IRGen: handle static imports in deserialised modules

This showed up when trying to convert swift-package-manager to build
using static linking on Windows.  We would not correctly identify the
module as being static due to there being no DeclContext for emission.

Author: compnerd

include/swift/SIL/SILFunction.h

@@ -315,6 +315,9 @@ class SILFunction
   /// The function's effects attribute.
   unsigned EffectsKindAttr : NumEffectsKindBits;
 
+  /// The function is in a statically linked module.
+  unsigned IsStaticallyLinked : 1;
+
   static void
   validateSubclassScope(SubclassScope scope, IsThunk_t isThunk,
                         const GenericSpecializationInformation *genericInfo) {
@@ -534,6 +537,12 @@ class SILFunction
     WasDeserializedCanonical = val;
   }
 
+  bool isStaticallyLinked() const { return IsStaticallyLinked; }
+
+  void setIsStaticallyLinked(bool value) {
+    IsStaticallyLinked = value;
+  }
+
   /// Returns true if this is a reabstraction thunk of escaping function type
   /// whose single argument is a potentially non-escaping closure. i.e. the
   /// thunks' function argument may itself have @inout_aliasable parameters.

lib/IRGen/GenDecl.cpp

@@ -2055,13 +2055,20 @@ LinkInfo LinkInfo::get(const UniversalLinkageInfo &linkInfo,
                        const LinkEntity &entity,
                        ForDefinition_t isDefinition) {
   LinkInfo result;
+  entity.mangle(result.Name);
 
   bool isKnownLocal = entity.isAlwaysSharedLinkage();
-  if (const auto *DC = entity.getDeclContextForEmission())
+  if (const auto *DC = entity.getDeclContextForEmission()) {
     if (const auto *MD = DC->getParentModule())
       isKnownLocal = MD == swiftModule || MD->isStaticLibrary();
+  } else if (entity.hasSILFunction()) {
+    // SIL serialized entitites (functions, witness tables, vtables) do not have
+    // an associated DeclContext and are serialized into the current module.  As
+    // a result, we explicitly handle SIL Functions here. We do not expect other
+    // types to be referenced directly.
+    isKnownLocal = entity.getSILFunction()->isStaticallyLinked();
+  }
 
-  entity.mangle(result.Name);
   bool weakImported = entity.isWeakImported(swiftModule);
   result.IRL = getIRLinkage(linkInfo, entity.getLinkage(isDefinition),
                             isDefinition, weakImported, isKnownLocal);

lib/SIL/IR/SILFunction.cpp

@@ -178,6 +178,7 @@ void SILFunction::init(SILLinkage Linkage, StringRef Name,
   this->Zombie = false;
   this->HasOwnership = true,
   this->WasDeserializedCanonical = false;
+  this->IsStaticallyLinked = false;
   this->IsWithoutActuallyEscapingThunk = false;
   this->OptMode = unsigned(OptimizationMode::NotSet);
   this->EffectsKindAttr = unsigned(E);

lib/Serialization/DeserializeSIL.cpp

@@ -613,6 +613,10 @@ SILDeserializer::readSILFunctionChecked(DeclID FID, SILFunction *existingFn,
     if (getFile()->getParentModule() == SILMod.getSwiftModule())
       fn->setLinkage(linkage);
 
+    if (getFile()->getParentModule()->isStaticLibrary() ||
+        getFile()->getParentModule() == SILMod.getSwiftModule())
+      fn->setIsStaticallyLinked(true);
+
     // Don't override the transparency or linkage of a function with
     // an existing declaration, except if we deserialized a
     // PublicNonABI function, which has HiddenExternal when