From a9976d3b192690db20f59dc44099ac4ca939bdb7 Mon Sep 17 00:00:00 2001
From: John McCall <rjmccall@apple.com>
Date: Fri, 21 May 2010 01:18:57 +0000
Subject: [PATCH] When emitting an lvalue for an anonymous struct or union
 member during class initialization, drill down through an arbitrary number of
 anonymous records.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@104310 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/CGClass.cpp                       |  6 ++--
 lib/CodeGen/CGExpr.cpp                        | 29 +++++++++++++++++++
 lib/CodeGen/CodeGenFunction.h                 |  3 ++
 .../anonymous-union-member-initializer.cpp    | 26 +++++++++++++++++
 4 files changed, 62 insertions(+), 2 deletions(-)

diff --git a/lib/CodeGen/CGClass.cpp b/lib/CodeGen/CGClass.cpp
index 72d95b8556..82c72288d9 100644
--- a/lib/CodeGen/CGClass.cpp
+++ b/lib/CodeGen/CGClass.cpp
@@ -446,13 +446,15 @@ static void EmitMemberInitializer(CodeGenFunction &CGF,
   QualType FieldType = CGF.getContext().getCanonicalType(Field->getType());
 
   llvm::Value *ThisPtr = CGF.LoadCXXThis();
-  LValue LHS = CGF.EmitLValueForFieldInitialization(ThisPtr, Field, 0);
+  LValue LHS;
   
   // If we are initializing an anonymous union field, drill down to the field.
   if (MemberInit->getAnonUnionMember()) {
     Field = MemberInit->getAnonUnionMember();
-    LHS = CGF.EmitLValueForField(LHS.getAddress(), Field, 0);
+    LHS = CGF.EmitLValueForAnonRecordField(ThisPtr, Field, 0);
     FieldType = Field->getType();
+  } else {
+    LHS = CGF.EmitLValueForFieldInitialization(ThisPtr, Field, 0);
   }
 
   // FIXME: If there's no initializer and the CXXBaseOrMemberInitializer
diff --git a/lib/CodeGen/CGExpr.cpp b/lib/CodeGen/CGExpr.cpp
index 80d38f250d..74e64e59a5 100644
--- a/lib/CodeGen/CGExpr.cpp
+++ b/lib/CodeGen/CGExpr.cpp
@@ -1611,6 +1611,35 @@ LValue CodeGenFunction::EmitLValueForBitfield(llvm::Value* BaseValue,
                              Field->getType().getCVRQualifiers()|CVRQualifiers);
 }
 
+/// EmitLValueForAnonRecordField - Given that the field is a member of
+/// an anonymous struct or union buried inside a record, and given
+/// that the base value is a pointer to the enclosing record, derive
+/// an lvalue for the ultimate field.
+LValue CodeGenFunction::EmitLValueForAnonRecordField(llvm::Value *BaseValue,
+                                                     const FieldDecl *Field,
+                                                     unsigned CVRQualifiers) {
+  llvm::SmallVector<const FieldDecl *, 8> Path;
+  Path.push_back(Field);
+
+  while (Field->getParent()->isAnonymousStructOrUnion()) {
+    const ValueDecl *VD = Field->getParent()->getAnonymousStructOrUnionObject();
+    if (!isa<FieldDecl>(VD)) break;
+    Field = cast<FieldDecl>(VD);
+    Path.push_back(Field);
+  }
+
+  llvm::SmallVectorImpl<const FieldDecl*>::reverse_iterator
+    I = Path.rbegin(), E = Path.rend();
+  while (true) {
+    LValue LV = EmitLValueForField(BaseValue, *I, CVRQualifiers);
+    if (++I == E) return LV;
+
+    assert(LV.isSimple());
+    BaseValue = LV.getAddress();
+    CVRQualifiers |= LV.getVRQualifiers();
+  }
+}
+
 LValue CodeGenFunction::EmitLValueForField(llvm::Value* BaseValue,
                                            const FieldDecl* Field,
                                            unsigned CVRQualifiers) {
diff --git a/lib/CodeGen/CodeGenFunction.h b/lib/CodeGen/CodeGenFunction.h
index 077b8169f1..048bd0918a 100644
--- a/lib/CodeGen/CodeGenFunction.h
+++ b/lib/CodeGen/CodeGenFunction.h
@@ -1052,6 +1052,9 @@ public:
   
   llvm::Value *EmitIvarOffset(const ObjCInterfaceDecl *Interface,
                               const ObjCIvarDecl *Ivar);
+  LValue EmitLValueForAnonRecordField(llvm::Value* Base,
+                                      const FieldDecl* Field,
+                                      unsigned CVRQualifiers);
   LValue EmitLValueForField(llvm::Value* Base, const FieldDecl* Field,
                             unsigned CVRQualifiers);
   
diff --git a/test/CodeGenCXX/anonymous-union-member-initializer.cpp b/test/CodeGenCXX/anonymous-union-member-initializer.cpp
index bd816a4a44..a4da2c04fd 100644
--- a/test/CodeGenCXX/anonymous-union-member-initializer.cpp
+++ b/test/CodeGenCXX/anonymous-union-member-initializer.cpp
@@ -52,3 +52,29 @@ namespace test2 {
   // CHECK: store i32 10
   // CHECK: }
 }
+
+namespace test3 {
+  struct A {
+    union {
+      mutable char fibers[100];
+      struct {
+        void (*callback)(void*);
+        void *callback_value;
+      };
+    };
+
+    A();
+  };
+
+  A::A() : callback(0), callback_value(0) {}
+  // CHECK: define void @ZN5test31AC2Ev(
+  // CHECK: [[THIS:%.*]] = load
+  // CHECK-NEXT: [[UNION:%.*]] = getelementptr inbounds {{.*}} [[THIS]], i32 0, i32 0
+  // CHECK-NEXT: [[STRUCT:%.*]] = getelementptr inbounds {{.*}} [[UNION]], i32 0, i32 0
+  // CHECK-NEXT: [[CALLBACK:%.*]] = getelementptr inbounds {{.*}} [[STRUCT]], i32 0, i32 0
+  // CHECK-NEXT: store void (i8*)* null, void (i8*)** [[CALLBACK]]
+  // CHECK-NEXT: [[UNION:%.*]] = getelementptr inbounds {{.*}} [[THIS]], i32 0, i32 0
+  // CHECK-NEXT: [[STRUCT:%.*]] = getelementptr inbounds {{.*}} [[UNION]], i32 0, i32 0
+  // CHECK-NEXT: [[CVALUE:%.*]] = getelementptr inbounds {{.*}} [[STRUCT]], i32 0, i32 0
+  // CHECK-NEXT: store i8* null, void i8** [[CVALUE]]
+}
-- 
2.40.0