[SCEV][NFC] Win some compile time from mass forgetMemoizedResults

[mkazantsev]

Summary

Mass forgetMemoizedResults can be done more efficiently than bunch
of individual invocations of helper because we can traverse maps being
updated just once, rather than doing this for each invidivual SCEV.

Should be NFC and supposedly improves compile time.

[reames]

LGTM

llvm/lib/Analysis/ScalarEvolution.cpp

12786

Personally, I'd inline this into the single caller as having it out of line doesn't seem to add any value, but I don't hugely care either way.

llvm/lib/Analysis/ScalarEvolution.cpp

 
 bool ScalarEvolution::hasOperand(const SCEV *S, const SCEV *Op) const {
   return SCEVExprContains(S, [&](const SCEV *Expr) { return Expr == Op; });
 }
 
 void ScalarEvolution::forgetMemoizedResults(ArrayRef<const SCEV *> SCEVs) {
   for (auto *S : SCEVs)
     forgetMemoizedResultsImpl(S);
-}
-
-void ScalarEvolution::forgetMemoizedResultsImpl(const SCEV *S) {
-  ValuesAtScopes.erase(S);
-  LoopDispositions.erase(S);
-  BlockDispositions.erase(S);
-  UnsignedRanges.erase(S);
-  SignedRanges.erase(S);
-  ExprValueMap.erase(S);
-  HasRecMap.erase(S);
-  MinTrailingZerosCache.erase(S);
-
+  SmallPtrSet<const SCEV *, 8> ToForget(SCEVs.begin(), SCEVs.end());
   for (auto I = PredicatedSCEVRewrites.begin();
        I != PredicatedSCEVRewrites.end();) {
     std::pair<const SCEV *, const Loop *> Entry = I->first;
-    if (Entry.first == S)
+    if (ToForget.count(Entry.first))
       PredicatedSCEVRewrites.erase(I++);
     else
       ++I;
   }
 
-  auto RemoveSCEVFromBackedgeMap =
-      [S](DenseMap<const Loop *, BackedgeTakenInfo> &Map) {
+  auto RemoveSCEVFromBackedgeMap = [this, &ToForget](
+      DenseMap<const Loop *, BackedgeTakenInfo> &Map) {
         for (auto I = Map.begin(), E = Map.end(); I != E;) {
           BackedgeTakenInfo &BEInfo = I->second;
-          if (BEInfo.hasOperand(S))
+          if (any_of(ToForget,
+                     [&BEInfo](const SCEV *S) { return BEInfo.hasOperand(S); }))
             Map.erase(I++);
           else
             ++I;
         }
-      };
 
   RemoveSCEVFromBackedgeMap(BackedgeTakenCounts);
   RemoveSCEVFromBackedgeMap(PredicatedBackedgeTakenCounts);
 }
 
+void ScalarEvolution::forgetMemoizedResultsImpl(const SCEV *S) {
+  ValuesAtScopes.erase(S);
+  LoopDispositions.erase(S);
+  BlockDispositions.erase(S);
+  UnsignedRanges.erase(S);
+  SignedRanges.erase(S);
+  ExprValueMap.erase(S);
+  HasRecMap.erase(S);
+  MinTrailingZerosCache.erase(S);
+}
+
 void
 ScalarEvolution::getUsedLoops(const SCEV *S,
                               SmallPtrSetImpl<const Loop *> &LoopsUsed) {
   struct FindUsedLoops {
     FindUsedLoops(SmallPtrSetImpl<const Loop *> &LoopsUsed)
         : LoopsUsed(LoopsUsed) {}
     SmallPtrSetImpl<const Loop *> &LoopsUsed;
     bool follow(const SCEV *S) {