[CoroutineAccessors] Use async bit in descriptors.

include/swift/ABI/MetadataValues.h

@@ -374,8 +374,6 @@ class MethodDescriptorFlags {
     Setter,
     ModifyCoroutine,
     ReadCoroutine,
-    Read2Coroutine,
-    Modify2Coroutine,
   };
 
 private:
@@ -438,23 +436,27 @@ class MethodDescriptorFlags {
   /// Note that 'init' is not considered an instance member.
   bool isInstance() const { return Value & IsInstanceMask; }
 
-  bool isAsync() const { return Value & IsAsyncMask; }
+  bool _hasAsyncBitSet() const { return Value & IsAsyncMask; }
 
-  bool isCalleeAllocatedCoroutine() const {
+  bool isAsync() const { return !isCoroutine() && _hasAsyncBitSet(); }
+
+  bool isCoroutine() const {
     switch (getKind()) {
     case Kind::Method:
     case Kind::Init:
     case Kind::Getter:
     case Kind::Setter:
+      return false;
     case Kind::ModifyCoroutine:
     case Kind::ReadCoroutine:
-      return false;
-    case Kind::Read2Coroutine:
-    case Kind::Modify2Coroutine:
       return true;
     }
   }
 
+  bool isCalleeAllocatedCoroutine() const {
+    return isCoroutine() && _hasAsyncBitSet();
+  }
+
   bool isData() const { return isAsync() || isCalleeAllocatedCoroutine(); }
 
   uint16_t getExtraDiscriminator() const {
@@ -615,8 +617,6 @@ class ProtocolRequirementFlags {
     ModifyCoroutine,
     AssociatedTypeAccessFunction,
     AssociatedConformanceAccessFunction,
-    Read2Coroutine,
-    Modify2Coroutine,
   };
 
 private:
@@ -666,26 +666,30 @@ class ProtocolRequirementFlags {
   /// Note that 'init' is not considered an instance member.
   bool isInstance() const { return Value & IsInstanceMask; }
 
-  bool isAsync() const { return Value & IsAsyncMask; }
+  bool _hasAsyncBitSet() const { return Value & IsAsyncMask; }
 
-  bool isCalleeAllocatedCoroutine() const {
+  bool isAsync() const { return !isCoroutine() && _hasAsyncBitSet(); }
+
+  bool isCoroutine() const {
     switch (getKind()) {
     case Kind::BaseProtocol:
     case Kind::Method:
     case Kind::Init:
     case Kind::Getter:
     case Kind::Setter:
-    case Kind::ReadCoroutine:
-    case Kind::ModifyCoroutine:
     case Kind::AssociatedTypeAccessFunction:
     case Kind::AssociatedConformanceAccessFunction:
       return false;
-    case Kind::Read2Coroutine:
-    case Kind::Modify2Coroutine:
+    case Kind::ReadCoroutine:
+    case Kind::ModifyCoroutine:
       return true;
     }
   }
 
+  bool isCalleeAllocatedCoroutine() const {
+    return isCoroutine() && _hasAsyncBitSet();
+  }
+
   bool isData() const { return isAsync() || isCalleeAllocatedCoroutine(); }
 
   bool isSignedWithAddress() const {

lib/IRGen/GenMeta.cpp

@@ -255,22 +255,24 @@ static Flags getMethodDescriptorFlags(ValueDecl *fn) {
     return flags;
   }
 
-  auto kind = [&] {
+  auto kindAndIsCalleeAllocatedCoroutine =
+      [&]() -> std::pair<typename Flags::Kind, bool> {
     auto accessor = dyn_cast<AccessorDecl>(fn);
-    if (!accessor) return Flags::Kind::Method;
+    if (!accessor)
+      return {Flags::Kind::Method, false};
     switch (accessor->getAccessorKind()) {
     case AccessorKind::Get:
-      return Flags::Kind::Getter;
+      return {Flags::Kind::Getter, false};
     case AccessorKind::Set:
-      return Flags::Kind::Setter;
+      return {Flags::Kind::Setter, false};
     case AccessorKind::Read:
-      return Flags::Kind::ReadCoroutine;
+      return {Flags::Kind::ReadCoroutine, false};
     case AccessorKind::Read2:
-      return Flags::Kind::Read2Coroutine;
+      return {Flags::Kind::ReadCoroutine, true};
     case AccessorKind::Modify:
-      return Flags::Kind::ModifyCoroutine;
+      return {Flags::Kind::ModifyCoroutine, false};
     case AccessorKind::Modify2:
-      return Flags::Kind::Modify2Coroutine;
+      return {Flags::Kind::ModifyCoroutine, true};
 #define OPAQUE_ACCESSOR(ID, KEYWORD)
 #define ACCESSOR(ID) \
     case AccessorKind::ID:
@@ -280,9 +282,20 @@ static Flags getMethodDescriptorFlags(ValueDecl *fn) {
     }
     llvm_unreachable("bad kind");
   }();
-  bool hasAsync = false;
+  auto kind = kindAndIsCalleeAllocatedCoroutine.first;
+
+  // Because no async old-ABI accessor coroutines exist or presumably ever will
+  // (if async coroutines accessors are added, they will presumably be new-ABI),
+  // the pairs {Flags::Kind::ReadCoroutine, isAsync} and
+  // {Flags::Kind::ModifyCoroutine, isAsync} can't mean "async old-ABI
+  // accessor coroutine".  As such, we repurpose that pair to mean "new-ABI
+  // accessor coroutine".  This has the important virtue of resulting in ptrauth
+  // authing/signing coro function pointers as data on old OSes where the bit
+  // means "async" and where adding new accessor kinds requires a back
+  // deployment library.
+  bool hasAsync = kindAndIsCalleeAllocatedCoroutine.second;
   if (auto *afd = dyn_cast<AbstractFunctionDecl>(fn))
-    hasAsync = afd->hasAsync();
+    hasAsync |= afd->hasAsync();
   return Flags(kind).withIsInstance(!fn->isStatic()).withIsAsync(hasAsync);
 }
 

stdlib/public/runtime/Metadata.cpp

@@ -6162,9 +6162,7 @@ static void initProtocolWitness(void **slot, void *witness,
   case ProtocolRequirementFlags::Kind::Getter:
   case ProtocolRequirementFlags::Kind::Setter:
   case ProtocolRequirementFlags::Kind::ReadCoroutine:
-  case ProtocolRequirementFlags::Kind::Read2Coroutine:
   case ProtocolRequirementFlags::Kind::ModifyCoroutine:
-  case ProtocolRequirementFlags::Kind::Modify2Coroutine:
     swift_ptrauth_init_code_or_data(slot, witness,
                                     reqt.Flags.getExtraDiscriminator(),
                                     !reqt.Flags.isData());
@@ -6205,9 +6203,7 @@ static void copyProtocolWitness(void **dest, void * const *src,
   case ProtocolRequirementFlags::Kind::Getter:
   case ProtocolRequirementFlags::Kind::Setter:
   case ProtocolRequirementFlags::Kind::ReadCoroutine:
-  case ProtocolRequirementFlags::Kind::Read2Coroutine:
   case ProtocolRequirementFlags::Kind::ModifyCoroutine:
-  case ProtocolRequirementFlags::Kind::Modify2Coroutine:
     swift_ptrauth_copy_code_or_data(
         dest, src, reqt.Flags.getExtraDiscriminator(), !reqt.Flags.isData(),
         /*allowNull*/ true); // NULL allowed for VFE (methods in the vtable