Merge pull request #8104 from rjmccall/farewell-to-archetype-access-paths

IRGen's archetype access path hack is now dead code, RIP.  NFC.

Author: rjmccall

lib/IRGen/GenArchetype.h

@@ -35,10 +35,6 @@ namespace irgen {
   using GetTypeParameterInContextFn =
     llvm::function_ref<CanType(CanType type)>;
 
-  void bindArchetypeAccessPaths(IRGenFunction &IGF,
-                                GenericSignature *generics,
-                                GetTypeParameterInContextFn getInContext);
-
   /// Emit a type metadata reference for an archetype.
   llvm::Value *emitArchetypeTypeMetadataRef(IRGenFunction &IGF,
                                             CanArchetypeType archetype);

lib/IRGen/GenMeta.cpp

@@ -2789,18 +2789,6 @@ irgen::emitFieldTypeAccessor(IRGenModule &IGM,
   // use it to provide metadata for generic parameters in field types.
   IGF.bindLocalTypeDataFromTypeMetadata(formalType, IsExact, metadata);
 
-  // Bind archetype access paths if the type is generic.
-  if (type->isGenericContext()) {
-    auto declCtxt = type;
-    if (auto generics = declCtxt->getGenericSignatureOfContext()) {
-      auto getInContext = [&](CanType type) -> CanType {
-        return declCtxt->mapTypeIntoContext(type)
-            ->getCanonicalType();
-      };
-      bindArchetypeAccessPaths(IGF, generics, getInContext);
-    }
-  }
-
   // Allocate storage for the field vector.
   unsigned allocSize = fieldTypes.size() * IGM.getPointerSize().getValue();
   auto allocSizeVal = llvm::ConstantInt::get(IGM.IntPtrTy, allocSize);

lib/IRGen/GenProto.cpp

@@ -1222,16 +1222,6 @@ class AccessorConformanceInfo : public ConformanceInfo {
       }
       return *Fulfillments;
     }
-
-    void bindArchetypeAccessPathsInConformance(IRGenFunction &IGF) {
-      auto declCtx = Conformance.getDeclContext();
-      if (auto generics = declCtx->getGenericSignatureOfContext()) {
-        auto getInContext = [&](CanType type) -> CanType {
-          return declCtx->mapTypeIntoContext(type)->getCanonicalType();
-        };
-        bindArchetypeAccessPaths(IGF, generics, getInContext);
-      }
-    }
   };
 } // end anonymous namespace
 
@@ -1286,9 +1276,6 @@ getAssociatedTypeMetadataAccessFunction(AssociatedTypeDecl *requirement,
   // Bind local type data from the metadata argument.
   IGF.bindLocalTypeDataFromTypeMetadata(ConcreteType, IsExact, self);
 
-  // Bind archetype access paths.
-  bindArchetypeAccessPathsInConformance(IGF);
-
   // For now, assume that an associated type is cheap enough to access
   // that it doesn't need a new cache entry.
   if (auto archetype = dyn_cast<ArchetypeType>(associatedType)) {
@@ -1426,9 +1413,6 @@ getAssociatedTypeWitnessTableAccessFunction(CanType depAssociatedType,
                                         associatedTypeMetadata);
   IGF.bindLocalTypeDataFromTypeMetadata(ConcreteType, IsExact, self);
 
-  // Bind archetype access paths.
-  bindArchetypeAccessPathsInConformance(IGF);
-
   // For now, assume that finding an abstract conformance is always
   // fast enough that it's not worth caching.
   // TODO: provide an API to find the best metadata path to the conformance
@@ -1787,58 +1771,6 @@ bool irgen::hasPolymorphicParameters(CanSILFunctionType ty) {
   llvm_unreachable("Not a valid SILFunctionTypeRepresentation.");
 }
 
