Merge pull request #84946 from eeckstein/fix-simplify-cfg-6.2

[6.2] SimplifyCFG: insert compensating destroy when replacing a `switch_enum`

Author: eeckstein

lib/SILOptimizer/Transforms/SimplifyCFG.cpp

@@ -1791,7 +1791,12 @@ bool SimplifyCFG::simplifySwitchEnumUnreachableBlocks(SwitchEnumInst *SEI) {
   }
 
   if (Dest->args_empty()) {
-    SILBuilderWithScope(SEI).createBranch(SEI->getLoc(), Dest);
+    SILBuilderWithScope builder(SEI);
+    if (SEI->getOperand()->getOwnershipKind() == OwnershipKind::Owned) {
+      // Note that a `destroy_value` would be wrong for non-copyable enums with deinits.
+      builder.createEndLifetime(SEI->getLoc(), SEI->getOperand());
+    }
+    builder.createBranch(SEI->getLoc(), Dest);
 
     addToWorklist(SEI->getParent());
     addToWorklist(Dest);

test/SILOptimizer/simplify_cfg_ossa.sil

@@ -1,4 +1,6 @@
-// RUN: %target-sil-opt -sil-print-types -enable-objc-interop -enable-sil-verify-all %s -simplify-cfg | %FileCheck %s
+// RUN: %target-sil-opt -sil-print-types -enable-objc-interop -enable-experimental-feature MoveOnlyEnumDeinits -enable-sil-verify-all %s -simplify-cfg | %FileCheck %s
+
+// REQUIRES: swift_feature_MoveOnlyEnumDeinits
 
 // OSSA form of tests from simplify_cfg.sil and simplify_cfg_simple.sil.
 //
@@ -64,6 +66,12 @@ struct S {
   var b: NonTrivial
 }
 
+enum NCE: ~Copyable {
+  case a
+  case b(AnyObject)
+  deinit
+}
+
 ///////////
 // Tests //
 ///////////
@@ -1944,6 +1952,44 @@ bb3:
   return %t : $()
 }
 
+// CHECK-LABEL: sil [ossa] @insert_compensating_endlifetime_in_switch_enum_destination_block :
+// CHECK:       bb0(%0 : @owned $Optional<AnyObject>):
+// CHECK-NEXT:    end_lifetime %0
+// CHECK-NEXT:    tuple
+// CHECK:       } // end sil function 'insert_compensating_endlifetime_in_switch_enum_destination_block'
+sil [ossa] @insert_compensating_endlifetime_in_switch_enum_destination_block : $@convention(thin) (@owned Optional<AnyObject>) -> () {
+bb0(%0 : @owned $Optional<AnyObject>):
+  switch_enum %0, case #Optional.none!enumelt: bb1, case #Optional.some!enumelt: bb2
+
+bb1:
+  %15 = tuple ()
+  return %15
+
+bb2(%4 : @owned $AnyObject):
+  destroy_value %4
+  unreachable
+}
+
+// CHECK-LABEL: sil [ossa] @insert_compensating_endlifetime_in_switch_enum_destination_block2 :
+// CHECK:       bb0(%0 : @owned $NCE):
+// CHECK-NEXT:    %1 = drop_deinit %0
+// CHECK-NEXT:    end_lifetime %1
+// CHECK-NEXT:    tuple
+// CHECK:       } // end sil function 'insert_compensating_endlifetime_in_switch_enum_destination_block2'
+sil [ossa] @insert_compensating_endlifetime_in_switch_enum_destination_block2 : $@convention(thin) (@owned NCE) -> () {
+bb0(%0 : @owned $NCE):
+  %1 = drop_deinit %0
+  switch_enum %1, case #NCE.a!enumelt: bb1, case #NCE.b!enumelt: bb2
+
+bb1:
+  %15 = tuple ()
+  return %15
+
+bb2(%4 : @owned $AnyObject):
+  destroy_value %4
+  unreachable
+}
+
 // CHECK-LABEL: sil [ossa] @replace_phi_arg_with_borrowed_from_use :
 // CHECK:       bb3([[R:%.*]] : @reborrow $B):
 // CHECK:       bb6([[G:%.*]] : @guaranteed $E):