[IRGen] Give property behavior conformances protocol conformance descriptors.

Protocol conformance descriptors are recorded in witness tables and are
needed to evaluate associated type witnesses. Start creating them for
property behavior conformances, but don’t put them in the section used
for reflection.

Author: DougGregor

lib/IRGen/GenDecl.cpp

@@ -680,10 +680,7 @@ void IRGenModule::emitRuntimeRegistration() {
   }
 
   // Register Swift protocol conformances if we added any.
-  if (!ProtocolConformances.empty()) {
-
-    llvm::Constant *conformances = emitProtocolConformances();
-
+  if (llvm::Constant *conformances = emitProtocolConformances()) {
     llvm::Constant *beginIndices[] = {
       llvm::ConstantInt::get(Int32Ty, 0),
       llvm::ConstantInt::get(Int32Ty, 0),
@@ -2461,18 +2458,29 @@ void IRGenModule::addProtocolConformance(
 
 /// Emit the protocol conformance list and return it.
 llvm::Constant *IRGenModule::emitProtocolConformances() {
-  // Do nothing if the list is empty.
-  if (ProtocolConformances.empty())
+  // Emit the conformances.
+  bool anyReflectedConformances = false;
+  for (auto *conformance : ProtocolConformances) {
+    // Emit the protocol conformance now.
+    emitProtocolConformance(conformance);
+
+    if (conformance->isBehaviorConformance())
+      continue;
+
+    anyReflectedConformances = true;
+  }
+
+  if (!anyReflectedConformances)
     return nullptr;
 
   // Define the global variable for the conformance list.
-
   ConstantInitBuilder builder(*this);
   auto descriptorArray = builder.beginArray(RelativeAddressTy);
 
   for (auto *conformance : ProtocolConformances) {
-    // Emit the protocol conformance now.
-    emitProtocolConformance(conformance);
+    // Behavior conformances cannot be reflected.
+    if (conformance->isBehaviorConformance())
+      continue;
 
     auto entity = LinkEntity::forProtocolConformanceDescriptor(conformance);
     auto descriptor =

lib/IRGen/GenProto.cpp

@@ -1267,13 +1267,9 @@ llvm::Value *uniqueForeignWitnessTableRef(IRGenFunction &IGF,
     /// Add reference to the protocol conformance descriptor that generated
     /// this table.
     void addProtocolConformanceDescriptor() {
-      if (Conformance.isBehaviorConformance()) {
-        Table.addNullPointer(IGM.Int8PtrTy);
-      } else {
-        auto descriptor =
-          IGM.getAddrOfProtocolConformanceDescriptor(&Conformance);
-        Table.addBitCast(descriptor, IGM.Int8PtrTy);
-      }
+      auto descriptor =
+        IGM.getAddrOfProtocolConformanceDescriptor(&Conformance);
+      Table.addBitCast(descriptor, IGM.Int8PtrTy);
     }
 
     /// A base protocol is witnessed by a pointer to the conformance
@@ -2483,12 +2479,12 @@ void IRGenModule::emitSILWitnessTable(SILWitnessTable *wt) {
   // Always emit an accessor function.
   wtableBuilder.buildAccessFunction(global);
 
+  addProtocolConformance(conf);
+
   // Behavior conformances can't be reflected.
   if (conf->isBehaviorConformance())
     return;
 
-  addProtocolConformance(conf);
-
   // Trigger the lazy emission of the foreign type metadata.
   CanType conformingType = conf->getType()->getCanonicalType();
   if (requiresForeignTypeMetadata(conformingType)) {