[AST] NFC: Repack misc SILBoxType bits

Author: davezarzycki

include/swift/AST/Types.h

@@ -339,6 +339,13 @@ class alignas(1 << TypeAlignInBits) TypeBase {
   };
   NUMBITS(SILFunctionType, NumTypeBaseBits + 12);
 
+  struct SILBoxTypeBitfields {
+    unsigned : NumTypeBaseBits;
+    unsigned : 32 - NumTypeBaseBits; // unused / padding
+    unsigned NumGenericArgs : 32;
+  };
+  NUMBITS(SILBoxType, 64);
+
   struct AnyMetatypeTypeBitfields {
     unsigned : NumTypeBaseBits;
     /// The representation of the metatype.
@@ -379,6 +386,7 @@ class alignas(1 << TypeAlignInBits) TypeBase {
     TypeVariableTypeBitfields TypeVariableTypeBits;
     ArchetypeTypeBitfields ArchetypeTypeBits;
     SILFunctionTypeBitfields SILFunctionTypeBits;
+    SILBoxTypeBitfields SILBoxTypeBits;
     AnyMetatypeTypeBitfields AnyMetatypeTypeBits;
     ProtocolCompositionTypeBitfields ProtocolCompositionTypeBits;
     TupleTypeBitfields TupleTypeBits;
@@ -3806,7 +3814,6 @@ class SILBoxType final : public TypeBase,
   friend TrailingObjects;
 
   SILLayout *Layout;
-  unsigned NumGenericArgs;
 
   static RecursiveTypeProperties
   getRecursivePropertiesFromSubstitutions(SubstitutionList Args);
@@ -3822,7 +3829,7 @@ class SILBoxType final : public TypeBase,
   SILLayout *getLayout() const { return Layout; }
   SubstitutionList getGenericArgs() const {
     return llvm::makeArrayRef(getTrailingObjects<Substitution>(),
-                              NumGenericArgs);
+                              SILBoxTypeBits.NumGenericArgs);
   }
 
   // In SILType.h:

lib/AST/Type.cpp

@@ -4103,10 +4103,8 @@ void SILBoxType::Profile(llvm::FoldingSetNodeID &id, SILLayout *Layout,
 SILBoxType::SILBoxType(ASTContext &C,
                        SILLayout *Layout, SubstitutionList Args)
 : TypeBase(TypeKind::SILBox, &C,
-           getRecursivePropertiesFromSubstitutions(Args)),
-  Layout(Layout),
-  NumGenericArgs(Args.size())
-{
+           getRecursivePropertiesFromSubstitutions(Args)), Layout(Layout) {
+  SILBoxTypeBits.NumGenericArgs = Args.size();
 #ifndef NDEBUG
   // Check that the generic args are reasonable for the box's signature.
   if (Layout->getGenericSignature())
@@ -4115,9 +4113,8 @@ SILBoxType::SILBoxType(ASTContext &C,
     assert(arg.getReplacement()->isCanonical() &&
            "box arguments must be canonical types!");
 #endif
-  auto paramsBuf = getTrailingObjects<Substitution>();
-  for (unsigned i = 0; i < NumGenericArgs; ++i)
-    ::new (paramsBuf + i) Substitution(Args[i]);
+  std::uninitialized_copy(Args.begin(), Args.end(),
+                          getTrailingObjects<Substitution>());
 }
 
 RecursiveTypeProperties SILBoxType::