Revert "[AliasSetTracker] Make AST smarter about intrinsics that don't actually affect memory."

This reverts commit r285191.

LICM appears to rely on the Alias Set Tracker hitting lifetime markers to prevent
code from being moved outside of the original scope.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@285227 91177308-0d34-0410-b5e6-96231b3b80d8

Author: mcrosier

lib/Analysis/AliasSetTracker.cpp

@@ -413,21 +413,6 @@ void AliasSetTracker::add(MemTransferInst *MTI) {
 void AliasSetTracker::addUnknown(Instruction *Inst) {
   if (isa<DbgInfoIntrinsic>(Inst))
     return; // Ignore DbgInfo Intrinsics.
-
-  if (auto *II = dyn_cast<IntrinsicInst>(Inst)) {
-    // These intrinsics will show up as affecting memory, but they are just
-    // markers.
-    switch (II->getIntrinsicID()) {
-    default:
-      break;
-    case Intrinsic::lifetime_start:
-    case Intrinsic::lifetime_end:
-    case Intrinsic::invariant_start:
-    case Intrinsic::invariant_end:
-    case Intrinsic::assume:
-      return;
-    }
-  }
   if (!Inst->mayReadOrWriteMemory())
     return; // doesn't alias anything