[Runtime] Fix missing memcpy in handleSingleRefCountInitWithCopy

rdar://117755666

Missing memcpy in handleSingleRefCountInitWithCopy caused wrong enum cases, crashes etc.

Author: drexin

stdlib/public/runtime/BytecodeLayouts.cpp

@@ -281,7 +281,7 @@ static void singlePayloadEnumGeneric(const Metadata *metadata,
     if (SWIFT_LIKELY(xiType)) {
       auto tag = xiType->vw_getEnumTagSinglePayload(
           (const OpaqueValue *)(addr + addrOffset + xiTagBytesOffset),
-          numEmptyCases);
+          xiType->vw_getNumExtraInhabitants());
       if (SWIFT_LIKELY(tag == 0)) {
         return;
       }
@@ -501,7 +501,7 @@ static void singlePayloadEnumGeneric(const Metadata *metadata,
     if (SWIFT_LIKELY(xiType)) {
       auto tag = xiType->vw_getEnumTagSinglePayload(
           (const OpaqueValue *)(src + addrOffset + xiTagBytesOffset),
-          numEmptyCases);
+          xiType->vw_getNumExtraInhabitants());
       if (SWIFT_LIKELY(tag == 0)) {
         return;
       }
@@ -1317,7 +1317,12 @@ static void handleSingleRefCountInitWithCopy(const Metadata *metadata,
                                         uint8_t *dest,
                                         uint8_t *src) {
   auto tag = reader.readBytes<uint64_t>();
-  addrOffset += (tag & ~(0xFFULL << 56));
+  auto _addrOffset = addrOffset;
+  auto offset = (tag & ~(0xFFULL << 56));
+  if (SWIFT_UNLIKELY(offset)) {
+    memcpy(dest + _addrOffset, src + _addrOffset, offset);
+  }
+  addrOffset = _addrOffset + offset;
   tag >>= 56;
   if (SWIFT_UNLIKELY(tag == 0)) {
     return;
@@ -1490,13 +1495,13 @@ static void singlePayloadEnumGenericAssignWithCopy(const Metadata *metadata,
       if (!srcTag) {
         srcTag = xiType->vw_getEnumTagSinglePayload(
             (const OpaqueValue *)(src + addrOffset + xiTagBytesOffset),
-            numEmptyCases);
+            xiType->vw_getNumExtraInhabitants());
       }
 
       if (!destTag) {
         destTag = xiType->vw_getEnumTagSinglePayload(
             (const OpaqueValue *)(dest + addrOffset + xiTagBytesOffset),
-            numEmptyCases);
+            xiType->vw_getNumExtraInhabitants());
       }
     }
 
@@ -2059,7 +2064,8 @@ swift_singlePayloadEnumGeneric_getEnumTag(swift::OpaqueValue *address,
                           uint8_t numExtraTagBytes) -> unsigned {
     if (xiType) {
       return xiType->vw_getEnumTagSinglePayload(
-          (const OpaqueValue *)(addr + xiTagBytesOffset), numEmptyCases);
+          (const OpaqueValue *)(addr + xiTagBytesOffset),
+          xiType->vw_getNumExtraInhabitants());
     }
 
     return 0;

test/Interpreter/Inputs/layout_string_witnesses_types.swift

@@ -543,6 +543,12 @@ public enum PrespecializedMultiPayloadEnum<T> {
     case nonEmpty1(T, Int)
 }
 
+public enum SinglePayloadEnumExistential {
+    case a(SomeProtocol, AnyObject)
+    case b
+    case c
+}
+
 @inline(never)
 public func consume<T>(_ x: T.Type) {
     withExtendedLifetime(x) {}
@@ -575,6 +581,10 @@ public func testAssign<T>(_ ptr: UnsafeMutablePointer<T>, from x: UnsafeMutableP
     ptr.assign(from: x, count: 1)
 }
 
+public func testAssignCopy<T>(_ ptr: UnsafeMutablePointer<T>, from x: inout T) {
+    ptr.update(from: &x, count: 1)
+}
+
 @inline(never)
 public func testInit<T>(_ ptr: UnsafeMutablePointer<T>, to x: T) {
     ptr.initialize(to: x)

test/Interpreter/layout_string_witnesses_static.swift

@@ -770,6 +770,43 @@ func testSinglePayloadEnumManyXIEmpty() {
 
 testSinglePayloadEnumManyXIEmpty()
 
+func testEnumWithExistential() {
+    // Regression test for rdar://117755666
+    // A missing call to memcpy in `handleSingleRefCountInitWithCopy`
+    // was causing unexpected behavior like wrong enum cases, crashes etc.
+    // Without the fix, this test would not release the references.
+    struct SomeProtocolImpl: SomeProtocol {
+        let x: AnyObject
+    }
+
+    let ptr = UnsafeMutablePointer<SinglePayloadEnumExistential>.allocate(capacity: 1)
+
+    do {
+        let x = SinglePayloadEnumExistential.b
+        testInit(ptr, to: x)
+    }
+
+    do {
+        var z = SinglePayloadEnumExistential.a(SomeProtocolImpl(x: SimpleClass(x: 23)), SimpleClass(x: 43))
+
+        // CHECK-NEXT: Before deinit
+        print("Before deinit")
+
+        testAssignCopy(ptr, from: &z)
+    }
+
+    // CHECK-NEXT: Before deinit
+    print("Before deinit")
+
+    // CHECK-NEXT: SimpleClass deinitialized!
+    // CHECK-NEXT: SimpleClass deinitialized!
+    testDestroy(ptr)
+
+    ptr.deallocate()
+}
+
+testEnumWithExistential()
+
 #if os(macOS)
 func testObjc() {
     let ptr = UnsafeMutablePointer<ObjcWrapper>.allocate(capacity: 1)