IRGen: Outlined value functions of types that might expand differently in different TUs must use private linkage

lib/IRGen/GenDecl.cpp

@@ -6192,13 +6192,18 @@ IRGenModule::getAddrOfContinuationPrototype(CanSILFunctionType fnType) {
 /// Should we be defining the given helper function?
 static llvm::Function *shouldDefineHelper(IRGenModule &IGM,
                                           llvm::Constant *fn,
-                                          bool setIsNoInline) {
+                                          bool setIsNoInline,
+                                          IRLinkage *linkage) {
   auto *def = dyn_cast<llvm::Function>(fn);
   if (!def) return nullptr;
   if (!def->empty()) return nullptr;
 
   def->setAttributes(IGM.constructInitialAttributes());
-  ApplyIRLinkage(IRLinkage::InternalLinkOnceODR).to(def);
+  if (!linkage)
+    ApplyIRLinkage(IRLinkage::InternalLinkOnceODR).to(def);
+  else
+    ApplyIRLinkage(*linkage).to(def);
+
   def->setDoesNotThrow();
   def->setCallingConv(IGM.DefaultCC);
   if (setIsNoInline)
@@ -6220,15 +6225,17 @@ IRGenModule::getOrCreateHelperFunction(StringRef fnName, llvm::Type *resultTy,
                         llvm::function_ref<void(IRGenFunction &IGF)> generate,
                         bool setIsNoInline,
                         bool forPrologue,
-                        bool isPerformanceConstraint) {
+                        bool isPerformanceConstraint,
+                        IRLinkage *optionalLinkageOverride) {
   llvm::FunctionType *fnTy =
     llvm::FunctionType::get(resultTy, paramTys, false);
 
   llvm::Constant *fn =
       cast<llvm::Constant>(
           Module.getOrInsertFunction(fnName, fnTy).getCallee());
 
-  if (llvm::Function *def = shouldDefineHelper(*this, fn, setIsNoInline)) {
+  if (llvm::Function *def = shouldDefineHelper(*this, fn, setIsNoInline,
+                                               optionalLinkageOverride)) {
     IRGenFunction IGF(*this, def, isPerformanceConstraint);
     if (DebugInfo && !forPrologue)
       DebugInfo->emitArtificialFunction(IGF, def);

lib/IRGen/IRGenModule.h

@@ -147,6 +147,7 @@ namespace irgen {
   class StructLayout;
   class IRGenDebugInfo;
   class IRGenFunction;
+  struct IRLinkage;
   class LinkEntity;
   class LoadableTypeInfo;
   class MetadataLayout;
@@ -1221,7 +1222,8 @@ class IRGenModule {
                         llvm::function_ref<void(IRGenFunction &IGF)> generate,
                         bool setIsNoInline = false,
                         bool forPrologue = false,
-                        bool isPerformanceConstraint = false);
+                        bool isPerformanceConstraint = false,
+                        IRLinkage *optionalLinkage = nullptr);
 
   llvm::Constant *getOrCreateRetainFunction(const TypeInfo &objectTI, SILType t,
                               llvm::Type *llvmType, Atomicity atomicity);

lib/IRGen/Outlining.cpp

@@ -30,6 +30,7 @@
 #include "swift/AST/IRGenOptions.h"
 #include "swift/Basic/Assertions.h"
 #include "swift/IRGen/GenericRequirement.h"
+#include "swift/IRGen/Linking.h"
 #include "swift/SIL/SILModule.h"
 
 using namespace swift;
@@ -489,6 +490,22 @@ llvm::Constant *IRGenModule::getOrCreateOutlinedCopyAddrHelperFunction(
   paramTys.push_back(ptrTy);
   collector.addPolymorphicParameterTypes(paramTys);
 
