Future proof the initRawStructMetadata entrypoint

Author: Azoy

include/swift/ABI/MetadataValues.h

@@ -1525,6 +1525,29 @@ static inline bool isValueWitnessTableMutable(EnumLayoutFlags flags) {
   return uintptr_t(flags) & uintptr_t(EnumLayoutFlags::IsVWTMutable);
 }
 
+/// Flags for raw layout.
+enum class RawLayoutFlags : uintptr_t {
+  /// Whether or not we're initializing an array like raw layout type.
+  IsArray = 0x1,
+
+  /// Whether or not this raw layout type was declared 'movesAsLike'.
+  MovesAsLike = 0x2,
+};
+static inline RawLayoutFlags operator|(RawLayoutFlags lhs,
+                                       RawLayoutFlags rhs) {
+  return RawLayoutFlags(uintptr_t(lhs) | uintptr_t(rhs));
+}
+static inline RawLayoutFlags &operator|=(RawLayoutFlags &lhs,
+                                         RawLayoutFlags rhs) {
+  return (lhs = (lhs | rhs));
+}
+static inline bool isRawLayoutArray(RawLayoutFlags flags) {
+  return uintptr_t(flags) & uintptr_t(RawLayoutFlags::IsArray);
+}
+static inline bool shouldRawLayoutMoveAsLike(RawLayoutFlags flags) {
+  return uintptr_t(flags) & uintptr_t(RawLayoutFlags::MovesAsLike);
+}
+
 namespace SpecialPointerAuthDiscriminators {
   // All of these values are the stable string hash of the corresponding
   // variable name:

include/swift/Runtime/Metadata.h

@@ -1057,9 +1057,10 @@ void _swift_registerConcurrencyStandardTypeDescriptors(
 /// as the basis for the layout.
 SWIFT_RUNTIME_EXPORT
 void swift_initRawStructMetadata(StructMetadata *self,
-                                 StructLayoutFlags flags,
+                                 StructLayoutFlags structLayoutFlags,
                                  const TypeLayout *likeType,
-                                 ssize_t count);
+                                 ssize_t count,
+                                 RawLayoutFlags rawLayoutFlags);
 
 /// Check if the given generic arguments are valid inputs for the generic type
 /// context and if so call the metadata access function and return the metadata.

include/swift/Runtime/RuntimeFunctions.def

@@ -2823,14 +2823,16 @@ FUNCTION(GenericInstantiateLayoutString,
          UNKNOWN_MEMEFFECTS)
 
 // void swift_initRawStructMetadata(Metadata *structType,
-//                                  StructLayoutFlags flags,
+//                                  StructLayoutFlags structLayoutFlags,
 //                                  const TypeLayout *likeType,
-//                                  ssize_t count);
+//                                  ssize_t count,
+//                                  RawLayoutFlags rawLayoutFlags);
 FUNCTION(InitRawStructMetadata,
          swift_initRawStructMetadata,
          C_CC, AlwaysAvailable,
          RETURNS(VoidTy),
-         ARGS(TypeMetadataPtrTy, SizeTy, Int8PtrPtrTy->getPointerTo(0), SizeTy),
+         ARGS(TypeMetadataPtrTy, SizeTy, Int8PtrPtrTy->getPointerTo(0), SizeTy,
+              SizeTy),
          ATTRS(NoUnwind),
          EFFECT(MetaData),
          UNKNOWN_MEMEFFECTS)

lib/IRGen/GenMeta.cpp

@@ -3315,19 +3315,29 @@ static void emitInitializeRawLayout(IRGenFunction &IGF, SILType likeType,
   }
 
   auto &IGM = IGF.IGM;
+  auto rawLayout = T.getRawLayout();
   auto likeTypeLayout = emitTypeLayoutRef(IGF, likeType, collector);
-  StructLayoutFlags flags = StructLayoutFlags::Swift5Algorithm;
+  auto structLayoutflags = StructLayoutFlags::Swift5Algorithm;
+  RawLayoutFlags rawLayoutFlags;
+
+  if (rawLayout->shouldMoveAsLikeType())
+    rawLayoutFlags |= RawLayoutFlags::MovesAsLike;
 
-  // If we don't have a count, then we're the 'like:' variant and we need to
-  // pass '-1' to the runtime call.
+  // If we don't have a count, then we're the 'like:' variant so just pass some
+  // 0 to the runtime call.
   if (!count) {
-    count = llvm::ConstantInt::get(IGF.IGM.SizeTy, -1);
+    count = IGM.getSize(Size(0));
+  } else {
+    rawLayoutFlags |= RawLayoutFlags::IsArray;
   }
 
   // Call swift_initRawStructMetadata().
   IGF.Builder.CreateCall(IGM.getInitRawStructMetadataFunctionPointer(),
-                         {metadata, IGM.getSize(Size(uintptr_t(flags))),
-                          likeTypeLayout, count});
+                         {metadata,
+                          IGM.getSize(Size(uintptr_t(structLayoutflags))),
+                          likeTypeLayout,
+                          count,
+                          IGM.getSize(Size(uintptr_t(rawLayoutFlags)))});
 }
 
 static void emitInitializeValueMetadata(IRGenFunction &IGF,

stdlib/public/runtime/Metadata.cpp

@@ -3028,10 +3028,11 @@ void swift::_swift_addRefCountStringForMetatype(LayoutStringWriter &writer,
 /// Initialize the value witness table for a @_rawLayout struct.
 SWIFT_RUNTIME_EXPORT
 void swift::swift_initRawStructMetadata(StructMetadata *structType,
-                                        StructLayoutFlags layoutFlags,
+                                        StructLayoutFlags structLayoutFlags,
                                         const TypeLayout *likeTypeLayout,
-                                        ssize_t count) {
-  auto vwtable = getMutableVWTableForInit(structType, layoutFlags);
+                                        ssize_t count,
+                                        RawLayoutFlags rawLayoutFlags) {
+  auto vwtable = getMutableVWTableForInit(structType, structLayoutFlags);
 
   // The existing vwt function entries are all fine to preserve, the only thing
   // we need to initialize is the actual type layout.
@@ -3040,9 +3041,8 @@ void swift::swift_initRawStructMetadata(StructMetadata *structType,
   auto alignMask = likeTypeLayout->flags.getAlignmentMask();
   auto extraInhabitantCount = likeTypeLayout->extraInhabitantCount;
 
-  // If our count is not -1, we're dealing an array like layout.
-  if (count != -1) {
-    stride *= (size_t)count;
+  if (isRawLayoutArray(rawLayoutFlags)) {
+    stride *= std::min(count, (ssize_t)0);
     size = stride;
   }
 
@@ -3052,6 +3052,12 @@ void swift::swift_initRawStructMetadata(StructMetadata *structType,
                     .withAlignmentMask(alignMask)
                     .withCopyable(false);
   vwtable->extraInhabitantCount = extraInhabitantCount;
+
+  if (shouldRawLayoutMoveAsLike(rawLayoutFlags)) {
+    vwtable->flags = vwtable->flags
+                .withBitwiseTakable(likeTypeLayout->flags.isBitwiseTakable())
+                .withInlineStorage(likeTypeLayout->flags.isInlineStorage());
+  }
 }
 
 /***************************************************************************/