-static
-void addPotentialArchetypeAccessPath(IRGenFunction &IGF,
-                                     CanType targetDepType,
-                                     CanType sourceDepType,
-                                     GetTypeParameterInContextFn getInContext) {
-  assert(targetDepType->isTypeParameter());
-  assert(sourceDepType->isTypeParameter());
-
-  // We can only break down an associated-type path.
-  auto sourceDepMemberType = dyn_cast<DependentMemberType>(sourceDepType);
-  if (!sourceDepMemberType) return;
-
-  // We only really need to do this when there's a non-trivial set of
-  // conformances, but we can't determine that just from this decl:
-  // the associated type might gain conformances in a refining protocol.
-  auto association = sourceDepMemberType->getAssocType();
-
-  // These can end up as non-archetypes because of multiple levels of
-  // equality.
-  auto destArchetype =
-    dyn_cast<ArchetypeType>(getInContext(targetDepType));
-  if (!destArchetype) return;
-  auto srcBaseArchetype =
-    dyn_cast<ArchetypeType>(getInContext(sourceDepMemberType.getBase()));
-  if (!srcBaseArchetype) return;
-
-  IGF.addArchetypeAccessPath(destArchetype,
-                             {srcBaseArchetype, association});
-}
-
-void irgen::bindArchetypeAccessPaths(IRGenFunction &IGF, GenericSignature *Generics,
-                              GetTypeParameterInContextFn getInContext) {
-  // Remember all the extra ways we have of reaching the parameter
-  // archetypes due to type equality constraints.
-  for (auto reqt : Generics->getRequirements()) {
-    // Ignore non-same-type requirements in this pass.
-    if (reqt.getKind() != RequirementKind::SameType) continue;
-
-    // Ignore equality constraints to concrete types.  This is really
-    // just a fast-path; we still have to handle this case later.
-    // TODO: This might be a faster / better-cached way to materialize
-    // local type data for the concrete type.
-    if (!reqt.getSecondType()->isTypeParameter()) continue;
-
-    auto firstType = reqt.getFirstType()->getCanonicalType();
-    auto secondType = reqt.getSecondType()->getCanonicalType();
-
-    addPotentialArchetypeAccessPath(IGF, firstType, secondType, getInContext);
-    addPotentialArchetypeAccessPath(IGF, secondType, firstType, getInContext);
-  }
-}
-
 /// Emit a polymorphic parameters clause, binding all the metadata necessary.
 void EmitPolymorphicParameters::emit(Explosion &in,
                                      WitnessMetadata *witnessMetadata,
@@ -1860,29 +1792,8 @@ void EmitPolymorphicParameters::emit(Explosion &in,
 
   // Bind all the fulfillments we can from the formal parameters.
   bindParameterSources(getParameter);
-
-  if (!Generics) return;
-  
-  // Bind all the archetype access paths.
-  bindArchetypeAccessPaths(IGF, Generics, getInContext);
-}
-
-void IRGenFunction::addArchetypeAccessPath(CanArchetypeType targetArchetype,
-                                           ArchetypeAccessPath accessPath) {
-  ArchetypeAccessPaths[targetArchetype].push_back(accessPath);
 }
 
-ArrayRef<IRGenFunction::ArchetypeAccessPath>
-IRGenFunction::getArchetypeAccessPaths(CanArchetypeType targetArchetype) {
-  auto it = ArchetypeAccessPaths.find(targetArchetype);
-  if (it == ArchetypeAccessPaths.end()) {
-    return {};
-  } else {
-    return it->second;
-  }
-}
-
-
 llvm::Value *
 MetadataPath::followFromTypeMetadata(IRGenFunction &IGF,
                                      CanType sourceType,
@@ -2716,12 +2627,6 @@ void GenericTypeRequirements::bindFromBuffer(IRGenFunction &IGF,
                                              Address buffer,
                                     GetTypeParameterInContextFn getInContext) {
   bindFromGenericRequirementsBuffer(IGF, Requirements, buffer, getInContext);
-
-  auto Generics = TheDecl->getGenericSignature();
-  if (!Generics) return;
-
-  // Bind all the archetype access paths in the signature's requirements.
-  bindArchetypeAccessPaths(IGF, Generics, getInContext);
 }
 
 void irgen::bindFromGenericRequirementsBuffer(IRGenFunction &IGF,

lib/IRGen/IRGenFunction.h

@@ -394,23 +394,6 @@ class IRGenFunction {
                      llvm::Value *metadata,
                      ArrayRef<llvm::Value*> wtables);
 
-  struct ArchetypeAccessPath {
-    CanArchetypeType BaseType;
-    AssociatedTypeDecl *Association;
-  };
-
-  /// Register an additional access path to the given archetype besides
-  /// (if applicable) just drilling down from its parent.
-  ///
-  /// This is necessary when an archetype gains conformances from an
-  /// associated type that it's been constrained to be equal to
-  /// but which is not simply its parent.
-  void addArchetypeAccessPath(CanArchetypeType targetArchetype,
-                              ArchetypeAccessPath accessPath);
-
-  ArrayRef<ArchetypeAccessPath>
-  getArchetypeAccessPaths(CanArchetypeType targetArchetype);
-
 //--- Type emission ------------------------------------------------------------
 public:
   /// Look up a local type data reference, returning null if no entry was
@@ -581,9 +564,6 @@ class IRGenFunction {
   llvm::Value *LocalSelf = nullptr;
 
   LocalSelfKind SelfKind;
-
-  llvm::DenseMap<CanType, std::vector<ArchetypeAccessPath>>
-  ArchetypeAccessPaths;
 };
 
 using ConditionalDominanceScope = IRGenFunction::ConditionalDominanceScope;