+  IRLinkage *linkage = nullptr;
+  IRLinkage privateLinkage = {
+    llvm::GlobalValue::PrivateLinkage,
+    llvm::GlobalValue::DefaultVisibility,
+    llvm::GlobalValue::DefaultStorageClass,
+  };
+  auto &TL =
+    getSILModule().Types.getTypeLowering(T, TypeExpansionContext::minimal());
+  // Opaque result types might lead to different expansions in different files.
+  // The default hidden linkonce_odr might lead to linking an implementation
+  // from another file that head a different expansion/different
+  // signature/different implementation.
+  if (TL.getRecursiveProperties().isTypeExpansionSensitive()) {
+    linkage = &privateLinkage;
+  }
+
   return getOrCreateHelperFunction(funcName, ptrTy, paramTys,
       [&](IRGenFunction &IGF) {
         auto params = IGF.collectParameters();
@@ -500,7 +517,8 @@ llvm::Constant *IRGenModule::getOrCreateOutlinedCopyAddrHelperFunction(
       },
       true /*setIsNoInline*/,
       false /*forPrologue*/,
-      collector.IGF.isPerformanceConstraint);
+      collector.IGF.isPerformanceConstraint,
+      linkage);
 }
 
 void TypeInfo::callOutlinedDestroy(IRGenFunction &IGF,
@@ -544,6 +562,22 @@ llvm::Constant *IRGenModule::getOrCreateOutlinedDestroyFunction(
   auto funcName = mangler.mangleOutlinedDestroyFunction(manglingBits.first,
                      manglingBits.second, collector.IGF.isPerformanceConstraint);
 
+  IRLinkage *linkage = nullptr;
+  IRLinkage privateLinkage = {
+    llvm::GlobalValue::PrivateLinkage,
+    llvm::GlobalValue::DefaultVisibility,
+    llvm::GlobalValue::DefaultStorageClass,
+  };
+  auto &TL =
+    getSILModule().Types.getTypeLowering(T, TypeExpansionContext::minimal());
+  // Opaque result types might lead to different expansions in different files.
+  // The default hidden linkonce_odr might lead to linking an implementation
+  // from another file that head a different expansion/different
+  // signature/different implementation.
+  if (TL.getRecursiveProperties().isTypeExpansionSensitive()) {
+    linkage = &privateLinkage;
+  }
+
   auto ptrTy = ti.getStorageType()->getPointerTo();
   llvm::SmallVector<llvm::Type *, 4> paramTys;
   paramTys.push_back(ptrTy);
@@ -565,7 +599,8 @@ llvm::Constant *IRGenModule::getOrCreateOutlinedDestroyFunction(
       },
       true /*setIsNoInline*/,
       false /*forPrologue*/,
-      collector.IGF.isPerformanceConstraint);
+      collector.IGF.isPerformanceConstraint,
+      linkage);
 }
 
 llvm::Constant *IRGenModule::getOrCreateRetainFunction(const TypeInfo &ti,

test/IRGen/Inputs/opaque_result_type_linkage_2.swift

@@ -0,0 +1,4 @@
+public func f<T>(_: T) {
+  var g = G<T>()
+  print(g.lazyVar)
+}

test/IRGen/opaque_result_type_linkage.swift

@@ -0,0 +1,22 @@
+// RUN: %target-swift-frontend -Xllvm -type-lowering-disable-verification -emit-ir -primary-file %s %S/Inputs/opaque_result_type_linkage_2.swift -module-name lib | %FileCheck %s
+// RUN: %target-swift-frontend -Xllvm -type-lowering-disable-verification -emit-ir %s -primary-file %S/Inputs/opaque_result_type_linkage_2.swift -module-name lib | %FileCheck %s --check-prefix=OTHER
+
+protocol P {
+  associatedtype A
+  var a: A { get }
+}
+
+struct G<T>: P {
+  lazy var lazyVar: A = a
+
+  var a: some Any {
+    "hello"
+  }
+}
+
+// We lower the two outlined destroy functions differently depending on the type
+// expansion context (there is an opaque result type).
+// We therefore must not use hidden linkonce_odr linkage.
+
+// CHECK: define{{.*}} private ptr @"$s3lib1GVyxGlWOh"(ptr %0)
+// OTHER: define{{.*}} private ptr @"$s3lib1GVyxGlWOh"(ptr %0, ptr %"some Any", ptr %"Optional<some Any>", ptr %"G<T>")