[MS-ABI]V-base dtor called more than needed when throw happens in v-b…

…ase ctor in window. Need add "complete object flag" check in eh cleanup code.

The problem only happen on window ( A MS-ABI issuer )

The nature of the problem is virtual base dtor called more than it is needed after exception throw in inheriting base class(with virtual bases) ctor.

The root problem is when throw happen, not all virtual base classes have been contructed, so not all virtual base dtors are need to call for ehcleanup.

clang has code to handle vbase initialization: basically add check for "complete object flag" before call to v-base ctor.
But that part is missing for cleanup code.

To fix this add similar code as v-base init to cleanup code, same algorithm.

1> Add new routine:
EmitDtorCompleteObjectHandler

With corresponding to EmitCtorCompleteObjectHandler

2> In the EmitDestructorCal
Call EmitDtorCompleteObjectHandler when generate ehcleanup inside ctor.

Just add check for "complete object flag" before call to v-base dtor.

Without my change:
ehcleanup: ; preds = %ctor.skip_vbases

%13 = cleanuppad within none [], !dbg !66
%14 = bitcast %struct.class_0* %this1 to i8*, !dbg !66
%15 = getelementptr inbounds i8, i8* %14, i64 8, !dbg !66
%16 = bitcast i8* %15 to %struct.class_2*, !dbg !66
call void @"\01??1class_2@@UEAA@XZ"(%struct.class_2* %16) #6 [ "funclet"(token

%13) ], !dbg !66

cleanupret from %13 unwind to caller, !dbg !66

with my change:
ehcleanup: ; preds = %ctor.skip_vbases

%13 = cleanuppad within none [], !dbg !66
%14 = bitcast %struct.class_0* %this1 to i8*, !dbg !66
%15 = getelementptr inbounds i8, i8* %14, i64 8, !dbg !66
%16 = bitcast i8* %15 to %struct.class_2*, !dbg !66
%is_complete_object4 = icmp ne i32 %is_most_derived2, 0, !dbg !66
br i1 %is_complete_object4, label %Dtor.dtor_vbase, label %Dtor.skip_vbase, !d

bg !66

Dtor.dtor_vbase: ; preds = %ehcleanup

call void @"\01??1class_2@@UEAA@XZ"(%struct.class_2* %16) #6 [ "funclet"(token

%13) ], !dbg !66

br label %Dtor.skip_vbase, !dbg !66

Dtor.skip_vbase: ; preds = %Dtor.dtor_vbase, %ehcleanup

cleanupret from %13 unwind to caller, !dbg !66

Please let me know you need more info.

Patch by Jennifer Yu.

Differential Revision: https://reviews.llvm.org/D27358



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@288869 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/MicrosoftCXXABI.cpp

@@ -165,6 +165,9 @@ class MicrosoftCXXABI : public CGCXXABI {
   llvm::BasicBlock *
   EmitCtorCompleteObjectHandler(CodeGenFunction &CGF,
                                 const CXXRecordDecl *RD) override;
+
+  llvm::BasicBlock *
+  EmitDtorCompleteObjectHandler(CodeGenFunction &CGF);
 
   void initializeHiddenVirtualInheritanceMembers(CodeGenFunction &CGF,
                                               const CXXRecordDecl *RD) override;
@@ -1135,6 +1138,25 @@ MicrosoftCXXABI::EmitCtorCompleteObjectHandler(CodeGenFunction &CGF,
   return SkipVbaseCtorsBB;
 }
 
