[Debug Info] Prevent infinite recursion when emitting debug info

for recursive classes. This is achieved by treating types created with
DebugTypeInfo::createFrowardDecl() as unconditional forward
declarations when emitting debug info instead of applying a heuristic
to determine this.

rdar://146688269

Author: adrian-prantl

lib/IRGen/DebugTypeInfo.cpp

@@ -101,6 +101,7 @@ DebugTypeInfo DebugTypeInfo::getTypeMetadata(swift::Type Ty, Size size,
 
 DebugTypeInfo DebugTypeInfo::getForwardDecl(swift::Type Ty) {
   DebugTypeInfo DbgTy(Ty.getPointer());
+  DbgTy.IsForwardDecl = true;
   return DbgTy;
 }
 
@@ -182,6 +183,8 @@ TypeDecl *DebugTypeInfo::getDecl() const {
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 LLVM_DUMP_METHOD void DebugTypeInfo::dump() const {
   llvm::errs() << "[";
+  if (isForwardDecl())
+    llvm::errs() << "forward ";
   llvm::errs() << "Alignment " << Align.getValue() << "] ";
   if (auto *Type = getType())
     Type->dump(llvm::errs());

lib/IRGen/DebugTypeInfo.h

@@ -48,6 +48,7 @@ class DebugTypeInfo {
   bool DefaultAlignment = true;
   bool IsMetadataType = false;
   bool IsFixedBuffer = false;
+  bool IsForwardDecl = false;
 
 public:
   DebugTypeInfo() = default;
@@ -100,6 +101,7 @@ class DebugTypeInfo {
   bool isMetadataType() const { return IsMetadataType; }
   bool hasDefaultAlignment() const { return DefaultAlignment; }
   bool isFixedBuffer() const { return IsFixedBuffer; }
+  bool isForwardDecl() const { return IsForwardDecl; }
   std::optional<uint32_t> getNumExtraInhabitants() const {
     return NumExtraInhabitants;
   }

lib/IRGen/IRGenDebugInfo.cpp

@@ -1326,11 +1326,19 @@ class IRGenDebugInfoImpl : public IRGenDebugInfo {
       }
     }
 
+    // Recursive types such as `class A<B> { let a : A<A> }` would produce an
+    // infinite chain of expansions for the type of `a`. Break these cycles by
+    // emitting any bound generics that still have type parameters as forward
+    // declarations.
+    if (Type->hasTypeParameter() || Type->hasPrimaryArchetype())
+      return createOpaqueStructWithSizedContainer(
+          Scope, Decl ? Decl->getNameStr() : "", File, Line, SizeInBits,
+          AlignInBits, Flags, MangledName, collectGenericParams(Type, true),
+          UnsubstitutedDITy);
+
     // Create the substituted type.
-    auto *OpaqueType =
-        createStructType(Type, Decl, Scope, File, Line, SizeInBits, AlignInBits,
-                         Flags, MangledName, UnsubstitutedDITy);
-    return OpaqueType;
+    return createStructType(Type, Decl, Scope, File, Line, SizeInBits,
+                            AlignInBits, Flags, MangledName, UnsubstitutedDITy);
   }
 
   /// Create debug information for an enum with a raw type (enum E : Int {}).
@@ -1511,9 +1519,9 @@ class IRGenDebugInfoImpl : public IRGenDebugInfo {
   }
 
   llvm::DIType *getOrCreateDesugaredType(Type Ty, DebugTypeInfo DbgTy) {
-    DebugTypeInfo BlandDbgTy(Ty, DbgTy.getAlignment(),
-                             DbgTy.hasDefaultAlignment(),
-                             DbgTy.isMetadataType(), DbgTy.isFixedBuffer());
+    DebugTypeInfo BlandDbgTy(
+        Ty, DbgTy.getAlignment(), DbgTy.hasDefaultAlignment(), false,
+        DbgTy.isFixedBuffer(), DbgTy.getNumExtraInhabitants());
     return getOrCreateType(BlandDbgTy);
   }
 
