[ShrinkBorrowScope] Used extract deinit barrier implementation.

In 0325e29, the implementation of
deinit barrier predicate was copied out of ShrinkBorrowScope into
MemAccessUtils.  Delete the source of that copy from ShrinkBorrowScope
and just call the now common utility.

Author: nate-chandler

lib/SILOptimizer/Utils/ShrinkBorrowScope.cpp

@@ -88,35 +88,6 @@ class ShrinkBorrowScope {
   bool rewrite();
   bool createEndBorrow(SILInstruction *insertionPoint);
 
-  bool isBarrierApply(SILInstruction *instruction) {
-    // For now, treat every apply (that doesn't use the borrowed value) as a
-    // barrier.
-    return isa<ApplySite>(instruction);
-  }
-
-  bool mayAccessPointer(SILInstruction *instruction) {
-    if (!instruction->mayReadOrWriteMemory())
-      return false;
-    bool fail = false;
-    visitAccessedAddress(instruction, [&fail](Operand *operand) {
-      auto accessStorage = AccessStorage::compute(operand->get());
-      if (accessStorage.getKind() != AccessRepresentation::Kind::Unidentified)
-        fail = true;
-    });
-    return fail;
-  }
-
-  bool mayLoadWeakOrUnowned(SILInstruction *instruction) {
-    // TODO: It is possible to do better here by looking at the address that is
-    //       being loaded.
-    return isa<LoadWeakInst>(instruction) || isa<LoadUnownedInst>(instruction);
-  }
-
-  bool isDeinitBarrier(SILInstruction *instruction) {
-    return isBarrierApply(instruction) || instruction->maySynchronize() ||
-           mayAccessPointer(instruction) || mayLoadWeakOrUnowned(instruction);
-  }
-
   bool canReplaceValueWithBorrowee(SILValue value) {
     while (true) {
       auto *instruction = value.getDefiningInstruction();