AST: Store the IsSPI bit of AvailableAttr inline in DecAttribute.

Reduces the layout requirements for `AvailableAttr` by one byte.

Author: tshortli

include/swift/AST/Attr.h

@@ -147,6 +147,11 @@ class DeclAttribute : public AttributeBase {
       Value : 32
     );
 
+    SWIFT_INLINE_BITFIELD(AvailableAttr, DeclAttribute, 1,
+      /// Whether this attribute was spelled `@_spi_available`.
+      IsSPI : 1
+    );
+
     SWIFT_INLINE_BITFIELD(ClangImporterSynthesizedTypeAttr, DeclAttribute, 1,
       kind : 1
     );
@@ -690,7 +695,9 @@ class AvailableAttr : public DeclAttribute {
         INIT_VER_TUPLE(Introduced), IntroducedRange(IntroducedRange),
         INIT_VER_TUPLE(Deprecated), DeprecatedRange(DeprecatedRange),
         INIT_VER_TUPLE(Obsoleted), ObsoletedRange(ObsoletedRange),
-        PlatformAgnostic(PlatformAgnostic), Platform(Platform), IsSPI(IsSPI) {}
+        PlatformAgnostic(PlatformAgnostic), Platform(Platform) {
+    Bits.AvailableAttr.IsSPI = IsSPI;
+  }
 
 #undef INIT_VER_TUPLE
 
@@ -735,9 +742,6 @@ class AvailableAttr : public DeclAttribute {
   /// The platform of the availability.
   const PlatformKind Platform;
 
-  /// Whether this is available as SPI.
-  const bool IsSPI;
-
   /// Whether this is a language-version-specific entity.
   bool isLanguageVersionSpecific() const;
 
@@ -753,6 +757,9 @@ class AvailableAttr : public DeclAttribute {
   /// Whether this is a noasync attribute.
   bool isNoAsync() const;
 
+  /// Whether this attribute was spelled `@_spi_available`.
+  bool isSPI() const { return Bits.AvailableAttr.IsSPI; }
+
   /// Returns the platform-agnostic availability.
   PlatformAgnosticAvailabilityKind getPlatformAgnosticAvailability() const {
     return PlatformAgnostic;

lib/AST/Attr.cpp

@@ -662,7 +662,7 @@ static bool isShortAvailable(const DeclAttribute *DA) {
   if (!AvailAttr)
     return false;
 
-  if (AvailAttr->IsSPI)
+  if (AvailAttr->isSPI())
     return false;
 
   if (!AvailAttr->Introduced.has_value())
@@ -1371,7 +1371,7 @@ bool DeclAttribute::printImpl(ASTPrinter &Printer, const PrintOptions &Options,
     auto Attr = cast<AvailableAttr>(this);
     if (Options.SuppressNoAsyncAvailabilityAttr && Attr->isNoAsync())
       return false;
-    if (Options.printPublicInterface() && Attr->IsSPI) {
+    if (Options.printPublicInterface() && Attr->isSPI()) {
       assert(Attr->hasPlatform());
       assert(Attr->Introduced.has_value());
       Printer.printAttrName("@available");
@@ -1380,7 +1380,7 @@ bool DeclAttribute::printImpl(ASTPrinter &Printer, const PrintOptions &Options,
       Printer << ", unavailable)";
       break;
     }
-    if (Attr->IsSPI) {
+    if (Attr->isSPI()) {
       std::string atSPI = (llvm::Twine("@") + SPI_AVAILABLE_ATTRNAME).str();
       Printer.printAttrName(atSPI);
     } else {
@@ -2294,7 +2294,7 @@ AvailableAttr *AvailableAttr::clone(ASTContext &C, bool implicit) const {
                                implicit ? SourceRange() : ObsoletedRange,
                                PlatformAgnostic,
                                implicit,
-                               IsSPI);
+                               isSPI());
 }
 
 std::optional<OriginallyDefinedInAttr::ActiveVersion>

lib/AST/Availability.cpp

@@ -114,7 +114,7 @@ static void mergeWithInferredAvailability(const AvailableAttr *Attr,
 
   // The merge of two introduction versions is the maximum of the two versions.
   if (mergeIntoInferredVersion(Attr->Introduced, Inferred.Introduced, std::max)) {
-    Inferred.IsSPI = Attr->IsSPI;
+    Inferred.IsSPI = Attr->isSPI();
   }
 
   // The merge of deprecated and obsoleted versions takes the minimum.
@@ -596,7 +596,7 @@ AvailabilityRange AvailabilityInference::availableRange(const Decl *D) {
 
 bool AvailabilityInference::isAvailableAsSPI(const Decl *D) {
   if (auto attr = attrForAvailableRange(D))
-    return attr->IsSPI;
+    return attr->isSPI();
 
   return false;
 }

lib/Sema/TypeCheckAttr.cpp

@@ -2105,7 +2105,7 @@ void AttributeChecker::visitAvailableAttr(AvailableAttr *attr) {
     return;
 
   // FIXME: This seems like it could be diagnosed during parsing instead.
-  while (attr->IsSPI) {
+  while (attr->isSPI()) {
     if (attr->hasPlatform() && attr->Introduced.has_value())
       break;
     diagnoseAndRemoveAttr(attr, diag::spi_available_malformed);
@@ -4673,7 +4673,7 @@ void AttributeChecker::checkAvailableAttrs(ArrayRef<AvailableAttr *> Attrs) {
   if (!D->getDeclContext()->getInnermostDeclarationDeclContext()) {
     // If all available are spi available, we should use @_spi instead.
     if (std::all_of(Attrs.begin(), Attrs.end(), [](AvailableAttr *AV) {
-      return AV->IsSPI;
+      return AV->isSPI();
     })) {
       diagnose(D->getLoc(), diag::spi_preferred_over_spi_available);
     }

lib/Sema/TypeCheckConcurrency.cpp

@@ -6604,7 +6604,7 @@ static void addUnavailableAttrs(ExtensionDecl *ext, NominalTypeDecl *nominal) {
           available->Obsoleted.value_or(noVersion), SourceRange(),
           PlatformAgnosticAvailabilityKind::Unavailable,
           /*implicit=*/true,
-          available->IsSPI);
+          available->isSPI());
       ext->getAttrs().add(attr);
       anyPlatformSpecificAttrs = true;
     }

lib/Serialization/Serialization.cpp

@@ -3031,7 +3031,7 @@ class Serializer::DeclSerializer : public DeclVisitor<DeclSerializer> {
           theAttr->isUnconditionallyDeprecated(),
           theAttr->isNoAsync(),
           theAttr->isPackageDescriptionVersionSpecific(),
-          theAttr->IsSPI,
+          theAttr->isSPI(),
           LIST_VER_TUPLE_PIECES(Introduced),
           LIST_VER_TUPLE_PIECES(Deprecated),
           LIST_VER_TUPLE_PIECES(Obsoleted),