[ownership] Ignore non-consuming uses in dead end blocks when we are analyzing objects that are consumed once in the same block in which they are defined.

Author: gottesmm

lib/SIL/LinearLifetimeChecker.cpp

@@ -486,11 +486,12 @@ LinearLifetimeError swift::valueHasLinearLifetime(
   // have been detected by initializing our consuming uses. So we are done.
   if (consumingUses.size() == 1 &&
       consumingUses[0].getParent() == value->getParentBlock()) {
-    // Check if any of our non consuming uses are not in the parent block. We
-    // flag those as additional use after frees. Any in the same block, we would
-    // have flagged.
+    // Check if any of our non consuming uses are not in the parent block and
+    // are reachable. We flag those as additional use after frees. Any in the
+    // same block, we would have flagged.
     if (llvm::any_of(nonConsumingUses, [&](BranchPropagatedUser user) {
-          return user.getParent() != value->getParentBlock();
+          return user.getParent() != value->getParentBlock() &&
+            !deBlocks.isDeadEnd(user.getParent());
         })) {
       state.error.handleUseAfterFree([&] {
         llvm::errs() << "Function: '" << value->getFunction()->getName()

test/SIL/ownership-verifier/use_verifier.sil

@@ -105,6 +105,10 @@ sil @unowned_tuple_user : $@convention(thin) ((Builtin.Int32, Builtin.NativeObje
 sil @produce_owned_optional : $@convention(thin) () -> @owned Optional<Builtin.NativeObject>
 sil @guaranteed_nativeobject_user : $@convention(thin) (@guaranteed Builtin.NativeObject) -> ()
 
+class UnsafeUnownedFieldKlass {
+  unowned(safe) var x: @sil_unowned Builtin.NativeObject
+}
+
 ////////////////
 // Test Cases //
 ////////////////
@@ -1156,3 +1160,26 @@ bb0:
   %9999 = tuple()
   return %9999 : $()
 }
+
+// Make sure that we do not false positive due to borrow users of %12 in an
+// unreachable block.
+sil [ossa] @test_unreachable_users : $@convention(method) (@guaranteed UnsafeUnownedFieldKlass) -> () {
+bb0(%0 : @guaranteed $UnsafeUnownedFieldKlass):
+  %3 = ref_element_addr %0 : $UnsafeUnownedFieldKlass, #UnsafeUnownedFieldKlass.x
+  %4 = load_borrow %3 : $*@sil_unowned Builtin.NativeObject
+  %5 = copy_unowned_value %4 : $@sil_unowned Builtin.NativeObject
+  end_borrow %4 : $@sil_unowned Builtin.NativeObject
+  %12 = begin_borrow %5 : $Builtin.NativeObject
+  %func = function_ref @guaranteed_nativeobject_user : $@convention(thin) (@guaranteed Builtin.NativeObject) -> ()
+  apply %func(%12) : $@convention(thin) (@guaranteed Builtin.NativeObject) -> ()
+  end_borrow %12 : $Builtin.NativeObject
+  destroy_value %5 : $Builtin.NativeObject
+  %36 = tuple ()
+  return %36 : $()
+
+bb1:
+  %func2 = function_ref @guaranteed_nativeobject_user : $@convention(thin) (@guaranteed Builtin.NativeObject) -> ()
+  apply %func2(%12) : $@convention(thin) (@guaranteed Builtin.NativeObject) -> ()
+  unreachable
+}
+