AST: Optimize storage of VersionTuples in AvailableAttr.

Representing introduced, deprecated, and obsoleted versions at rest as optional
version tuples is redundant, since the empty version tuple already represents
"version not present".

NFC.

Author: tshortli

include/swift/AST/Attr.h

@@ -754,26 +754,32 @@ class AvailableAttr : public DeclAttribute {
   const StringRef Message;
   const StringRef Rename;
 
-  const std::optional<llvm::VersionTuple> Introduced;
+  const llvm::VersionTuple Introduced;
   const SourceRange IntroducedRange;
-  const std::optional<llvm::VersionTuple> Deprecated;
+  const llvm::VersionTuple Deprecated;
   const SourceRange DeprecatedRange;
-  const std::optional<llvm::VersionTuple> Obsoleted;
+  const llvm::VersionTuple Obsoleted;
   const SourceRange ObsoletedRange;
 
 public:
   /// Returns the parsed version for `introduced:`.
   std::optional<llvm::VersionTuple> getRawIntroduced() const {
+    if (Introduced.empty())
+      return std::nullopt;
     return Introduced;
   }
 
   /// Returns the parsed version for `deprecated:`.
   std::optional<llvm::VersionTuple> getRawDeprecated() const {
+    if (Deprecated.empty())
+      return std::nullopt;
     return Deprecated;
   }
 
   /// Returns the parsed version for `obsoleted:`.
   std::optional<llvm::VersionTuple> getRawObsoleted() const {
+    if (Obsoleted.empty())
+      return std::nullopt;
     return Obsoleted;
   }
 
@@ -3268,7 +3274,7 @@ class SemanticAvailableAttr final {
 
   /// The version tuple written in source for the `introduced:` component.
   std::optional<llvm::VersionTuple> getIntroduced() const {
-    return attr->Introduced;
+    return attr->getRawIntroduced();
   }
 
   /// The source range of the `introduced:` component.
@@ -3280,12 +3286,12 @@ class SemanticAvailableAttr final {
 
   /// The version tuple written in source for the `deprecated:` component.
   std::optional<llvm::VersionTuple> getDeprecated() const {
-    return attr->Deprecated;
+    return attr->getRawDeprecated();
   }
 
   /// The version tuple written in source for the `obsoleted:` component.
   std::optional<llvm::VersionTuple> getObsoleted() const {
-    return attr->Obsoleted;
+    return attr->getRawObsoleted();
   }
 
   /// Returns the `message:` field of the attribute, or an empty string.
@@ -3318,7 +3324,8 @@ class SemanticAvailableAttr final {
   /// Whether this attribute has an introduced, deprecated, or obsoleted
   /// version.
   bool isVersionSpecific() const {
-    return attr->Introduced || attr->Deprecated || attr->Obsoleted;
+    return getIntroduced().has_value() || getDeprecated().has_value() ||
+           getObsoleted().has_value();
   }
 
   /// Whether this is a language mode specific attribute.

lib/AST/Attr.cpp

@@ -2108,8 +2108,6 @@ Type RawLayoutAttr::getResolvedCountType(StructDecl *sd) const {
                            ErrorType::get(ctx));
 }
 
-#define INIT_VER_TUPLE(X) X(X.empty() ? std::optional<llvm::VersionTuple>() : X)
-
 AvailableAttr::AvailableAttr(
     SourceLoc AtLoc, SourceRange Range, const AvailabilityDomain &Domain,
     Kind Kind, StringRef Message, StringRef Rename,
@@ -2118,10 +2116,10 @@ AvailableAttr::AvailableAttr(
     const llvm::VersionTuple &Obsoleted, SourceRange ObsoletedRange,
     bool Implicit, bool IsSPI)
     : DeclAttribute(DeclAttrKind::Available, AtLoc, Range, Implicit),
-      Domain(Domain), Message(Message), Rename(Rename),
-      INIT_VER_TUPLE(Introduced), IntroducedRange(IntroducedRange),
-      INIT_VER_TUPLE(Deprecated), DeprecatedRange(DeprecatedRange),
-      INIT_VER_TUPLE(Obsoleted), ObsoletedRange(ObsoletedRange) {
+      Domain(Domain), Message(Message), Rename(Rename), Introduced(Introduced),
+      IntroducedRange(IntroducedRange), Deprecated(Deprecated),
+      DeprecatedRange(DeprecatedRange), Obsoleted(Obsoleted),
+      ObsoletedRange(ObsoletedRange) {
   Bits.AvailableAttr.Kind = static_cast<uint8_t>(Kind);
   Bits.AvailableAttr.HasComputedSemanticAttr = false;
   Bits.AvailableAttr.HasDomain = true;
@@ -2130,8 +2128,6 @@ AvailableAttr::AvailableAttr(
   Bits.AvailableAttr.IsSPI = IsSPI;
 }
 
