Generalize extra inhabitants of tuples.

Like we did for structs, make it so that tuple types can also get extra inhabitants from whichever element with the most, not only the first. This lets us move all of the extra inhabitant handling functionality between structs and tuples in IRGen up to the common RecordTypeInfo CRTP base.

Author: jckarter

foo.swift

@@ -0,0 +1,25 @@
+
+enum SinglePayloadGenericEnumWithDefaultMirror<T, U> {
+  case Well
+  case Faucet
+  case Pipe(T, U)
+}
+
+func foo(x: Int, y: [Int], out: (SinglePayloadGenericEnumWithDefaultMirror<Int, [Int]>) -> ()) {
+  out(.Well)
+  out(.Faucet)
+  out(.Pipe(x, y))
+}
+
+func bar<T, U>(_ x: SinglePayloadGenericEnumWithDefaultMirror<T, U>) {
+  switch x {
+  case .Well:
+    print("well")
+  case .Faucet:
+    print("faucet")
+  case .Pipe:
+    print("pipe")
+  }
+}
+
+foo(x: 1, y: [1,2,3], out: bar)

include/swift/ABI/Metadata.h

@@ -1443,7 +1443,7 @@ struct TargetTupleTypeMetadata : public TargetMetadata<Runtime> {
   using StoredSize = typename Runtime::StoredSize;
   TargetTupleTypeMetadata() = default;
   constexpr TargetTupleTypeMetadata(const TargetMetadata<Runtime> &base,
-                                    StoredSize numElements,
+                                    uint32_t numElements,
                                     TargetPointer<Runtime, const char> labels)
     : TargetMetadata<Runtime>(base),
       NumElements(numElements),
@@ -1487,14 +1487,19 @@ struct TargetTupleTypeMetadata : public TargetMetadata<Runtime> {
     return getElements()[i];
   }
 
-  static constexpr StoredSize OffsetToNumElements = sizeof(TargetMetadata<Runtime>);
-
+  static constexpr StoredSize getOffsetToNumElements();
   static bool classof(const TargetMetadata<Runtime> *metadata) {
     return metadata->getKind() == MetadataKind::Tuple;
   }
 };
 using TupleTypeMetadata = TargetTupleTypeMetadata<InProcess>;
 
+template <typename Runtime>
+constexpr inline auto
+TargetTupleTypeMetadata<Runtime>::getOffsetToNumElements() -> StoredSize {
+  return offsetof(TargetTupleTypeMetadata<Runtime>, NumElements);
+}
+
 template <typename Runtime> struct TargetProtocolDescriptor;
 
 #if SWIFT_OBJC_INTEROP

include/swift/ABI/MetadataValues.h

@@ -244,7 +244,6 @@ class TargetExtraInhabitantFlags {
 
 public:
   constexpr TargetExtraInhabitantFlags() : Data(0) {}
-
   /// The number of extra inhabitants in the type's representation.
   int getNumExtraInhabitants() const { return Data & NumExtraInhabitantsMask; }
 

include/swift/Remote/MetadataReader.h

@@ -1087,8 +1087,8 @@ class MetadataReader {
         return _readMetadata<TargetStructMetadata>(address);
       case MetadataKind::Tuple: {
         auto numElementsAddress = address +
-          TargetTupleTypeMetadata<Runtime>::OffsetToNumElements;
-        StoredSize numElements;
+          TargetTupleTypeMetadata<Runtime>::getOffsetToNumElements();
+        uint32_t numElements;
         if (!Reader->readInteger(RemoteAddress(numElementsAddress),
                                  &numElements))
           return nullptr;