@@ -1525,8 +1533,8 @@ class IRGenDebugInfoImpl : public IRGenDebugInfo {
   /// Collect the type parameters of a bound generic type. This is needed to
   /// anchor any typedefs that may appear in parameters so they can be
   /// resolved in the debugger without needing to query the Swift module.
-  llvm::DINodeArray
-  collectGenericParams(NominalOrBoundGenericNominalType *BGT, bool AsForwardDeclarations = false) {
+  llvm::DINodeArray collectGenericParams(NominalOrBoundGenericNominalType *BGT,
+                                         bool AsForwardDeclarations = false) {
 
     // Collect the generic args from the type and its parent.
     std::vector<Type> GenericArgs;
@@ -2164,7 +2172,8 @@ class IRGenDebugInfoImpl : public IRGenDebugInfo {
       unsigned FwdDeclLine = 0;
 
       if (Opts.DebugInfoLevel > IRGenDebugInfoLevel::ASTTypes) {
-        if (EnumTy->isSpecialized())
+        if (EnumTy->isSpecialized() && !EnumTy->hasTypeParameter() &&
+            !EnumTy->hasPrimaryArchetype())
           return createSpecializedEnumType(EnumTy, Decl, MangledName,
                                            SizeInBits, AlignInBits, Scope, File,
                                            FwdDeclLine, Flags);
@@ -2561,7 +2570,7 @@ class IRGenDebugInfoImpl : public IRGenDebugInfo {
         if (DbgTy.getType()->getKind() != swift::TypeKind::TypeAlias) {
           // A type with the same canonical type already exists, emit a typedef.
           // This extra step is necessary to break out of loops: We don't
-          // canoncialize types before mangling to preserver sugared types. But
+          // canoncialize types before mangling to preserve sugared types. But
           // some types can also have different equivalent non-canonical
           // representations with no sugar involved, for example a type
           // recursively that appears iniside itself. To deal with the latter we
@@ -2577,6 +2586,19 @@ class IRGenDebugInfoImpl : public IRGenDebugInfo {
           UID = llvm::MDString::get(IGM.getLLVMContext(), Mangled.Sugared);
         }
         // Fall through and create the sugared type.
+      } else if (auto *AliasTy =
+                     llvm::dyn_cast<TypeAliasType>(DbgTy.getType())) {
+        // An alias type, but the mangler failed to produce a sugared type, just
+        // return the desugared type.
+        llvm::DIType *Desugared =
+            getOrCreateDesugaredType(AliasTy->getSinglyDesugaredType(), DbgTy);
+        StringRef Name;
+        if (auto *AliasDecl = AliasTy->getDecl())
+          Name = AliasDecl->getName().str();
+        if (!Name.empty())
+          return DBuilder.createTypedef(Desugared, Name, MainFile, 0,
+                                        updateScope(Scope, DbgTy));
+        return Desugared;
       } else if (llvm::Metadata *CachedTy = DIRefMap.lookup(UID)) {
         auto *DITy = cast<llvm::DIType>(CachedTy);
         assert(sanityCheckCachedType(DbgTy, DITy));
@@ -2594,13 +2616,14 @@ class IRGenDebugInfoImpl : public IRGenDebugInfo {
     // If this is a forward decl, create one for this mangled name and don't
     // cache it.
     if (!isa<PrimaryArchetypeType>(DbgTy.getType()) &&
-        (DbgTy.isFixedBuffer() || !completeType(DbgTy))) {
+        !isa<TypeAliasType>(DbgTy.getType()) &&
+        (DbgTy.isForwardDecl() || DbgTy.isFixedBuffer() ||
+         !completeType(DbgTy))) {
       // In LTO type uniquing is performed based on the UID. Forward
       // declarations may not have a unique ID to avoid a forward declaration
       // winning over a full definition.
       auto *FwdDecl = DBuilder.createReplaceableCompositeType(
           llvm::dwarf::DW_TAG_structure_type, MangledName, Scope, 0, 0,
-
           llvm::dwarf::DW_LANG_Swift);
       FwdDeclTypes.emplace_back(
           std::piecewise_construct, std::make_tuple(MangledName),

test/DebugInfo/BoundGenericStruct.swift

@@ -10,13 +10,13 @@ public let s = S<Int>(t: 0)
 // CHECK-SAME:             templateParams: ![[PARAMS:[0-9]+]]
 // CHECK: ![[PARAMS]] = !{![[INTPARAM:[0-9]+]]}
 // CHECK: ![[INTPARAM]] = !DITemplateTypeParameter(type: ![[INT:[0-9]+]])
-// CHECK: ![[INT]] = !DICompositeType(tag: DW_TAG_structure_type, {{.*}}identifier: "$sSiD"
+// CHECK: ![[INT]] = !DICompositeType(tag: DW_TAG_structure_type, {{.*}}"$sSiD"
 