-#undef INIT_VER_TUPLE
-
 AvailableAttr *AvailableAttr::createUniversallyUnavailable(ASTContext &C,
                                                            StringRef Message,
                                                            StringRef Rename) {
@@ -2199,12 +2195,9 @@ bool BackDeployedAttr::isActivePlatform(const ASTContext &ctx,
 AvailableAttr *AvailableAttr::clone(ASTContext &C, bool implicit) const {
   return new (C) AvailableAttr(
       implicit ? SourceLoc() : AtLoc, implicit ? SourceRange() : getRange(),
-      Domain, getKind(), Message, Rename,
-      Introduced ? *Introduced : llvm::VersionTuple(),
-      implicit ? SourceRange() : IntroducedRange,
-      Deprecated ? *Deprecated : llvm::VersionTuple(),
-      implicit ? SourceRange() : DeprecatedRange,
-      Obsoleted ? *Obsoleted : llvm::VersionTuple(),
+      Domain, getKind(), Message, Rename, Introduced,
+      implicit ? SourceRange() : IntroducedRange, Deprecated,
+      implicit ? SourceRange() : DeprecatedRange, Obsoleted,
       implicit ? SourceRange() : ObsoletedRange, implicit, isSPI());
 }
 
@@ -2294,7 +2287,7 @@ SemanticAvailableAttr::getVersionAvailability(const ASTContext &ctx) const {
     return AvailableVersionComparison::Unavailable;
 
   llvm::VersionTuple queryVersion = getActiveVersion(ctx);
-  std::optional<llvm::VersionTuple> ObsoletedVersion = attr->Obsoleted;
+  std::optional<llvm::VersionTuple> ObsoletedVersion = getObsoleted();
 
   StringRef ObsoletedPlatform;
   llvm::VersionTuple RemappedObsoletedVersion;
@@ -2307,7 +2300,7 @@ SemanticAvailableAttr::getVersionAvailability(const ASTContext &ctx) const {
   if (ObsoletedVersion && *ObsoletedVersion <= queryVersion)
     return AvailableVersionComparison::Obsoleted;
 
-  std::optional<llvm::VersionTuple> IntroducedVersion = attr->Introduced;
+  std::optional<llvm::VersionTuple> IntroducedVersion = getIntroduced();
   StringRef IntroducedPlatform;
   llvm::VersionTuple RemappedIntroducedVersion;
   if (AvailabilityInference::updateIntroducedPlatformForFallback(

lib/AST/Availability.cpp

@@ -794,10 +794,10 @@ SemanticAvailableAttr::getIntroducedRange(const ASTContext &Ctx) const {
   assert(getDomain().isActive(Ctx));
 
   auto *attr = getParsedAttr();
-  if (!attr->Introduced.has_value())
+  if (!attr->getRawIntroduced().has_value())
     return AvailabilityRange::alwaysAvailable();
 
-  llvm::VersionTuple IntroducedVersion = attr->Introduced.value();
+  llvm::VersionTuple IntroducedVersion = attr->getRawIntroduced().value();
   StringRef Platform;
   llvm::VersionTuple RemappedIntroducedVersion;
   if (AvailabilityInference::updateIntroducedPlatformForFallback(