[IRGen] When emitting llvm.used.conditional list, strip all pointer casts in dependencies (#40678)

Author: kubamracek

lib/IRGen/GenDecl.cpp

@@ -3766,9 +3766,7 @@ void IRGenModule::appendLLVMUsedConditionalEntry(llvm::GlobalVariable *var,
                             llvm::ConstantAsMetadata::get(dependsOn),
                         }),
   };
-  auto *usedConditional =
-      Module.getOrInsertNamedMetadata("llvm.used.conditional");
-  usedConditional->addOperand(llvm::MDNode::get(Module.getContext(), metadata));
+  UsedConditionals.push_back(llvm::MDNode::get(Module.getContext(), metadata));
 }
 
 /// Expresses that `var` is removable (dead-strippable) when either the protocol
@@ -3795,9 +3793,32 @@ void IRGenModule::appendLLVMUsedConditionalEntry(
                             llvm::ConstantAsMetadata::get(type),
                         }),
   };
+  UsedConditionals.push_back(llvm::MDNode::get(Module.getContext(), metadata));
+}
+
+void IRGenModule::emitUsedConditionals() {
+  if (UsedConditionals.empty())
+    return;
+
   auto *usedConditional =
       Module.getOrInsertNamedMetadata("llvm.used.conditional");
-  usedConditional->addOperand(llvm::MDNode::get(Module.getContext(), metadata));
+
+  for (auto *M : UsedConditionals) {
+    // Process the dependencies ("edges") and strip any pointer casts on them.
+    // Those might appear when a dependency is originally added against a
+    // declaration only, and later the declaration is RAUW'd with a definition
+    // causing a bitcast to get added to the metadata entry in the dependency.
+    auto *DependenciesMD =
+        dyn_cast_or_null<llvm::MDNode>(M->getOperand(2).get());
+    for (unsigned int I = 0; I < DependenciesMD->getNumOperands(); I++) {
+      auto *Dependency = DependenciesMD->getOperand(I).get();
+      auto *C = llvm::mdconst::extract_or_null<llvm::Constant>(Dependency)
+                    ->stripPointerCasts();
+      DependenciesMD->replaceOperandWith(I, llvm::ConstantAsMetadata::get(C));
+    }
+
+    usedConditional->addOperand(M);
+  }
 }
 
 /// Emit the protocol descriptors list and return it (if asContiguousArray is

lib/IRGen/IRGenModule.cpp

@@ -1690,6 +1690,7 @@ bool IRGenModule::finalize() {
   emitSwiftAsyncExtendedFrameInfoWeakRef();
   emitAutolinkInfo();
   emitGlobalLists();
+  emitUsedConditionals();
   if (DebugInfo)
     DebugInfo->finalize();
   cleanupClangCodeGenMetadata();

lib/IRGen/IRGenModule.h

@@ -1217,6 +1217,9 @@ class IRGenModule {
   void emitLazyObjCProtocolDefinitions();
   void emitLazyObjCProtocolDefinition(ProtocolDecl *proto);
 
+  llvm::SmallVector<llvm::MDNode *> UsedConditionals;
+  void emitUsedConditionals();
+
   void emitGlobalLists();
   void emitAutolinkInfo();
   void cleanupClangCodeGenMetadata();

test/IRGen/conditional-dead-strip-ir.swift

@@ -27,19 +27,19 @@ public enum Enum {
 // CHECK:      !llvm.used.conditional = !{[[M1:!.*]], [[M2:!.*]], [[M3:!.*]], [[M4:!.*]], [[C1:!.*]], [[C2:!.*]], [[C3:!.*]], [[C4:!.*]], [[C5:!.*]]}
 
 // CHECK-DAG:      [[M1]]  = !{{{.*}} @"$s4main11TheProtocol_pMF", i32 0, [[M1A:!.*]]}
-// CHECK-DAG:      [[M1A]] = !{{{.*}} @"$s4main11TheProtocolMp"
+// CHECK-DAG:      [[M1A]] =   {{.*}} @"$s4main11TheProtocolMp"
 // CHECK-DAG:      [[M2]]  = !{{{.*}} @"$s4main5ClassCMF", i32 0, [[M2A:!.*]]}
-// CHECK-DAG:      [[M2A]] = !{{{.*}} @"$s4main5ClassCMn"
+// CHECK-DAG:      [[M2A]] =   {{.*}} @"$s4main5ClassCMn"
 // CHECK-DAG:      [[M3]]  = !{{{.*}} @"$s4main6StructVMF", i32 0, [[M3A:!.*]]}
-// CHECK-DAG:      [[M3A]] = !{{{.*}} @"$s4main6StructVMn"
+// CHECK-DAG:      [[M3A]] =   {{.*}} @"$s4main6StructVMn"
 // CHECK-DAG:      [[M4]]  = !{{{.*}} @"$s4main4EnumOMF", i32 0, [[M4A:!.*]]}
-// CHECK-DAG:      [[M4A]] = !{{{.*}} @"$s4main4EnumOMn"
+// CHECK-DAG:      [[M4A]] =   {{.*}} @"$s4main4EnumOMn"
 
 // CHECK-DAG:      [[C1]]  = !{{{.*}} @"$s4main11TheProtocolHr", i32 0, [[C1A:!.*]]}
-// CHECK-DAG:      [[C1A]] = !{{{.*}} @"$s4main11TheProtocolMp"}
+// CHECK-DAG:      [[C1A]] =   {{.*}} @"$s4main11TheProtocolMp"}
 
 // CHECK-DAG:      [[C2]]  = !{{{.*}} @"$s4main5ClassCAA11TheProtocolAAHc", i32 1, [[C2A:!.*]]}
-// CHECK-DAG:      [[C2A]] = !{{{.*}} @"$s4main11TheProtocolMp", {{.*}} @"$s4main5ClassCMn"}
+// CHECK-DAG:      [[C2A]] =   {{.*}} @"$s4main11TheProtocolMp", {{.*}} @"$s4main5ClassCMn"}
 
 // CHECK-DAG:      [[C3]]  = !{{{.*}} @"$s4main5ClassCHn", i32 0, [[M2A:!.*]]}
 

test/IRGen/conditional-dead-strip-reflection.swift

@@ -0,0 +1,31 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-build-swift -Xfrontend -conditional-runtime-records %s -emit-ir -o %t/main.ll
+// RUN: %target-clang %t/main.ll -isysroot %sdk -L%swift_obj_root/lib/swift/%target-sdk-name -flto -o %t/main
+// RUN: %target-swift-reflection-dump -binary-filename %t/main | %FileCheck %s
+
+// FIXME(mracek): More work needed to get this to work on non-Apple platforms.
+// REQUIRES: VENDOR=apple
+
+// For LTO, the linker dlopen()'s the libLTO library, which is a scenario that
+// ASan cannot work in ("Interceptors are not working, AddressSanitizer is
+// loaded too late").
+// REQUIRES: no_asan
+
+public protocol TheProtocol {
+}
+
+public class Class: TheProtocol {
+}
+
+public struct Struct {
+}
+
+public enum Enum {
+}
+
+// CHECK: FIELDS:
+// CHECK: =======
+// CHECK: main.TheProtocol
+// CHECK: main.Class
+// CHECK: main.Struct
+// CHECK: main.Enum