+llvm::BasicBlock *
+MicrosoftCXXABI::EmitDtorCompleteObjectHandler(CodeGenFunction &CGF) {
+  llvm::Value *IsMostDerivedClass = getStructorImplicitParamValue(CGF);
+  assert(IsMostDerivedClass &&
+         "ctor for a class with virtual bases must have an implicit parameter");
+  llvm::Value *IsCompleteObject =
+      CGF.Builder.CreateIsNotNull(IsMostDerivedClass, "is_complete_object");
+
+  llvm::BasicBlock *CallVbaseDtorsBB = CGF.createBasicBlock("Dtor.dtor_vbases");
+  llvm::BasicBlock *SkipVbaseDtorsBB = CGF.createBasicBlock("Dtor.skip_vbases");
+  CGF.Builder.CreateCondBr(IsCompleteObject,
+                           CallVbaseDtorsBB, SkipVbaseDtorsBB);
+
+  CGF.EmitBlock(CallVbaseDtorsBB);
+  // CGF will put the base dtor calls in this basic block for us later.
+
+  return SkipVbaseDtorsBB;
+}
+
 void MicrosoftCXXABI::initializeHiddenVirtualInheritanceMembers(
     CodeGenFunction &CGF, const CXXRecordDecl *RD) {
   // In most cases, an override for a vbase virtual method can adjust
@@ -1512,11 +1534,21 @@ void MicrosoftCXXABI::EmitDestructorCall(CodeGenFunction &CGF,
     This = adjustThisArgumentForVirtualFunctionCall(CGF, GlobalDecl(DD, Type),
                                                     This, false);
   }
+
+  llvm::BasicBlock *BaseDtorEndBB = nullptr;
+  if (ForVirtualBase && isa<CXXConstructorDecl>(CGF.CurCodeDecl)) {
+    BaseDtorEndBB = EmitDtorCompleteObjectHandler(CGF);
+  }  
 
   CGF.EmitCXXDestructorCall(DD, Callee, This.getPointer(),
                             /*ImplicitParam=*/nullptr,
                             /*ImplicitParamTy=*/QualType(), nullptr,
                             getFromDtorType(Type));
+  if (BaseDtorEndBB) {
+    // Complete object handler should continue to be the remaining 
+    CGF.Builder.CreateBr(BaseDtorEndBB);
+    CGF.EmitBlock(BaseDtorEndBB);
+  } 
 }
 
 void MicrosoftCXXABI::emitVTableTypeMetadata(const VPtrInfo &Info,

test/CodeGenCXX/microsoft-abi-eh-cleanups.cpp

@@ -278,3 +278,38 @@ void f() {
 // WIN32-LIFETIME: %[[bc2:.*]] = bitcast %"struct.lifetime_marker::C"* %[[c]] to i8*
 // WIN32-LIFETIME: call void @llvm.lifetime.end(i64 1, i8* %[[bc2]])
 }
+
+struct class_2 {
+  class_2();
+  virtual ~class_2();
+};
+struct class_1 : virtual class_2 {
+  class_1(){throw "Unhandled exception";}
+  virtual ~class_1() {}
+};
+struct class_0 : class_1 {
+  class_0() ;
+  virtual ~class_0() {}
+};
+
+class_0::class_0() {
+  // WIN32: define x86_thiscallcc %struct.class_0* @"\01??0class_0@@QAE@XZ"(%struct.class_0* returned %this, i32 %is_most_derived) 
+  // WIN32: store i32 %is_most_derived, i32* %[[IS_MOST_DERIVED_VAR:.*]], align 4
+  // WIN32: %[[IS_MOST_DERIVED_VAL:.*]] = load i32, i32* %[[IS_MOST_DERIVED_VAR]]
+  // WIN32: %[[SHOULD_CALL_VBASE_CTORS:.*]] = icmp ne i32 %[[IS_MOST_DERIVED_VAL]], 0
+  // WIN32: br i1 %[[SHOULD_CALL_VBASE_CTORS]], label %[[INIT_VBASES:.*]], label %[[SKIP_VBASES:.*]]
+  // WIN32: [[INIT_VBASES]]
+  // WIN32: br label %[[SKIP_VBASES]]
+  // WIN32: [[SKIP_VBASES]]
+// ehcleanup:
+  // WIN32: %[[CLEANUPPAD:.*]] = cleanuppad within none []
+  // WIN32-NEXT: bitcast %{{.*}}* %{{.*}} to i8*
+  // WIN32-NEXT: getelementptr inbounds i8, i8* %{{.*}}, i{{.*}} {{.}} 
+  // WIN32-NEXT: bitcast i8* %{{.*}} to %{{.*}}*
+  // WIN32-NEXT: %[[SHOULD_CALL_VBASE_DTOR:.*]] = icmp ne i32 %[[IS_MOST_DERIVED_VAL]], 0
+  // WIN32-NEXT: br i1 %[[SHOULD_CALL_VBASE_DTOR]], label %[[DTOR_VBASE:.*]], label %[[SKIP_VBASE:.*]]
+  // WIN32: [[DTOR_VBASE]]
+  // WIN32-NEXT: call x86_thiscallcc void @"\01??1class_2@@UAE@XZ"
+  // WIN32: br label %[[SKIP_VBASE]]
+  // WIN32: [[SKIP_VBASE]]
+}