IRGen,Serialization: account for transitive dynamic linkage

When building complex projects, there may cases of static libraries
which expose `@inlinable` functions which reference functions from
dynamically linked dependencies. In such a case, we need to consider the
provenance of the `function_ref` when determining the DLL storage for
linkage. We would previously use the deserialised metadata on the
`SILFunction` as there are entities where the `DeclContext` may not be
deserialised. However, this leaves us in a state where we are unable to
determine the actual provenance correctly in some cases. By simply
accessing the parent module directly from the `SILFunction` we ensure
that we properly identify the origin of the function allowing us to
query the DLL storage property. This further allows us to remove the
extra storage required for whether the `SILFunction` is statically
linked.

Author: compnerd

include/swift/SIL/SILFunction.h

@@ -424,9 +424,6 @@ class SILFunction
   /// The function's effects attribute.
   unsigned EffectsKindAttr : NumEffectsKindBits;
 
-  /// The function is in a statically linked module.
-  unsigned IsStaticallyLinked : 1;
-
   /// If true, the function has lexical lifetimes even if the module does not.
   unsigned ForceEnableLexicalLifetimes : 1;
 
@@ -698,12 +695,6 @@ class SILFunction
     WasDeserializedCanonical = val;
   }
 
-  bool isStaticallyLinked() const { return IsStaticallyLinked; }
-
-  void setIsStaticallyLinked(bool value) {
-    IsStaticallyLinked = value;
-  }
-
   ForceEnableLexicalLifetimes_t forceEnableLexicalLifetimes() const {
     return ForceEnableLexicalLifetimes_t(ForceEnableLexicalLifetimes);
   }

lib/IRGen/GenDecl.cpp

@@ -2404,7 +2404,8 @@ LinkInfo LinkInfo::get(const UniversalLinkageInfo &linkInfo,
     // 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();
+    if (const auto *MD = entity.getSILFunction()->getParentModule())
+      isKnownLocal = MD == swiftModule || MD->isStaticLibrary();
   }
 
   bool weakImported = entity.isWeakImported(swiftModule);

lib/SIL/IR/SILFunction.cpp

@@ -214,7 +214,6 @@ void SILFunction::init(
   this->Zombie = false;
   this->HasOwnership = true,
   this->WasDeserializedCanonical = false;
-  this->IsStaticallyLinked = false;
   this->IsWithoutActuallyEscapingThunk = false;
   this->OptMode = unsigned(OptimizationMode::NotSet);
   this->perfConstraints = PerformanceConstraints::None;
@@ -290,7 +289,6 @@ void SILFunction::createSnapshot(int id) {
   newSnapshot->HasOwnership = HasOwnership;
   newSnapshot->IsWithoutActuallyEscapingThunk = IsWithoutActuallyEscapingThunk;
   newSnapshot->OptMode = OptMode;
-  newSnapshot->IsStaticallyLinked = IsStaticallyLinked;
   newSnapshot->copyEffects(this);
 
   SILFunctionCloner cloner(newSnapshot);

lib/Serialization/DeserializeSIL.cpp

@@ -639,10 +639,6 @@ 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
@@ -678,7 +674,6 @@ SILDeserializer::readSILFunctionChecked(DeclID FID, SILFunction *existingFn,
     fn->setIsAlwaysWeakImported(isWeakImported);
     fn->setClassSubclassScope(SubclassScope(subclassScope));
     fn->setHasCReferences(bool(hasCReferences));
-    fn->setIsStaticallyLinked(MF->getAssociatedModule()->isStaticLibrary());
 
     llvm::VersionTuple available;
     DECODE_VER_TUPLE(available);

test/IRGen/windows-transitive-static-linking.swift

@@ -0,0 +1,23 @@
+// RUN: %empty-directory(%t)
+// RUN: split-file --leading-lines %s %t
+
+// REQUIRES: OS=windows-msvc
+
+// RUN: %target-swiftc_driver -emit-module -emit-module-path %t/swift/dynamic.swiftmodule -I %t/swift %t/dynamic.swift
+// RUN: %target-swiftc_driver -static -emit-module -emit-module-path %t/swift/static.swiftmodule -I %t/swift %t/static.swift
+// RUN: %target-swiftc_driver -O -emit-ir -I %t/swift %t/library.swift | %FileCheck %s
+
+// CHECK: declare dllimport swiftcc i{{[0-9]+}} @"$s7dynamic1fSiyF"()
+
+//--- dynamic.swift
+public func f() -> Int { 32 }
+
+//--- static.swift
+import dynamic
+
+@inlinable
+public func g() -> Int { f() + 1 }
+
+//--- library.swift
+import `static`
+public func h() -> Int { g() + 1 }