 // DWARF-DAG: !DICompositeType(tag: DW_TAG_structure_type, {{.*}}templateParams: ![[PARAMS:[0-9]+]]{{.*}}identifier: "$s18BoundGenericStruct1SVySiGD"{{.*}}specification:
 
 // DWARF-DAG: ![[PARAMS]] = !{![[INTPARAM:[0-9]+]]}
 // DWARF-DAG: ![[INTPARAM]] = !DITemplateTypeParameter(type: ![[INT:[0-9]+]])
-// DWARF-DAG: ![[INT]] = !DICompositeType(tag: DW_TAG_structure_type, name: "Int", {{.*}}identifier: "$sSiD"
+// DWARF-DAG: ![[INT]] = !DICompositeType(tag: DW_TAG_structure_type, name: "Int", {{.*}}"$sSiD"
 
 // DWARF-DAG: !DICompositeType(tag: DW_TAG_structure_type, name: "S", {{.*}}identifier: "$s18BoundGenericStruct1SVyxGD")
 // DWARF-DAG: !DIDerivedType(tag: DW_TAG_member, name: "t"

test/DebugInfo/fnptr.swift

@@ -27,8 +27,8 @@ func main() -> Int64 {
     // CHECK-DAG: ![[BAZPTR]] = !DIDerivedType(tag: DW_TAG_pointer_type,{{.*}} baseType: ![[BAZT:[0-9]+]]
     // CHECK-DAG: ![[BAZT]] = !DISubroutineType(types: ![[BAZARGS:.*]])
     // CHECK-DAG: ![[BAZARGS]] = !{![[INT:.*]], ![[FLOAT:.*]]}
-    // CHECK-DAG: ![[INT]] = {{.*}}identifier: "$ss5Int64VD"
-    // CHECK-DAG: ![[FLOAT]] = {{.*}}identifier: "$sSfD"
+    // CHECK-DAG: ![[INT]] = {{.*}}"$ss5Int64VD"
+    // CHECK-DAG: ![[FLOAT]] = {{.*}}"$sSfD"
     var baz_fnptr = baz
     baz_fnptr(2.89)
 

test/DebugInfo/local_type_originally_defined_in.swift

@@ -7,7 +7,7 @@ import local_type_originally_defined_in_other
 
 public func definedInOtherModule() {
   let s = Sheep()
-  // CHECK-DAG: DICompositeType(tag: DW_TAG_structure_type, name: "Sheep"{{.*}}identifier: "$s4Barn5SheepCD
+  // CHECK-DAG: DICompositeType(tag: DW_TAG_structure_type, {{.*}}"$s4Barn5SheepCD
 }
 public func localTypeAliasTest(horse: Horse) {
   // The local type mangling for 'A' mentions 'Horse', which must
@@ -18,7 +18,7 @@ public func localTypeAliasTest(horse: Horse) {
 
   let info = UnsafeMutablePointer<A>.allocate(capacity: 1)
   _ = info
-  // CHECK-DAG: DIDerivedType(tag: DW_TAG_typedef, name: "$s32local_type_originally_defined_in0A13TypeAliasTest5horsey4Barn5HorseV_tF1AL_aD"
+  // CHECK-DAG: name: "$s32local_type_originally_defined_in0A13TypeAliasTest5horsey4Barn5HorseV_tF1AL_aD"
 }
 
