[IRGen] Correctly assign lazily-emitted global variables in multi-threaded IRGen

include/swift/SIL/SILGlobalVariable.h

@@ -52,9 +52,11 @@ class SILGlobalVariable
   /// The SIL module that the global variable belongs to.
   SILModule &Module;
 
-  /// The module that defines this global variable. This member should only be
-  /// when a global variable is deserialized to be emitted into another module.
-  ModuleDecl *ParentModule = nullptr;
+  /// Either the declaration context of the global variable or the parent
+  /// module in which the global variable resides.
+  ///
+  /// The latter is only used for a deserialized global variable.
+  llvm::PointerUnion<DeclContext *, ModuleDecl *> DeclCtxOrParentModule;
 
   /// The mangled name of the variable, which will be propagated to the
   /// binary.  A pointer into the module's lookup table.
@@ -131,13 +133,21 @@ class SILGlobalVariable
 
   SILModule &getModule() const { return Module; }
 
-  /// Returns the module that defines this function.
+  /// Returns the module that defines this global variable.
   ModuleDecl *getParentModule() const;
 
-  /// Sets \c ParentModule as fallback if \c DeclCtxt is not available to
-  /// provide the parent module.
+  /// Get the declaration context of this global variable, if it has one.
+  DeclContext *getDeclContext() const;
+
+  /// Sets the parent module for a deserialized global variable.
   void setParentModule(ModuleDecl *module) {
-    ParentModule = module;
+    DeclCtxOrParentModule = module;
+  }
+
+  /// Sets the declaration context for a global variable that's not anchored to
+  /// a declaration.
+  void setDeclContext(DeclContext *declCtx) {
+    DeclCtxOrParentModule = declCtx;
   }
 
   SILType getLoweredType() const { return LoweredType; }

lib/IRGen/GenDecl.cpp

@@ -1561,8 +1561,8 @@ void IRGenerator::addLazyGlobalVariable(SILGlobalVariable *v) {
   assert(!FinishedEmittingLazyDefinitions);
   LazyGlobalVariables.push_back(v);
 
-  if (auto decl = v->getDecl()) {
-    if (decl->getDeclContext()->getParentSourceFile())
+  if (auto dc = v->getDeclContext()) {
+    if (dc->getParentSourceFile())
       return;
   }
 

lib/IRGen/IRGenModule.cpp

@@ -2333,9 +2333,8 @@ IRGenModule *IRGenerator::getGenModule(SILGlobalVariable *v) {
   if (found != DefaultIGMForGlobalVariable.end())
     return found->second;
 
-  if (auto decl = v->getDecl()) {
-    return getGenModule(decl->getDeclContext());
-  }
+  if (auto *dc = v->getDeclContext())
+    return getGenModule(dc);
 
   return getPrimaryIGM();
 }

lib/SIL/IR/SILGlobalVariable.cpp

@@ -44,7 +44,23 @@ SILGlobalVariable *SILGlobalVariable::create(SILModule &M, SILLinkage linkage,
 }
 
 ModuleDecl *SILGlobalVariable::getParentModule() const {
-  return ParentModule ? ParentModule : getModule().getSwiftModule();
+  if (auto parentModule = DeclCtxOrParentModule.dyn_cast<ModuleDecl *>())
+    return parentModule;
+
+  if (auto declContext = DeclCtxOrParentModule.dyn_cast<DeclContext *>())
+    return declContext->getParentModule();
+
+  return getModule().getSwiftModule();
+}
+
+DeclContext *SILGlobalVariable::getDeclContext() const {
+  if (auto var = getDecl())
+    return var->getDeclContext();
+
+  if (auto declContext = DeclCtxOrParentModule.dyn_cast<DeclContext *>())
+    return declContext;
+
+  return nullptr;
 }
 
 static bool isGlobalLet(SILModule &mod, VarDecl *decl, SILType type) {

lib/SILGen/SILGenGlobalVariable.cpp

@@ -243,6 +243,7 @@ void SILGenModule::emitGlobalInitialization(PatternBindingDecl *pd,
                                              IsNotSerialized,
                                              onceTokenBuffer, onceSILTy);
   onceToken->setDeclaration(false);
+  onceToken->setDeclContext(pd->getDeclContext());
 
   // Emit the initialization code into a function.
   Mangle::ASTMangler FuncMangler(pd->getASTContext());

test/IRGen/multithread_global_var.swift

@@ -0,0 +1,24 @@
+// RUN: %empty-directory(%t/src)
+// RUN: split-file %s %t/src
+
+// RUN: %target-swift-frontend %t/src/A.swift %t/src/B.swift -emit-ir -o %t/A.ll -o %t/B.ll -num-threads 2 -O -g -module-name test
+// RUN: %FileCheck --check-prefix=CHECK-A %s <%t/A.ll
+// RUN: %FileCheck --check-prefix=CHECK-B %s <%t/B.ll
+
+//--- A.swift
+
+public func f() -> String { "hello" }
+
+public func g() -> Bool {
+  f() == X.introduction
+}
+
+// CHECK-A: @"$s4test1XV12introduction_Wz" = external hidden global
+
+//--- B.swift
+
+public struct X {
+  public static var introduction: String = f().uppercased()
+}
+
+// CHECK-B: @"$s4test1XV12introduction_Wz" = weak_odr hidden global