[sil-optimizer] Remove the opened archetypes related workarounds which are obsolete now.

Now we properly track the dependencies between instructions using opened archetypes and instructions opening those archetypes. No need for any special handling anymore.

Author: swiftix

lib/SILOptimizer/LoopTransforms/LICM.cpp

@@ -231,13 +231,6 @@ static bool canHoistInstruction(SILInstruction *Inst, SILLoop *Loop,
   if (isa<AllocationInst>(Inst) || isa<DeallocStackInst>(Inst))
     return false;
 
-  // Can't hoist metatype instruction referring to an opened existential,
-  // because it may break the dominance relationship.
-  if (isa<MetatypeInst>(Inst) &&
-      Inst->getType().getSwiftRValueType()->hasOpenedExistential()) {
-    return false;
-  }
-
   // Can't hoist instructions which may have side effects.
   if (!hasNoSideEffect(Inst, SafeReads))
     return false;

lib/SILOptimizer/Transforms/Sink.cpp

@@ -67,19 +67,6 @@ class CodeSinkingPass : public SILFunctionTransform {
     if (II->isAllocatingStack() || II->isDeallocatingStack())
       return false;
 
-    // We don't sink open_existential_* instructions, because
-    // there may be some instructions depending on them, e.g.
-    // metatype_inst, etc. But this kind of dependency
-    // cannot be expressed in SIL yet.
-    switch (II->getKind()) {
-    default: break;
-    case ValueKind::OpenExistentialBoxInst:
-    case ValueKind::OpenExistentialRefInst:
-    case ValueKind::OpenExistentialAddrInst:
-    case ValueKind::OpenExistentialMetatypeInst:
-      return false;
-    }
-
     SILBasicBlock *CurrentBlock = II->getParent();
     SILBasicBlock *Dest = nullptr;
     unsigned InitialLoopDepth = LoopInfo->getLoopDepth(CurrentBlock);