[CIR][CIRGen][TBAA] Add support for vtable pointer (#1463)

Author: PikachuHyA

clang/include/clang/CIR/Dialect/IR/CIRTBAAAttrs.td

@@ -15,6 +15,17 @@ def CIR_TBAAOmnipotentChar
   let summary = "Describes a special scalar type, the omnipotent char type.";
 }
 
+//===----------------------------------------------------------------------===//
+// TBAAVTablePointerAttr
+//===----------------------------------------------------------------------===//
+
+def CIR_TBAAVTablePointerAttr
+    : CIR_Attr<"TBAAVTablePointer", "tbaa_vptr", [], "TBAAAttr"> {
+  let summary = "Describes a special scalar type, the vtable pointer type.";
+  let parameters = (ins CIR_AnyType:$type);
+  let assemblyFormat = "`<` struct(params) `>`";
+}
+
 //===----------------------------------------------------------------------===//
 // TBAAScalarAttr
 //===----------------------------------------------------------------------===//
@@ -140,7 +151,8 @@ def CIR_TBAAStructAttr : CIR_Attr<"TBAAStruct",
 
 def CIR_AnyTBAAAttr : AnyAttrOf<[
   CIR_TBAAAttr, 
-  CIR_TBAAOmnipotentChar, 
+  CIR_TBAAOmnipotentChar,
+  CIR_TBAAVTablePointerAttr,
   CIR_TBAAScalarAttr,
   CIR_TBAAStructAttr,
   CIR_TBAATagAttr

clang/include/clang/CIR/MissingFeatures.h

@@ -60,7 +60,6 @@ struct MissingFeatures {
   static bool tbaa() { return false; }
   static bool tbaaStruct() { return false; }
   static bool tbaaTagForStruct() { return false; }
-  static bool tbaaVTablePtr() { return false; }
   static bool tbaaIncompleteType() { return false; }
   static bool tbaaMergeTBAAInfo() { return false; }
   static bool tbaaMayAlias() { return false; }

clang/lib/CIR/CodeGen/CIRGenTBAA.cpp

@@ -324,8 +324,10 @@ TBAAAccessInfo CIRGenTBAA::getAccessInfo(clang::QualType accessType) {
 }
 
 TBAAAccessInfo CIRGenTBAA::getVTablePtrAccessInfo(mlir::Type vtablePtrType) {
-  assert(!cir::MissingFeatures::tbaaVTablePtr());
-  return TBAAAccessInfo();
+  const mlir::DataLayout dataLayout(moduleOp);
+  auto size = dataLayout.getTypeSize(vtablePtrType);
+  return TBAAAccessInfo(
+      cir::TBAAVTablePointerAttr::get(mlirContext, vtablePtrType), size);
 }
 
 mlir::ArrayAttr CIRGenTBAA::getTBAAStructInfo(clang::QualType qty) {

clang/lib/CIR/Dialect/IR/CIRDialect.cpp

@@ -108,7 +108,8 @@ struct CIROpAsmDialectInterface : public OpAsmDialectInterface {
       return AliasResult::FinalAlias;
     }
     return TypeSwitch<Attribute, AliasResult>(attr)
-        .Case<cir::TBAAAttr, cir::TBAAOmnipotentCharAttr, cir::TBAAScalarAttr,
+        .Case<cir::TBAAAttr, cir::TBAAOmnipotentCharAttr,
+              cir::TBAAVTablePointerAttr, cir::TBAAScalarAttr,
               cir::TBAAStructAttr, cir::TBAATagAttr>([&](auto attr) {
           os << decltype(attr)::getMnemonic();
           return AliasResult::OverridableAlias;

clang/lib/CIR/Lowering/DirectToLLVM/LowerTBAAToLLVM.cpp

@@ -4,6 +4,7 @@
 #include "mlir/IR/BuiltinAttributes.h"
 #include "mlir/IR/MLIRContext.h"
 #include "mlir/Interfaces/DataLayoutInterfaces.h"
+#include "mlir/Support/LLVM.h"
 #include "clang/CIR/Dialect/IR/CIRAttrs.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/Support/ErrorHandling.h"
@@ -22,6 +23,11 @@ class CIRToLLVMTBAAAttrLowering {
     if (auto charAttr = mlir::dyn_cast<cir::TBAAOmnipotentCharAttr>(tbaa)) {
       return getChar();
     }
+    if (auto vptrAttr = mlir::dyn_cast<cir::TBAAVTablePointerAttr>(tbaa)) {
+      mlir::DataLayout layout;
+      return createScalarTypeNode("vtable pointer", getRoot(),
+                                  layout.getTypeSize(vptrAttr.getType()));
+    }
     if (auto scalarAttr = mlir::dyn_cast<cir::TBAAScalarAttr>(tbaa)) {
       mlir::DataLayout layout;
       auto size = layout.getTypeSize(scalarAttr.getType());

clang/test/CIR/CodeGen/tbaa-vptr.cpp

@@ -1,7 +1,15 @@
 // RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir -emit-cir %s -o %t.cir -O1
 // RUN: FileCheck --check-prefix=CIR --input-file=%t.cir %s
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir -emit-llvm %s -o %t.ll -O1
+// RUN: FileCheck --check-prefix=LLVM --input-file=%t.ll %s
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir -emit-llvm %s -o %t.ll -O1 -relaxed-aliasing
+// RUN: FileCheck --check-prefix=NO-TBAA --input-file=%t.ll %s
+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fclangir -emit-llvm %s -o %t.ll -O0
+// RUN: FileCheck --check-prefix=NO-TBAA --input-file=%t.ll %s
 
-// CIR-NOT: #tbaa
+// NO-TBAA-NOT: !tbaa
+
+// CIR: #tbaa[[VPTR:.*]] = #cir.tbaa_vptr<type = !cir.ptr<!cir.ptr<!cir.func<() -> !u32i>>>>
 
 struct Member {
   ~Member();
@@ -16,3 +24,11 @@ struct B : A {
   virtual ~B();
 };
 B::~B() { }
+
+// CIR-LABEL: _ZN1BD2Ev
+// CIR: cir.store %{{.*}}, %{{.*}} : !cir.ptr<!cir.ptr<!cir.func<() -> !u32i>>>, !cir.ptr<!cir.ptr<!cir.ptr<!cir.func<() -> !u32i>>>> tbaa(#tbaa[[VPTR]])
+
+// LLVM-LABEL: _ZN1BD2Ev
+// LLVM: store ptr getelementptr inbounds nuw (i8, ptr @_ZTV1B, i64 16), ptr %{{.*}}, align 8, !tbaa ![[TBAA_VPTR:.*]]
+// LLVM: ![[TBAA_VPTR]] = !{![[TBAA_VPTR_PARENT:.*]], ![[TBAA_VPTR_PARENT]], i64 0}
+// LLVM: ![[TBAA_VPTR_PARENT]] = !{!"vtable pointer", !