Revert "[arc] Put back in the RCIdentity cache."

This reverts commit 6c728da.

This is a speculative revert to try and fix the ASAN build.

Author: gottesmm

include/swift/SILOptimizer/Analysis/RCIdentityAnalysis.h

@@ -32,7 +32,6 @@ class DominanceAnalysis;
 /// This class is a simple wrapper around an identity cache.
 class RCIdentityFunctionInfo {
   llvm::DenseSet<SILArgument *> VisitedArgs;
-  llvm::DenseMap<SILValue, SILValue> Cache;
   DominanceAnalysis *DA;
 
   /// This number is arbitrary and conservative. At some point if compile time
@@ -51,16 +50,6 @@ class RCIdentityFunctionInfo {
   /// unchecked_trivial_bit_cast.
   void getRCUsers(SILValue V, llvm::SmallVectorImpl<SILInstruction *> &Users);
 
-  void handleDeleteNotification(SILInstruction *I) {
-    // Check the cache. If we don't find it, there is nothing to do.
-    auto Iter = Cache.find(SILValue(I));
-    if (Iter == Cache.end())
-      return;
-
-    // Then erase Iter from the cache.
-    Cache.erase(Iter);
-  }
-
 private:
   SILValue getRCIdentityRootInner(SILValue V, unsigned RecursionDepth);
   SILValue stripRCIdentityPreservingOps(SILValue V, unsigned RecursionDepth);
@@ -95,23 +84,6 @@ class RCIdentityAnalysis : public FunctionAnalysisBase<RCIdentityFunctionInfo> {
     return true;
   }
 
-  virtual void handleDeleteNotification(ValueBase *V) override {
-    auto *I = dyn_cast<SILInstruction>(V);
-    // We are only interesting in SILInstructions.
-    if (!I || !I->getParentBB())
-      return;
-
-    // If the parent function of this instruction was just turned into an
-    // external declaration, bail. This happens during SILFunction destruction,
-    // when
-    SILFunction *F = I->getFunction();
-    if (F->isExternalDeclaration()) {
-      return;
-    }
-    get(F)->handleDeleteNotification(I);
-  }
-
-  virtual bool needsNotifications() override { return true; }
  };
 
 } // end swift namespace

lib/SILOptimizer/Analysis/RCIdentityAnalysis.cpp

@@ -54,12 +54,6 @@ static bool isRCIdentityPreservingCast(ValueKind Kind) {
 //                    RC Identity Root Instruction Casting
 //===----------------------------------------------------------------------===//
 
-static SILValue stripRCIdentityPreservingCasts(SILValue V) {
-  while (isRCIdentityPreservingCast(V->getKind()))
-    V = cast<SILInstruction>(V)->getOperand(0);
-  return V;
-}
-
 static SILValue stripRCIdentityPreservingInsts(SILValue V) {
   // First strip off RC identity preserving casts.
   if (isRCIdentityPreservingCast(V->getKind()))
@@ -451,30 +445,14 @@ SILValue RCIdentityFunctionInfo::getRCIdentityRootInner(SILValue V,
 }
 
 SILValue RCIdentityFunctionInfo::getRCIdentityRoot(SILValue V) {
-  // We save some memory here by stripping off casts from any V. This is good to
-  // do since stripping off casts is the cheap part of
-  // stripRCIdentityPreservingInsts and reduces the number of possible values we
-  // can track.
-  //
-  // The expensive parts of stripRCIdentityPreservingInsts function are the
-  // unique non trivial elt calls. It should be investigated if they fit well
-  // here as well.
-  SILValue NoCastV = stripRCIdentityPreservingCasts(V);
-  auto Iter = Cache.find(NoCastV);
-  if (Iter != Cache.end())
-    return Iter->second;
-
-  SILValue Root = getRCIdentityRootInner(NoCastV, 0);
+  SILValue Root = getRCIdentityRootInner(V, 0);
   VisitedArgs.clear();
 
-  // If we fail to find a root, return NoCastV.
-  //
-  // We know that stripping off RC identical preserving casts is always safe, so
-  // since NoCastV is "better" information, we can return it without issue.
+  // If we fail to find a root, return V.
   if (!Root)
-    return NoCastV;
+    return V;
 
-  return Cache[NoCastV] = Root;
+  return Root;
 }
 
 //===----------------------------------------------------------------------===//