IRGen: simplify the stdlib special casing for Windows

Remove `IRGenModule::useDllStorage()` as there is a standalone version
that is available and the necessary information is public from the
`IRGenModule` type. Additionally, avoid the wrapped `isStandardLibrary`
preferring to use the same method off of the public accessors. This
works towards removing some of the standard library special casing so
that it is possible to support both static and dynamic standard
libraries on Windows.

Author: compnerd

lib/IRGen/GenValueWitness.cpp

@@ -1396,9 +1396,9 @@ getAddrOfKnownValueWitnessTable(IRGenModule &IGM, CanType type,
                                 bool relativeReference) {
   // Native PE binaries shouldn't reference data symbols across DLLs, so disable
   // this on Windows, unless we're forming a relative indirectable reference.
-  if (IGM.useDllStorage() && !relativeReference)
+  if (useDllStorage(IGM.Triple) && !relativeReference)
     return {};
-  
+
   if (auto nom = type->getAnyNominal()) {
     // TODO: Non-C enums have extra inhabitants and also need additional value
     // witnesses for their tag manipulation (except when they're empty, in

lib/IRGen/IRGenModule.cpp

@@ -1057,10 +1057,6 @@ bool isStandardLibrary(const llvm::Module &M) {
 }
 }
 
-bool IRGenModule::isStandardLibrary() const {
-  return ::isStandardLibrary(Module);
-}
-
 llvm::FunctionType *swift::getRuntimeFnType(llvm::Module &Module,
                                            llvm::ArrayRef<llvm::Type*> retTypes,
                                            llvm::ArrayRef<llvm::Type*> argTypes) {
@@ -1293,7 +1289,7 @@ IRGenModule::createStringConstant(StringRef Str, bool willBeRelativelyAddressed,
     if (NAME)                                                                  \
       return NAME;                                                             \
     NAME = Module.getOrInsertGlobal(SYM, FullExistentialTypeMetadataStructTy); \
-    if (useDllStorage() && !isStandardLibrary())                               \
+    if (!getSwiftModule()->isStdlibModule())                                   \
       ApplyIRLinkage(IRLinkage::ExternalImport)                                \
           .to(cast<llvm::GlobalVariable>(NAME));                               \
     return NAME;                                                               \
@@ -2127,8 +2123,6 @@ void IRGenModule::error(SourceLoc loc, const Twine &message) {
                          message.toStringRef(buffer));
 }
 
-bool IRGenModule::useDllStorage() { return ::useDllStorage(Triple); }
-
 // In embedded swift features are available independent of deployment and
 // runtime targets because the runtime library is always statically linked
 // to the program.
@@ -2152,9 +2146,9 @@ bool IRGenModule::shouldPrespecializeGenericMetadata() {
   auto canPrespecializeTarget =
       (Triple.isOSDarwin() || Triple.isOSWindows() ||
        (Triple.isOSLinux() && !(Triple.isARM() && Triple.isArch32Bit())));
-  if (canPrespecializeTarget && isStandardLibrary()) {
+  if (canPrespecializeTarget && getSwiftModule()->isStdlibModule())
     return IRGen.Opts.PrespecializeGenericMetadata;
-  }
+
   auto &context = getSwiftModule()->getASTContext();
   auto deploymentAvailability = AvailabilityRange::forDeploymentTarget(context);
   return IRGen.Opts.PrespecializeGenericMetadata &&

lib/IRGen/IRGenModule.h

@@ -968,8 +968,6 @@ class IRGenModule {
   void fatal_unimplemented(SourceLoc, StringRef Message);
   void error(SourceLoc loc, const Twine &message);
 
-  bool useDllStorage();
-
   bool shouldPrespecializeGenericMetadata();
 
   bool canMakeStaticObjectReadOnly(SILType objectType);
@@ -1510,7 +1508,6 @@ class IRGenModule {
   llvm::Module *getModule() const;
   llvm::AttributeList getAllocAttrs();
   llvm::Constant *getDeletedAsyncMethodErrorAsyncFunctionPointer();
-  bool isStandardLibrary() const;
 
 private:
   llvm::Constant *EmptyTupleMetadata = nullptr;

lib/IRGen/MetadataRequest.cpp

@@ -602,7 +602,7 @@ irgen::tryEmitConstantHeapMetadataRef(IRGenModule &IGM,
 ConstantReference
 irgen::tryEmitConstantTypeMetadataRef(IRGenModule &IGM, CanType type,
                                       SymbolReferenceKind refKind) {
-  if (IGM.isStandardLibrary())
+  if (IGM.getSwiftModule()->isStdlibModule())
     return ConstantReference();
   if (isCanonicalCompleteTypeMetadataStaticallyAddressable(IGM, type))
     return ConstantReference();