Look through forwarding instructions while querying ownership root

Fixes rdar://142507746

Author: meg-gupta

include/swift/SIL/MemAccessUtils.h

@@ -638,6 +638,13 @@ class AccessBase : public AccessRepresentation {
     return findOwnershipReferenceRoot(getReference());
   }
 
+  /// Return the OSSA root of the reference being accessed
+  /// looking through struct_extract, tuple_extract, etc.
+  /// Precondition: isReference() is true.
+  SILValue getOwnershipReferenceAggregate() const {
+    return findOwnershipReferenceAggregate(getReference());
+  }
+  
   /// Return the storage root of the reference being accessed.
   ///
   /// Precondition: isReference() is true.

lib/SIL/Utils/OwnershipUtils.cpp

@@ -1092,7 +1092,7 @@ bool AddressOwnership::areUsesWithinLifetime(
   if (!base.hasLocalOwnershipLifetime())
     return true;
 
-  SILValue root = base.getOwnershipReferenceRoot();
+  SILValue root = base.getOwnershipReferenceAggregate();
   BorrowedValue borrow(root);
   if (borrow)
     return borrow.areUsesWithinExtendedScope(uses, &deadEndBlocks);

test/SILOptimizer/cse_ossa_nontrivial.sil

@@ -1010,3 +1010,26 @@ bb0:
  return %t : $()
 }
 
+// CHECK-LABEL: sil [ossa] @test_aggreate_tail_addr :
+// CHECK: ref_tail_addr
+// CHECK: ref_tail_addr
+// CHECK-LABEL: } // end sil function 'test_aggreate_tail_addr'
+sil [ossa] @test_aggreate_tail_addr : $@convention(thin) (@owned _NativeDictionary<Int, Klass>) -> () {
+bb0(%0 : @owned $_NativeDictionary<Int, Klass>):
+  %49 = move_value [lexical] %0 : $_NativeDictionary<Int, Klass> 
+  %50 = begin_borrow %49
+  %51 = struct_extract %50, #_NativeDictionary._storage
+  %52 = copy_value %51
+  %53 = ref_tail_addr %51, $_UnsafeBitset.Word
+  %59 = load [trivial] %53
+  end_borrow %50
+  %72 = begin_borrow %52
+  %73 = ref_tail_addr %72, $_UnsafeBitset.Word
+  %74 = struct_element_addr %73, #_UnsafeBitset.Word.value
+  %75 = struct_element_addr %74, #UInt._value
+  %76 = load [trivial] %75
+  end_borrow %72
+  destroy_value %52
+  destroy_value %49
+  unreachable
+}