[IRGen] Distributed: Switch DistributedAccessor linking to reference underlying thunks

Preparing to start emitting distributed requirement accessors
that don't have `SILFunction *` because they are associated with
protocol requirements.

Author: xedin

include/swift/IRGen/Linking.h

@@ -359,6 +359,9 @@ class LinkEntity {
     /// the metadata cache once.
     CanonicalPrespecializedGenericTypeCachingOnceToken,
 
+    /// The function used to access distributed methods and accessors.
+    DistributedAccessor,
+
     /// The same as AsyncFunctionPointer but with a different stored value, for
     /// use by TBDGen.
     /// The pointer is an AbstractFunctionDecl*.
@@ -512,8 +515,6 @@ class LinkEntity {
     /// The pointer is a const char* of the name.
     KnownAsyncFunctionPointer,
 
-    /// The pointer is SILFunction*
-    DistributedAccessor,
     /// An async function pointer for a distributed accessor (method or
     /// property).
     /// The pointer is a SILFunction*.
@@ -1341,6 +1342,10 @@ class LinkEntity {
   }
 
   static LinkEntity forDistributedTargetAccessor(SILFunction *target) {
+    return forDistributedTargetAccessor(target->getDeclContext()->getAsDecl());
+  }
+
+  static LinkEntity forDistributedTargetAccessor(Decl *target) {
     LinkEntity entity;
     entity.Pointer = target;
     entity.SecondaryPointer = nullptr;

lib/IRGen/Linking.cpp

@@ -518,7 +518,7 @@ std::string LinkEntity::mangleAsString() const {
   }
 
   case Kind::DistributedAccessor: {
-    std::string Result(getSILFunction()->getName());
+    std::string Result = getSILDeclRef().mangle();
     Result.append("TF");
     return Result;
   }
@@ -554,6 +554,7 @@ SILDeclRef::Kind LinkEntity::getSILDeclRefKind() const {
   switch (getKind()) {
   case Kind::DispatchThunk:
   case Kind::MethodDescriptor:
+  case Kind::DistributedAccessor:
     return SILDeclRef::Kind::Func;
   case Kind::DispatchThunkInitializer:
   case Kind::MethodDescriptorInitializer:
@@ -571,7 +572,10 @@ SILDeclRef::Kind LinkEntity::getSILDeclRefKind() const {
 }
 
 SILDeclRef LinkEntity::getSILDeclRef() const {
-  return SILDeclRef(const_cast<ValueDecl *>(getDecl()), getSILDeclRefKind());
+  auto ref = SILDeclRef(const_cast<ValueDecl *>(getDecl()), getSILDeclRefKind());
+  if (getKind() == Kind::DistributedAccessor)
+    return ref.asDistributed();
+  return ref;
 }
 
 SILLinkage LinkEntity::getLinkage(ForDefinition_t forDefinition) const {
@@ -1306,8 +1310,7 @@ bool LinkEntity::isWeakImported(ModuleDecl *module) const {
     return false;
   case Kind::DynamicallyReplaceableFunctionKey:
   case Kind::DynamicallyReplaceableFunctionVariable:
-  case Kind::SILFunction:
-  case Kind::DistributedAccessor: {
+  case Kind::SILFunction: {
     return getSILFunction()->isWeakImported(module);
   }
 
@@ -1369,6 +1372,7 @@ bool LinkEntity::isWeakImported(ModuleDecl *module) const {
   case Kind::OpaqueTypeDescriptorAccessorImpl:
   case Kind::OpaqueTypeDescriptorAccessorKey:
   case Kind::OpaqueTypeDescriptorAccessorVar:
+  case Kind::DistributedAccessor:
     return getDecl()->isWeakImported(module);
 
   case Kind::CanonicalSpecializedGenericSwiftMetaclassStub:
@@ -1480,6 +1484,7 @@ DeclContext *LinkEntity::getDeclContextForEmission() const {
   case Kind::OpaqueTypeDescriptorAccessorKey:
   case Kind::OpaqueTypeDescriptorAccessorVar:
   case Kind::CanonicalPrespecializedGenericTypeCachingOnceToken:
+  case Kind::DistributedAccessor:
     return getDecl()->getDeclContext();
 
   case Kind::CanonicalSpecializedGenericSwiftMetaclassStub:
@@ -1555,7 +1560,6 @@ DeclContext *LinkEntity::getDeclContextForEmission() const {
     return getUnderlyingEntityForAsyncFunctionPointer()
         .getDeclContextForEmission();
 
-  case Kind::DistributedAccessor:
   case Kind::AccessibleFunctionRecord: {
     return getSILFunction()->getParentModule();
   }