 
@@ -31,7 +31,7 @@ public func localTypeTest(horse: Horse) {
 
   let info = UnsafeMutablePointer<LocalStruct>.allocate(capacity: 1)
   _ = info
-  // CHECK-DAG: DICompositeType(tag: DW_TAG_structure_type, {{.*}}identifier: "$s32local_type_originally_defined_in0A8TypeTest5horsey4Barn5HorseV_tF11LocalStructL_VD"
+  // CHECK-DAG: DICompositeType(tag: DW_TAG_structure_type, {{.*}}: "$s32local_type_originally_defined_in0A8TypeTest5horsey4Barn5HorseV_tF11LocalStructL_VD"
 }
 
 public func localTypeAliasTest() -> Horse {
@@ -40,7 +40,7 @@ public func localTypeAliasTest() -> Horse {
   let info = UnsafeMutablePointer<B>.allocate(capacity: 1)
   _ = info
   return Horse()
-  // CHECK-DAG: DIDerivedType(tag: DW_TAG_typedef, name: "$s32local_type_originally_defined_in0A13TypeAliasTest4Barn5HorseVyF1BL_aD"
+  // CHECK-DAG: name: "$s32local_type_originally_defined_in0A13TypeAliasTest4Barn5HorseVyF1BL_aD"
 }
 
 public func localTypeAliasTestGeneric<T: Cow>(cow: T) {

test/DebugInfo/mangling-stdlib.swift

@@ -1,3 +1,4 @@
 // RUN: %target-swift-frontend -parse-stdlib %s -emit-ir -g -o - | %FileCheck %s
-// CHECK:  !DIDerivedType(tag: DW_TAG_typedef, name: "$sBbD",
+// CHECK:  !DIDerivedType(tag: DW_TAG_typedef, name: "BridgeObject", {{.*}}baseType: ![[BT:[0-9]+]]
+// CHECK: ![[BT]] = {{.*}}"$sBbD"
 var bo : Builtin.BridgeObject

test/DebugInfo/typealias.swift

@@ -2,7 +2,7 @@
 
 func markUsed<T>(_ t: T) {}
 
-// CHECK-DAG: ![[INTTYPE:.*]] = !DICompositeType(tag: DW_TAG_structure_type, name: "Int", {{.*}})
+// CHECK-DAG: ![[INTTYPE:.*]] = !DICompositeType(tag: DW_TAG_structure_type, {{.*}}"$sSiD"
 
 public class DWARF {
 // CHECK-DAG: ![[BASE:.*]] = !DICompositeType({{.*}}identifier: "$ss6UInt32VD"

test/DebugInfo/typealias_indirect.swift

@@ -4,8 +4,8 @@
 //        and we can preserve that MyClass<LocalAlias, Bool> = MyClass<Bool, Bool>
 //        we cannot preserve that LocalAlias = Bool.
 
-// CHECK: !DIDerivedType(tag: DW_TAG_typedef, name: "$s1a7MyClassCyAA10LocalAliasaSbGD",{{.*}}baseType: ![[BOOLBOOLTY:[0-9]+]]
-// CHECK: ![[BOOLBOOLTY]] = !DICompositeType(tag: DW_TAG_structure_type, name: "MyClass", {{.*}}identifier: "$s1a7MyClassCyS2bGD"
+// CHECK: !DIDerivedType(tag: DW_TAG_typedef, name: "$s1a10ClassAliasaD"{{.*}}baseType: ![[LOCAL_BOOLTY:[0-9]+]]
+// CHECK: ![[LOCAL_BOOLTY]] = !DICompositeType(tag: DW_TAG_structure_type, name: "MyClass", {{.*}}identifier: "$s1a7MyClassCyAA10LocalAliasaSbGD"
 
 // FIXME: !DIDerivedType(tag: DW_TAG_typedef, name: "$s1a10LocalAliasaD", {{.*}}baseType: ![[BASETY:[0-9]+]]
 // FIXME: ![[BASETY]]{{.*}}$sSbD

test/DebugInfo/value-generics.swift

@@ -24,5 +24,5 @@ func concreteBA(_: Builtin.FixedArray<4, Int>) {}
 // CHECK-DAG: ![[COUNT_PARAM]] = !DITemplateTypeParameter(type: ![[COUNT_TYPE:.*]])
 // CHECK-DAG: ![[COUNT_TYPE]] = !DICompositeType({{.*}}name: "$s$1_D"
 // CHECK-DAG: ![[ELEMENT_PARAM]] = !DITemplateTypeParameter(type: ![[ELEMENT_TYPE:.*]])
-// CHECK-DAG: ![[ELEMENT_TYPE]] = !DICompositeType({{.*}}identifier: "$sSiD"
+// CHECK-DAG: ![[ELEMENT_TYPE]] = !DICompositeType({{.*}}"$sSiD"
 func concreteV(_: Slab<2, Int>) {}