[6.0] Fix SILCombine of inject_enum_addr to correctly check for unreferenceable storage

include/swift/SILOptimizer/Utils/InstOptUtils.h

@@ -604,6 +604,10 @@ bool specializeAppliesInFunction(SILFunction &F,
 /// types aggregated together at each level.
 SILValue createEmptyAndUndefValue(SILType ty, SILInstruction *insertionPoint,
                                   SILBuilderContext &ctx, bool noUndef = false);
+
+/// Check if a struct or its fields can have unreferenceable storage.
+bool findUnreferenceableStorage(StructDecl *decl, SILType structType,
+                                SILFunction *func);
 } // end namespace swift
 
 #endif // SWIFT_SILOPTIMIZER_UTILS_INSTOPTUTILS_H

lib/SILOptimizer/SILCombiner/SILCombinerMiscVisitors.cpp

@@ -1246,7 +1246,7 @@ SILCombiner::visitInjectEnumAddrInst(InjectEnumAddrInst *IEAI) {
 
   // We cannot create a struct when it has unreferenceable storage.
   if (elemType.isEmpty(*IEAI->getFunction()) && structDecl &&
-      structDecl->hasUnreferenceableStorage()) {
+      findUnreferenceableStorage(structDecl, elemType, IEAI->getFunction())) {
     return nullptr;
   }
 

lib/SILOptimizer/Utils/InstOptUtils.cpp

@@ -2009,3 +2009,21 @@ SILValue swift::createEmptyAndUndefValue(SILType ty,
   assert(!noUndef);
   return SILUndef::get(insertionPoint->getFunction(), ty);
 }
+
+bool swift::findUnreferenceableStorage(StructDecl *decl, SILType structType,
+                                       SILFunction *func) {
+  if (decl->hasUnreferenceableStorage()) {
+    return true;
+  }
+  // Check if any fields have unreferenceable stoage
+  for (auto *field : decl->getStoredProperties()) {
+    TypeExpansionContext tec = *func;
+    auto fieldTy = structType.getFieldType(field, func->getModule(), tec);
+    if (auto *fieldStructDecl = fieldTy.getStructOrBoundGenericStruct()) {
+      if (findUnreferenceableStorage(fieldStructDecl, fieldTy, func)) {
+        return true;
+      }
+    }
+  }
+  return false;
+}

test/SILOptimizer/sil_combine_enum_addr.sil

@@ -362,3 +362,33 @@ bb3:
   %8 = tuple ()
   return %8 : $()
 }
+
+struct NestedUnreferenceableStorage {
+  let e: EmptyCUnion
+}
+
+sil @no_init_nested_c_union : $@convention(thin) () -> (@out NestedUnreferenceableStorage)
+
+// CHECK-LABEL: sil @test_empty_nested_c_union : $@convention(thin) () -> () {
+// CHECK: inject_enum_addr
+// CHECK-LABEL: } // end sil function 'test_empty_nested_c_union'
+sil @test_empty_nested_c_union : $@convention(thin) () -> () {
+bb0:
+  %0 = alloc_stack $Optional<NestedUnreferenceableStorage>
+  %1 = init_enum_data_addr %0 : $*Optional<NestedUnreferenceableStorage>, #Optional.some!enumelt
+  %f = function_ref @no_init_nested_c_union : $@convention(thin) () -> (@out NestedUnreferenceableStorage)
+  apply %f(%1) : $@convention(thin) () -> (@out NestedUnreferenceableStorage)
+  inject_enum_addr %0 : $*Optional<NestedUnreferenceableStorage>, #Optional.some!enumelt
+  switch_enum_addr %0 : $*Optional<NestedUnreferenceableStorage>, case #Optional.some!enumelt: bb1, case #Optional.none!enumelt: bb2
+
+bb1:
+  br bb3
+
+bb2:
+  br bb3
+
+bb3:
+  dealloc_stack %0 : $*Optional<NestedUnreferenceableStorage>
+  %8 = tuple ()
+  return %8 : $()
+}