CopyToBorrowOptimization: correctly handle unchecked_enum_data

A `unchecked_enum_data` which extracts a trivial payload out of a non-trivial enum ends the lifetime of its owned operand.

Fixes an ownership verification error
rdar://142644731

Author: eeckstein

SwiftCompilerSources/Sources/Optimizer/FunctionPasses/CopyToBorrowOptimization.swift

@@ -185,6 +185,11 @@ private struct Uses {
       for succ in termInst.successors where !succ.arguments.contains(where: {$0.ownership == .owned}) {
         nonDestroyingLiverangeExits.append(succ.instructions.first!)
       }
+    } else if !forwardingInst.forwardedResults.contains(where: { $0.ownership == .owned }) {
+      // The forwarding instruction has no owned result, which means it ends the lifetime of its owned operand.
+      // This can happen with an `unchecked_enum_data` which extracts a trivial payload out of a
+      // non-trivial enum.
+      nonDestroyingLiverangeExits.append(forwardingInst.next!)
     }
   }
 

test/SILOptimizer/copy-to-borrow-optimization.sil

@@ -2146,3 +2146,16 @@ bb3:
   %r = tuple ()
   return %r
 }
+
+// CHECK-LABEL: sil [ossa] @lifetime_ending_enum_data :
+// CHECK:         %1 = load_borrow %0
+// CHECK-NEXT:    %2 = unchecked_enum_data %1
+// CHECK-NEXT:    end_borrow %1
+// CHECK:       } // end sil function 'lifetime_ending_enum_data'
+sil [ossa] @lifetime_ending_enum_data : $@convention(method) (@in_guaranteed MultiPayload) -> MyInt {
+bb0(%0 : $*MultiPayload):
+  %1 = load [copy] %0
+  %2 = unchecked_enum_data %1, #MultiPayload.b!enumelt
+  return %2
+}
+