Improve layout strings runtime code and fix several issues

include/swift/ABI/Metadata.h

@@ -324,12 +324,8 @@ struct TargetMetadata {
 
   const uint8_t *getLayoutString() const {
     assert(hasLayoutString());
-    if (isAnyClass()) {
-      return asFullMetadata(
-                 reinterpret_cast<const TargetAnyClassMetadata<Runtime> *>(
-                     this))
-          ->layoutString;
-    }
+    // Classes should not have layout strings
+    assert(!isAnyClass());
     return asFullMetadata(this)->layoutString;
   }
 

lib/IRGen/GenMeta.cpp

@@ -2586,8 +2586,7 @@ void irgen::emitLazyTypeContextDescriptor(IRGenModule &IGM,
         IGM.Context.LangOpts.hasFeature(
             Feature::LayoutStringValueWitnessesInstantiation) &&
         IGM.getOptions().EnableLayoutStringValueWitnessesInstantiation) {
-      hasLayoutString |= requiresForeignTypeMetadata(type) ||
-                         needsSingletonMetadataInitialization(IGM, type) ||
+      hasLayoutString |= needsSingletonMetadataInitialization(IGM, type) ||
                          (type->isGenericContext() && !isa<FixedTypeInfo>(ti));
     }
   }

lib/IRGen/GenStruct.cpp

@@ -919,10 +919,10 @@ namespace {
             field.getTypeInfo().buildTypeLayoutEntry(IGM, fieldTy, useStructLayouts));
       }
 
-      if (fields.size() == 1 && isFixedSize() &&
-          getBestKnownAlignment() == *fields[0]->fixedAlignment(IGM)) {
-        return fields[0];
-      }
+      // if (fields.size() == 1 && isFixedSize() &&
+      //     getBestKnownAlignment() == *fields[0]->fixedAlignment(IGM)) {
+      //   return fields[0];
+      // }
 
       return IGM.typeLayoutCache.getOrCreateAlignedGroupEntry(
           fields, T, getBestKnownAlignment().getValue(), *this);

lib/IRGen/TypeLayout.cpp

@@ -160,7 +160,7 @@ class LayoutStringBuilder {
     RefCounting op;
     op.kind = RefCountingKind::SinglePayloadEnumFN;
     op.singlePayloadEnumFN.tagFn = tagFn;
-    op.singlePayloadEnumSimple.extraTagByteCount = extraTagByteCount;
+    op.singlePayloadEnumFN.extraTagByteCount = extraTagByteCount;
     op.singlePayloadEnumFN.payload = payload;
     refCountings.push_back(op);
   }
@@ -360,12 +360,19 @@ class LayoutStringBuilder {
         break;
       }
 
-      default: {
+      case RefCountingKind::Existential: {
         uint64_t op = (static_cast<uint64_t>(refCounting.kind) << 56) | skip;
         B.addInt64(op);
         refCountBytes += sizeof(uint64_t);
+        skip = refCounting.size - getFixedBufferSize(IGM).getValue();
+        break;
+      }
 
-        skip = refCounting.size;
+      default: {
+        uint64_t op = (static_cast<uint64_t>(refCounting.kind) << 56) | skip;
+        B.addInt64(op);
+        refCountBytes += sizeof(uint64_t);
+        skip = refCounting.size - IGM.getPointerSize().getValue();
         break;
       }
       }
@@ -1734,7 +1741,7 @@ AlignedGroupEntry::layoutString(IRGenModule &IGM,
 
 bool AlignedGroupEntry::refCountString(IRGenModule &IGM, LayoutStringBuilder &B,
                                        GenericSignature genericSig) const {
-  if (!isFixedSize(IGM)) {
+  if (!isFixedSize(IGM) || ty.isMoveOnly()) {
     return false;
   }
 

stdlib/public/runtime/Array.cpp

@@ -22,6 +22,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "BytecodeLayouts.h"
 #include "swift/Runtime/Config.h"
 #include "swift/Runtime/HeapObject.h"
 #include "swift/Runtime/Metadata.h"
@@ -124,6 +125,10 @@ static void array_copy_operation(OpaqueValue *dest, OpaqueValue *src,
   assert(copyKind == ArrayCopy::BackToFront);
   assert(count != 0);
 
+  if (self->hasLayoutString() && destOp == ArrayDest::Init && srcOp == ArraySource::Copy) {
+      return swift_generic_arrayInitWithCopy(dest, src, count, stride, self);
+  }
+
   auto copy = get_witness_function<destOp, srcOp>(wtable);
   size_t i = count;
   do {
@@ -202,6 +207,10 @@ void swift_arrayDestroy(OpaqueValue *begin, size_t count, const Metadata *self)
     return;
 
   auto stride = wtable->getStride();
+  if (self->hasLayoutString()) {
+      return swift_generic_arrayDestroy(begin, count, stride, self);
+  }
+
   for (size_t i = 0; i < count; ++i) {
     auto offset = i * stride;
     auto *obj = reinterpret_cast<OpaqueValue *>((char *)begin + offset);