;
     } else
       OutCount += ElseCount;
     setCount(OutCount);
@@ -560,7 +562,7 @@ struct ComputeRegionCounts : public ConstStmtVisitor<ComputeRegionCounts> {
 
   void VisitAbstractConditionalOperator(const AbstractConditionalOperator *E) {
     RecordStmtCount(E);
-    uint64_t ParentCount = PGO.getCurrentRegionCount();
+    uint64_t ParentCount = CurrentCount;
     Visit(E->getCond());
 
     // Counter tracks the "true" part of a conditional operator. The
@@ -568,12 +570,12 @@ struct ComputeRegionCounts : public ConstStmtVisitor<ComputeRegionCounts> {
     uint64_t TrueCount = setCount(PGO.getRegionCount(E));
     CountMap[E->getTrueExpr()] = TrueCount;
     Visit(E->getTrueExpr());
-    uint64_t OutCount = PGO.getCurrentRegionCount();
+    uint64_t OutCount = CurrentCount;
 
     uint64_t FalseCount = setCount(ParentCount - TrueCount);
     CountMap[E->getFalseExpr()] = FalseCount;
     Visit(E->getFalseExpr());
-    OutCount += PGO.getCurrentRegionCount();
+    OutCount += CurrentCount;
 
     setCount(OutCount);
     RecordNextStmtCount = true;
@@ -581,25 +583,25 @@ struct ComputeRegionCounts : public ConstStmtVisitor<ComputeRegionCounts> {
 
   void VisitBinLAnd(const BinaryOperator *E) {
     RecordStmtCount(E);
-    uint64_t ParentCount = PGO.getCurrentRegionCount();
+    uint64_t ParentCount = CurrentCount;
     Visit(E->getLHS());
     // Counter tracks the right hand side of a logical and operator.
     uint64_t RHSCount = setCount(PGO.getRegionCount(E));
     CountMap[E->getRHS()] = RHSCount;
     Visit(E->getRHS());
-    setCount(ParentCount + RHSCount - PGO.getCurrentRegionCount());
+    setCount(ParentCount + RHSCount - CurrentCount);
     RecordNextStmtCount = true;
   }
 
   void VisitBinLOr(const BinaryOperator *E) {
     RecordStmtCount(E);
-    uint64_t ParentCount = PGO.getCurrentRegionCount();
+    uint64_t ParentCount = CurrentCount;
     Visit(E->getLHS());
     // Counter tracks the right hand side of a logical or operator.
     uint64_t RHSCount = setCount(PGO.getRegionCount(E));
     CountMap[E->getRHS()] = RHSCount;
     Visit(E->getRHS());
-    setCount(ParentCount + RHSCount - PGO.getCurrentRegionCount());
+    setCount(ParentCount + RHSCount - CurrentCount);
     RecordNextStmtCount = true;
   }
 };
diff --git a/clang/lib/CodeGen/CodeGenPGO.h b/clang/lib/CodeGen/CodeGenPGO.h
index d73d030e7b0..13bb5a2fc86 100644
--- a/clang/lib/CodeGen/CodeGenPGO.h
+++ b/clang/lib/CodeGen/CodeGenPGO.h
@@ -60,11 +60,6 @@ public:
   /// exits.
   void setCurrentRegionCount(uint64_t Count) { CurrentRegionCount = Count; }
 
-  /// Indicate that the current region is never reached, and thus should have a
-  /// counter value of zero. This is important so that subsequent regions can
-  /// correctly track their parent counts.
-  void setCurrentRegionUnreachable() { setCurrentRegionCount(0); }
-
   /// Check if an execution count is known for a given statement. If so, return
   /// true and put the value in Count; else return false.
   Optional<uint64_t> getStmtCount(const Stmt *S) {