Remove all comments related to 'insertion points' in ARCSequenceOpts

Historically ARC code motion was also part of ARCSequenceOpts. Remove
some stale comments regarding 'insertion points'

Author: meg-gupta

lib/SILOptimizer/ARC/ARCMatchingSet.cpp

@@ -68,8 +68,6 @@ ARCMatchingSetBuilder::matchIncrementsToDecrements() {
       continue;
     }
 
-    // We need to be known safe over all increments/decrements we are matching
-    // up to ignore insertion points.
     bool BUIsKnownSafe = (*BURefCountState)->second.isKnownSafe();
     LLVM_DEBUG(llvm::dbgs() << "        BOTTOM UP KNOWNSAFE: "
                             << (BUIsKnownSafe ? "true" : "false") << "\n");
@@ -152,8 +150,6 @@ ARCMatchingSetBuilder::matchDecrementsToIncrements() {
       continue;
     }
 
-    // We need to be known safe over all increments/decrements we are matching
-    // up to ignore insertion points.
     bool TDIsKnownSafe = (*TDRefCountState)->second.isKnownSafe();
     LLVM_DEBUG(llvm::dbgs() << "        TOP DOWN KNOWNSAFE: "
                             << (TDIsKnownSafe ? "true" : "false") << "\n");
@@ -223,7 +219,7 @@ bool ARCMatchingSetBuilder::matchUpIncDecSetsForPtr() {
     LLVM_DEBUG(llvm::dbgs() << "Attempting to match up increments -> "
                "decrements:\n");
     // For each increment in our list of new increments, attempt to match them
-    // up with decrements and gather the insertion points of the decrements.
+    // up with decrements.
     auto Result = matchIncrementsToDecrements();
     if (!Result) {
       LLVM_DEBUG(llvm::dbgs() << "    FAILED TO MATCH INCREMENTS -> "
@@ -287,8 +283,6 @@ bool ARCMatchingSetBuilder::matchUpIncDecSetsForPtr() {
   assert(MatchSet.Increments.empty() == MatchSet.Decrements.empty() &&
          "Match set without increments or decrements");
 
-  // If we do not have any insertion points but we do have increments, we must
-  // be eliminating pairs.
   if (!MatchSet.Increments.empty())
     MatchedPair = true;
 

lib/SILOptimizer/ARC/ARCRegionState.cpp

@@ -188,7 +188,7 @@ static bool isARCSignificantTerminator(TermInst *TI) {
 
 // Visit each one of our predecessor regions and see if any are blocks that can
 // use reference counted values. If any of them do, we advance the sequence for
-// the pointer and create an insertion point here. This state will be propagated
+// the pointer. This state will be propagated
 // into all of our predecessors, allowing us to be conservatively correct in all
 // cases.
 //
@@ -305,9 +305,8 @@ bool ARCRegionState::processBlockBottomUp(
 
   // Now visit each one of our predecessor regions and see if any are blocks
   // that can use reference counted values. If any of them do, we advance the
-  // sequence for the pointer and create an insertion point here. This state
-  // will be propagated into all of our predecessors, allowing us to be
-  // conservatively correct in all cases.
+  // sequence for the pointer. This state will be propagated into all of our
+  // predecessors, allowing us to be conservatively correct in all cases.
   processBlockBottomUpPredTerminators(R, AA, LRFI, SetFactory);
 
   return NestingDetected;

lib/SILOptimizer/ARC/ARCSequenceOpts.cpp

@@ -45,10 +45,8 @@ llvm::cl::opt<bool> EnableLoopARC("enable-loop-arc", llvm::cl::init(false));
 //                                Code Motion
 //===----------------------------------------------------------------------===//
 
-// This routine takes in the ARCMatchingSet \p MatchSet and inserts new
-// increments, decrements at the insertion points and adds the old increment,
-// decrements to the delete list. Sets changed to true if anything was moved or
-// deleted.
+// This routine takes in the ARCMatchingSet \p MatchSet and adds the increments
+// and decrements to the delete list.
 void ARCPairingContext::optimizeMatchingSet(
     ARCMatchingSet &MatchSet, llvm::SmallVectorImpl<SILInstruction *> &NewInsts,
     llvm::SmallVectorImpl<SILInstruction *> &DeadInsts) {
@@ -99,9 +97,6 @@ bool ARCPairingContext::performMatching(
       for (auto *I : Set.Decrements)
         DecToIncStateMap.erase(I);
 
-      // Add the Set to the callback. *NOTE* No instruction destruction can
-      // happen here since we may remove instructions that are insertion points
-      // for other instructions.
       optimizeMatchingSet(Set, NewInsts, DeadInsts);
     }
   }

lib/SILOptimizer/ARC/RefCountState.cpp

@@ -241,14 +241,11 @@ bool BottomUpRefCountState::handleGuaranteedUser(
 
   // Advance the sequence...
   switch (LatState) {
-  // If were decremented, insert the insertion point.
   case LatticeState::Decremented: {
     LatState = LatticeState::MightBeDecremented;
     return true;
   }
   case LatticeState::MightBeUsed:
-    // If we have a might be used, we already created an insertion point
-    // earlier. Just move to MightBeDecremented.
     LatState = LatticeState::MightBeDecremented;
     return true;
   case LatticeState::MightBeDecremented:
@@ -705,14 +702,11 @@ bool TopDownRefCountState::handleGuaranteedUser(
          "Must be able to be used at this point of the lattice.");
   // Advance the sequence...
   switch (LatState) {
-  // If were decremented, insert the insertion point.
   case LatticeState::Incremented: {
     LatState = LatticeState::MightBeUsed;
     return true;
   }
   case LatticeState::MightBeDecremented:
-    // If we have a might be used, we already created an insertion point
-    // earlier. Just move to MightBeDecremented.
     LatState = LatticeState::MightBeUsed;
     return true;
   case LatticeState::MightBeUsed: