[CIR] Add support for completing forward-declared types (#143176)

This adds the needed handling for completing record types which were
previously declared leading us to create an incomplete record type.

Author: andykaylor

clang/include/clang/CIR/CIRGenerator.h

@@ -78,6 +78,7 @@ class CIRGenerator : public clang::ASTConsumer {
   bool HandleTopLevelDecl(clang::DeclGroupRef group) override;
   void HandleTranslationUnit(clang::ASTContext &astContext) override;
   void HandleInlineFunctionDefinition(clang::FunctionDecl *d) override;
+  void HandleTagDeclDefinition(clang::TagDecl *d) override;
   void CompleteTentativeDefinition(clang::VarDecl *d) override;
 
   mlir::ModuleOp getModule() const;

clang/include/clang/CIR/MissingFeatures.h

@@ -199,7 +199,6 @@ struct MissingFeatures {
   static bool msabi() { return false; }
   static bool typeChecks() { return false; }
   static bool lambdaFieldToName() { return false; }
-  static bool updateCompletedType() { return false; }
   static bool moduleNameHash() { return false; }
   static bool constantFoldSwitchStatement() { return false; }
   static bool cudaSupport() { return false; }

clang/lib/CIR/CodeGen/CIRGenModule.cpp

@@ -838,6 +838,11 @@ void CIRGenModule::maybeSetTrivialComdat(const Decl &d, mlir::Operation *op) {
   assert(!cir::MissingFeatures::opFuncSetComdat());
 }
 
+void CIRGenModule::updateCompletedType(const TagDecl *td) {
+  // Make sure that this type is translated.
+  genTypes.updateCompletedType(td);
+}
+
 // TODO(CIR): this could be a common method between LLVM codegen.
 static bool isVarDeclStrongDefinition(const ASTContext &astContext,
                                       CIRGenModule &cgm, const VarDecl *vd,
@@ -1145,6 +1150,7 @@ void CIRGenModule::emitTopLevelDecl(Decl *decl) {
 
   // No code generation needed.
   case Decl::UsingShadow:
+  case Decl::Empty:
     break;
 
   // C++ Decls

clang/lib/CIR/CodeGen/CIRGenModule.h

@@ -241,6 +241,9 @@ class CIRGenModule : public CIRGenTypeCache {
 
   void emitTentativeDefinition(const VarDecl *d);
 
+  // Make sure that this type is translated.
+  void updateCompletedType(const clang::TagDecl *td);
+
   bool supportsCOMDAT() const;
   void maybeSetTrivialComdat(const clang::Decl &d, mlir::Operation *op);
 

clang/lib/CIR/CodeGen/CIRGenTypes.cpp

@@ -432,8 +432,6 @@ mlir::Type CIRGenTypes::convertType(QualType type) {
   }
 
   case Type::Enum: {
-    // TODO(cir): Implement updateCompletedType for enums.
-    assert(!cir::MissingFeatures::updateCompletedType());
     const EnumDecl *ED = cast<EnumType>(ty)->getDecl();
     if (auto integerType = ED->getIntegerType(); !integerType.isNull())
       return convertType(integerType);
@@ -586,3 +584,40 @@ const CIRGenFunctionInfo &CIRGenTypes::arrangeGlobalDeclaration(GlobalDecl gd) {
 
   return arrangeFunctionDeclaration(fd);
 }
+
+// When we find the full definition for a TagDecl, replace the 'opaque' type we
+// previously made for it if applicable.
+void CIRGenTypes::updateCompletedType(const TagDecl *td) {
+  // If this is an enum being completed, then we flush all non-struct types
+  // from the cache. This allows function types and other things that may be
+  // derived from the enum to be recomputed.
+  if (const auto *ed = dyn_cast<EnumDecl>(td)) {
+    // Classic codegen clears the type cache if it contains an entry for this
+    // enum type that doesn't use i32 as the underlying type, but I can't find
+    // a test case that meets that condition. C++ doesn't allow forward
+    // declaration of enums, and C doesn't allow an incomplete forward
+    // declaration with a non-default type.
+    assert(
+        !typeCache.count(ed->getTypeForDecl()) ||
+        (convertType(ed->getIntegerType()) == typeCache[ed->getTypeForDecl()]));
+    // If necessary, provide the full definition of a type only used with a
+    // declaration so far.
+    assert(!cir::MissingFeatures::generateDebugInfo());
+    return;
+  }
+
+  // If we completed a RecordDecl that we previously used and converted to an
+  // anonymous type, then go ahead and complete it now.
+  const auto *rd = cast<RecordDecl>(td);
+  if (rd->isDependentType())
+    return;
+
+  // Only complete if we converted it already. If we haven't converted it yet,
+  // we'll just do it lazily.
+  if (recordDeclTypes.count(astContext.getTagDeclType(rd).getTypePtr()))
+    convertRecordDeclType(rd);
+
+  // If necessary, provide the full definition of a type only used with a
+  // declaration so far.
+  assert(!cir::MissingFeatures::generateDebugInfo());
+}

clang/lib/CIR/CodeGen/CIRGenTypes.h

@@ -151,6 +151,10 @@ class CIRGenTypes {
 
   const CIRGenFunctionInfo &arrangeGlobalDeclaration(GlobalDecl gd);
 
+  /// UpdateCompletedType - when we find the full definition for a TagDecl,
+  /// replace the 'opaque' type we previously made for it if applicable.
+  void updateCompletedType(const clang::TagDecl *td);
+
   /// Free functions are functions that are compatible with an ordinary C
   /// function pointer type.
   const CIRGenFunctionInfo &

clang/lib/CIR/CodeGen/CIRGenerator.cpp

@@ -129,6 +129,29 @@ void CIRGenerator::emitDeferredDecls() {
   deferredInlineMemberFuncDefs.clear();
 }
 
+/// HandleTagDeclDefinition - This callback is invoked each time a TagDecl to
+/// (e.g. struct, union, enum, class) is completed. This allows the client to
+/// hack on the type, which can occur at any point in the file (because these
+/// can be defined in declspecs).
+void CIRGenerator::HandleTagDeclDefinition(TagDecl *d) {
+  if (diags.hasErrorOccurred())
+    return;
+
+  // Don't allow re-entrant calls to CIRGen triggered by PCH deserialization to
+  // emit deferred decls.
+  HandlingTopLevelDeclRAII handlingDecl(*this, /*EmitDeferred=*/false);
+
+  cgm->updateCompletedType(d);
+
+  // For MSVC compatibility, treat declarations of static data members with
+  // inline initializers as definitions.
+  if (astContext->getTargetInfo().getCXXABI().isMicrosoft())
+    cgm->errorNYI(d->getSourceRange(), "HandleTagDeclDefinition: MSABI");
+  // For OpenMP emit declare reduction functions, if required.
+  if (astContext->getLangOpts().OpenMP)
+    cgm->errorNYI(d->getSourceRange(), "HandleTagDeclDefinition: OpenMP");
+}
+
 void CIRGenerator::CompleteTentativeDefinition(VarDecl *d) {
   if (diags.hasErrorOccurred())
     return;

clang/lib/CIR/FrontendAction/CIRGenAction.cpp

@@ -140,6 +140,13 @@ class CIRGenConsumer : public clang::ASTConsumer {
     }
   }
 
+  void HandleTagDeclDefinition(TagDecl *D) override {
+    PrettyStackTraceDecl CrashInfo(D, SourceLocation(),
+                                   Context->getSourceManager(),
+                                   "CIR generation of declaration");
+    Gen->HandleTagDeclDefinition(D);
+  }
+
   void CompleteTentativeDefinition(VarDecl *D) override {
     Gen->CompleteTentativeDefinition(D);
   }

clang/test/CIR/CodeGen/forward-decls.cpp

@@ -0,0 +1,124 @@
+// RUN: split-file %s %t
+
+
+//--- incomplete_struct
+
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir -emit-cir %t/incomplete_struct -o %t/incomplete_struct.cir
+// RUN: FileCheck %s --input-file=%t/incomplete_struct.cir --check-prefix=CHECK1
+
+// Forward declaration of the record is never defined, so it is created as
+// an incomplete struct in CIR and will remain as such.
+
+// CHECK1: ![[INC_STRUCT:.+]] = !cir.record<struct "IncompleteStruct" incomplete>
+struct IncompleteStruct;
+// CHECK1: testIncompleteStruct(%arg0: !cir.ptr<![[INC_STRUCT]]>
+void testIncompleteStruct(struct IncompleteStruct *s) {};
+
+
+
+//--- mutated_struct
+
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir -emit-cir %t/mutated_struct -o %t/mutated_struct.cir
+// RUN: FileCheck %s --input-file=%t/mutated_struct.cir --check-prefix=CHECK2
+
+// Foward declaration of the struct is followed by usage, then definition.
+// This means it will initially be created as incomplete, then completed.
+
+// CHECK2: ![[COMPLETE:.+]] = !cir.record<struct "ForwardDeclaredStruct" {!s32i}>
+// CHECK2: testForwardDeclaredStruct(%arg0: !cir.ptr<![[COMPLETE]]>
+struct ForwardDeclaredStruct;
+void testForwardDeclaredStruct(struct ForwardDeclaredStruct *fds) {};
+struct ForwardDeclaredStruct {
+  int testVal;
+};
+
+
+
+//--- recursive_struct
+
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir -emit-cir %t/recursive_struct -o %t/recursive_struct.cir
+// RUN: FileCheck --check-prefix=CHECK3 --input-file=%t/recursive_struct.cir %s
+
+// Struct is initially forward declared since the self-reference is generated
+// first. Then, once the type is fully generated, it is completed.
+
+// CHECK3: ![[STRUCT:.+]] = !cir.record<struct "RecursiveStruct" {!s32i, !cir.ptr<!cir.record<struct "RecursiveStruct">>}>
+struct RecursiveStruct {
+  int value;
+  struct RecursiveStruct *next;
+};
+// CHECK3: testRecursiveStruct(%arg0: !cir.ptr<![[STRUCT]]>
+void testRecursiveStruct(struct RecursiveStruct *arg) {
+  // CHECK3: %[[#NEXT:]] = cir.get_member %{{.+}}[1] {name = "next"} : !cir.ptr<![[STRUCT]]> -> !cir.ptr<!cir.ptr<![[STRUCT]]>>
+  // CHECK3: %[[#DEREF:]] = cir.load{{.*}} %[[#NEXT]] : !cir.ptr<!cir.ptr<![[STRUCT]]>>, !cir.ptr<![[STRUCT]]>
+  // CHECK3: cir.get_member %[[#DEREF]][0] {name = "value"} : !cir.ptr<![[STRUCT]]> -> !cir.ptr<!s32i>
+  arg->next->value;
+}
+
+
+
+//--- indirect_recursive_struct
+
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir -emit-cir %t/indirect_recursive_struct -o %t/indirect_recursive_struct.cir
+// RUN: FileCheck --check-prefix=CHECK4 --input-file=%t/indirect_recursive_struct.cir %s
+
+// Node B refers to A, and vice-versa, so a forward declaration is used to
+// ensure the classes can be defined. Since types alias are not yet supported
+// in recursive type, each struct is expanded until there are no more recursive
+// types, or all the recursive types are self references.
+
+// CHECK4: ![[B:.+]] = !cir.record<struct "StructNodeB" {!s32i, !cir.ptr<!cir.record<struct "StructNodeA" {!s32i, !cir.ptr<!cir.record<struct "StructNodeB">>}
+// CHECK4: ![[A:.+]] = !cir.record<struct "StructNodeA" {!s32i, !cir.ptr<![[B]]>}>
+struct StructNodeB;
+struct StructNodeA {
+  int value;
+  struct StructNodeB *next;
+};
+struct StructNodeB {
+  int value;
+  struct StructNodeA *next;
+};
+
+void testIndirectSelfReference(struct StructNodeA arg) {
+  // CHECK4: %[[#V1:]] = cir.get_member %{{.+}}[1] {name = "next"} : !cir.ptr<![[A]]> -> !cir.ptr<!cir.ptr<![[B]]>>
+  // CHECK4: %[[#V2:]] = cir.load{{.*}} %[[#V1]] : !cir.ptr<!cir.ptr<![[B]]>>, !cir.ptr<![[B]]>
+  // CHECK4: %[[#V3:]] = cir.get_member %[[#V2]][1] {name = "next"} : !cir.ptr<![[B]]> -> !cir.ptr<!cir.ptr<![[A]]>>
+  // CHECK4: %[[#V4:]] = cir.load{{.*}} %[[#V3]] : !cir.ptr<!cir.ptr<![[A]]>>, !cir.ptr<![[A]]>
+  // CHECK4: cir.get_member %[[#V4]][0] {name = "value"} : !cir.ptr<![[A]]> -> !cir.ptr<!s32i>
+  arg.next->next->value;
+}
+
+
+
+//--- complex_struct
+
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir -emit-cir %t/complex_struct -o %t/complex_struct.cir
+// RUN: FileCheck --check-prefix=CHECK5 --input-file=%t/complex_struct.cir %s
+
+// A sizeable complex struct just to double check that stuff is working.
+// CHECK5: !cir.record<struct "anon.0" {!cir.ptr<!cir.record<struct "A" {!cir.record<struct "anon.0">, !cir.record<struct "B" {!cir.ptr<!cir.record<struct "B">>, !cir.record<struct "C" {!cir.ptr<!cir.record<struct "A">>, !cir.ptr<!cir.record<struct "B">>, !cir.ptr<!cir.record<struct "C">>}>, !cir.record<union "anon.1" {!cir.ptr<!cir.record<struct "A">>, !cir.record<struct "anon.2" {!cir.ptr<!cir.record<struct "B">>}>}>}>}>>}>
+// CHECK5: !cir.record<struct "C" {!cir.ptr<!cir.record<struct "A" {!rec_anon2E0, !cir.record<struct "B" {!cir.ptr<!cir.record<struct "B">>, !cir.record<struct "C">, !cir.record<union "anon.1" {!cir.ptr<!cir.record<struct "A">>, !cir.record<struct "anon.2" {!cir.ptr<!cir.record<struct "B">>}>}>}>}>>, !cir.ptr<!cir.record<struct "B" {!cir.ptr<!cir.record<struct "B">>, !cir.record<struct "C">, !cir.record<union "anon.1" {!cir.ptr<!cir.record<struct "A" {!rec_anon2E0, !cir.record<struct "B">}>>, !cir.record<struct "anon.2" {!cir.ptr<!cir.record<struct "B">>}>}>}>>, !cir.ptr<!cir.record<struct "C">>}>
+// CHECK5: !cir.record<struct "anon.2" {!cir.ptr<!cir.record<struct "B" {!cir.ptr<!cir.record<struct "B">>, !rec_C, !cir.record<union "anon.1" {!cir.ptr<!cir.record<struct "A" {!rec_anon2E0, !cir.record<struct "B">}>>, !cir.record<struct "anon.2">}>}>>}>
+// CHECK5: !cir.record<union "anon.1" {!cir.ptr<!cir.record<struct "A" {!rec_anon2E0, !cir.record<struct "B" {!cir.ptr<!cir.record<struct "B">>, !rec_C, !cir.record<union "anon.1">}>}>>, !rec_anon2E2}>
+// CHECK5: !cir.record<struct "B" {!cir.ptr<!cir.record<struct "B">>, !rec_C, !rec_anon2E1}>
+// CHECK5: !cir.record<struct "A" {!rec_anon2E0, !rec_B}>
+struct A {
+  struct {
+    struct A *a1;
+  };
+  struct B {
+    struct B *b1;
+    struct C {
+      struct A *a2;
+      struct B *b2;
+      struct C *c1;
+    } c;
+    union {
+      struct A *a2;
+      struct {
+        struct B *b3;
+      };
+    } u;
+  } b;
+};
+void test(struct A *a){};

clang/test/CIR/CodeGen/forward-enum.c

@@ -0,0 +1,16 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir -emit-cir %s -o %t.cir
+// RUN: FileCheck %s --input-file=%t.cir
+
+extern enum X x;
+void f(void) {
+  x;
+}
+
+enum X {
+  One,
+  Two
+};
+
+// CHECK: cir.global "private" external @x : !u32i
+// CHECK: cir.func{{.*}} @f
+// CHECK:   cir.get_global @x : !cir.ptr<!u32i>