[NewGVN] Slightly clean up the predicate swap handling (NFC)

I found the naming here confusing. This is not something generic
for intrinsics, it's specifically about predicates, and serves to
remember a previous swap choice.

Author: nikic

llvm/lib/Transforms/Scalar/NewGVN.cpp

@@ -651,7 +651,7 @@ class NewGVN {
   BitVector TouchedInstructions;
 
   DenseMap<const BasicBlock *, std::pair<unsigned, unsigned>> BlockInstRange;
-  mutable DenseMap<const IntrinsicInst *, const Value *> IntrinsicInstPred;
+  mutable DenseMap<const IntrinsicInst *, const Value *> PredicateSwapChoice;
 
 #ifndef NDEBUG
   // Debugging for how many times each block and instruction got processed.
@@ -840,7 +840,7 @@ class NewGVN {
   // Ranking
   unsigned int getRank(const Value *) const;
   bool shouldSwapOperands(const Value *, const Value *) const;
-  bool shouldSwapOperandsForIntrinsic(const Value *, const Value *,
+  bool shouldSwapOperandsForPredicate(const Value *, const Value *,
                                       const IntrinsicInst *I) const;
 
   // Reachability handling.
@@ -1624,7 +1624,7 @@ NewGVN::performSymbolicPredicateInfoEvaluation(IntrinsicInst *I) const {
   Value *AdditionallyUsedValue = CmpOp0;
 
   // Sort the ops.
-  if (shouldSwapOperandsForIntrinsic(FirstOp, SecondOp, I)) {
+  if (shouldSwapOperandsForPredicate(FirstOp, SecondOp, I)) {
     std::swap(FirstOp, SecondOp);
     Predicate = CmpInst::getSwappedPredicate(Predicate);
     AdditionallyUsedValue = CmpOp1;
@@ -3024,7 +3024,7 @@ void NewGVN::cleanupTables() {
   PredicateToUsers.clear();
   MemoryToUsers.clear();
   RevisitOnReachabilityChange.clear();
-  IntrinsicInstPred.clear();
+  PredicateSwapChoice.clear();
 }
 
 // Assign local DFS number mapping to instructions, and leave space for Value
@@ -4250,20 +4250,18 @@ bool NewGVN::shouldSwapOperands(const Value *A, const Value *B) const {
   return std::make_pair(getRank(A), A) > std::make_pair(getRank(B), B);
 }
 
-bool NewGVN::shouldSwapOperandsForIntrinsic(const Value *A, const Value *B,
+bool NewGVN::shouldSwapOperandsForPredicate(const Value *A, const Value *B,
                                             const IntrinsicInst *I) const {
-  auto LookupResult = IntrinsicInstPred.find(I);
   if (shouldSwapOperands(A, B)) {
-    if (LookupResult == IntrinsicInstPred.end())
-      IntrinsicInstPred.insert({I, B});
-    else
-      LookupResult->second = B;
+    PredicateSwapChoice[I] = B;
     return true;
   }
 
-  if (LookupResult != IntrinsicInstPred.end()) {
+  auto LookupResult = PredicateSwapChoice.find(I);
+  if (LookupResult != PredicateSwapChoice.end()) {
     auto *SeenPredicate = LookupResult->second;
     if (SeenPredicate) {
+      // We previously decided to swap B to the left. Keep that choice.
       if (SeenPredicate == B)
         return true;
       else