[Clang][CodeGen] Do not set inbounds in EmitMemberDataPointerAddress when the base pointer is null

Author: dtcxzyw

clang/lib/CodeGen/ItaniumCXXABI.cpp

@@ -872,9 +872,14 @@ llvm::Value *ItaniumCXXABI::EmitMemberDataPointerAddress(
 
   CGBuilderTy &Builder = CGF.Builder;
 
-  // Apply the offset, which we assume is non-null.
-  return Builder.CreateInBoundsGEP(CGF.Int8Ty, Base.emitRawPointer(CGF), MemPtr,
-                                   "memptr.offset");
+  // Apply the offset.
+  // Specially, we don't add inbounds flags if the base pointer is a constant
+  // null. This is a workaround for old-style container_of macros.
+  llvm::Value *BaseAddr = Base.emitRawPointer(CGF);
+  return Builder.CreateGEP(CGF.Int8Ty, BaseAddr, MemPtr, "memptr.offset",
+                           isa<llvm::ConstantPointerNull>(BaseAddr)
+                               ? llvm::GEPNoWrapFlags::none()
+                               : llvm::GEPNoWrapFlags::inBounds());
 }
 
 // See if it's possible to return a constant signed pointer.

clang/lib/CodeGen/MicrosoftCXXABI.cpp

@@ -3265,9 +3265,13 @@ llvm::Value *MicrosoftCXXABI::EmitMemberDataPointerAddress(
     Addr = Base.emitRawPointer(CGF);
   }
 
-  // Apply the offset, which we assume is non-null.
-  return Builder.CreateInBoundsGEP(CGF.Int8Ty, Addr, FieldOffset,
-                                   "memptr.offset");
+  // Apply the offset.
+  // Specially, we don't add inbounds flags if the base pointer is a constant
+  // null. This is a workaround for old-style container_of macros.
+  return Builder.CreateGEP(CGF.Int8Ty, Addr, FieldOffset, "memptr.offset",
+                           isa<llvm::ConstantPointerNull>(Addr)
+                               ? llvm::GEPNoWrapFlags::none()
+                               : llvm::GEPNoWrapFlags::inBounds());
 }
 
 llvm::Value *

clang/test/CodeGenCXX/microsoft-abi-member-pointers.cpp

@@ -964,3 +964,24 @@ static_assert(sizeof(b::d) == 16, "");
 static_assert(sizeof(void (a<int>::*)()) == 16, "");
 #endif
 }
+
+namespace ContainerOf {
+  using size_t = unsigned long long;
+
+  struct List {
+    int data;
+  };
+
+  struct Node {
+    int data;
+    struct List list1;
+    struct List list2;
+  };
+
+  // CHECK-LABEL: define{{.*}} ptr @"?getOwner@ContainerOf@@
+  // CHECK: %memptr.offset = getelementptr i8, ptr null, {{.*}}
+  Node* getOwner(List *list, List Node::*member) {
+    size_t offset = reinterpret_cast<size_t>(&((Node*)nullptr->*member));
+    return reinterpret_cast<Node*>(reinterpret_cast<char*>(list) - offset);
+  }
+}

clang/test/CodeGenCXX/pointers-to-data-members.cpp

@@ -265,3 +265,24 @@ namespace PR47864 {
   struct D : B { int m; };
   auto x = (int B::*)&D::m;
 }
+
+namespace ContainerOf {
+  using size_t = unsigned long long;
+
+  struct List {
+    int data;
+  };
+
+  struct Node {
+    int data;
+    struct List list1;
+    struct List list2;
+  };
+
+  // CHECK-LABEL: define{{.*}} ptr @_ZN11ContainerOf8getOwnerEPNS_4ListEMNS_4NodeES0_
+  // CHECK: %memptr.offset = getelementptr i8, ptr null, i64 {{.*}}
+  Node* getOwner(List *list, List Node::*member) {
+    size_t offset = reinterpret_cast<size_t>(&((Node*)nullptr->*member));
+    return reinterpret_cast<Node*>(reinterpret_cast<char*>(list) - offset);
+  }
+}