IRGen: get metadata symbol of class __StaticArrayStorage the correct way

Fixes an unresolved symbol error when building the stdlib on some platforms.

rdar://119991570

Author: eeckstein

lib/IRGen/GenConstant.cpp

@@ -27,6 +27,8 @@
 #include "StructLayout.h"
 #include "Callee.h"
 #include "ConstantBuilder.h"
+#include "DebugTypeInfo.h"
+#include "swift/IRGen/Linking.h"
 #include "swift/Basic/Range.h"
 #include "swift/SIL/SILModule.h"
 #include "llvm/Support/BLAKE3.h"
@@ -438,11 +440,12 @@ llvm::Constant *irgen::emitConstantObject(IRGenModule &IGM, ObjectInst *OI,
       IGM.swiftImmortalRefCount = var;
     }
     if (!IGM.swiftStaticArrayMetadata) {
-      // type metadata for class __StaticArrayStorage
-      auto *var = new llvm::GlobalVariable(IGM.Module, IGM.TypeMetadataStructTy,
-                                        /*constant*/ true, llvm::GlobalValue::ExternalLinkage,
-                                        /*initializer*/ nullptr, "$ss20__StaticArrayStorageCN");
-      IGM.swiftStaticArrayMetadata = var;
+      auto *classDecl = IGM.getStaticArrayStorageDecl();
+      assert(classDecl && "no __StaticArrayStorage in stdlib");
+      CanType classTy = CanType(ClassType::get(classDecl, Type(), IGM.Context));
+      LinkEntity entity = LinkEntity::forTypeMetadata(classTy, TypeMetadataAddress::AddressPoint);
+      auto *metatype = IGM.getAddrOfLLVMVariable(entity, NotForDefinition, DebugTypeInfo());
+      IGM.swiftStaticArrayMetadata = cast<llvm::GlobalVariable>(metatype);
     }
     elements[0].add(llvm::ConstantStruct::get(ObjectHeaderTy, {
       IGM.swiftStaticArrayMetadata,

lib/IRGen/IRGenModule.cpp

@@ -2046,8 +2046,23 @@ bool IRGenModule::canMakeStaticObjectsReadOnly() {
   if (!Triple.isOSDarwin())
     return false;
 
-  return getAvailabilityContext().isContainedIn(
-          Context.getStaticReadOnlyArraysAvailability());
+  if (!getAvailabilityContext().isContainedIn(Context.getStaticReadOnlyArraysAvailability()))
+    return false;
+
+  if (!getStaticArrayStorageDecl())
+    return false;
+
+  return true;
+}
+
+ClassDecl *IRGenModule::getStaticArrayStorageDecl() {
+  SmallVector<ValueDecl *, 1> results;
+  Context.lookupInSwiftModule("__StaticArrayStorage", results);
+
+  if (results.size() != 1)
+    return nullptr;
+
+  return dyn_cast<ClassDecl>(results[0]);
 }
 
 void IRGenerator::addGenModule(SourceFile *SF, IRGenModule *IGM) {

lib/IRGen/IRGenModule.h

@@ -927,6 +927,8 @@ class IRGenModule {
 
   bool canMakeStaticObjectsReadOnly();
 
+  ClassDecl *getStaticArrayStorageDecl();
+
   bool canUseObjCSymbolicReferences();
 
   Size getAtomicBoolSize() const { return AtomicBoolSize; }