[CIR] Add VTableAddrPointOp

This change adds the definition of VTableAddrPointOp and the related
AddressPointAttr to the CIR dialect, along with tests for the parsing
and verification of these elements.

Code to generate this operation will be added in a later change.

Author: andykaylor

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

@@ -516,4 +516,36 @@ def CIR_BitfieldInfoAttr : CIR_Attr<"BitfieldInfo", "bitfield_info"> {
   ];
 }
 
+//===----------------------------------------------------------------------===//
+// AddressPointAttr
+//===----------------------------------------------------------------------===//
+
+def CIR_AddressPointAttr : CIR_Attr<"AddressPoint", "address_point"> {
+  let summary = "Address point attribute";
+
+  let description = [{
+    Attribute specifying the address point within a C++ virtual table (vtable).
+
+    The `index` (vtable index) parameter identifies which vtable to use within a
+    vtable group, while the `offset` (address point index) specifies the offset
+    within that vtable where the address begins.
+
+    Example:
+    ```mlir
+    cir.global linkonce_odr @_ZTV1B = ...
+    ...
+    %3 = cir.vtable.address_point(@_ZTV1B,
+                                  address_point = <index = 0, offset = 2>)
+                                 : !cir.vptr
+    ```
+  }];
+
+  let parameters = (ins "int32_t":$index,
+                        "int32_t":$offset);
+
+  let assemblyFormat = [{
+    `<` struct($index, $offset) `>`
+  }];
+}
+
 #endif // CLANG_CIR_DIALECT_IR_CIRATTRS_TD

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

@@ -1691,6 +1691,49 @@ def CIR_GetGlobalOp : CIR_Op<"get_global", [
   }];
 }
 
+//===----------------------------------------------------------------------===//
+// VTableAddrPointOp
+//===----------------------------------------------------------------------===//
+
+def CIR_VTableAddrPointOp : CIR_Op<"vtable.address_point", [
+  Pure, DeclareOpInterfaceMethods<SymbolUserOpInterface>
+]> {
+  let summary = "Get the vtable (global variable) address point";
+  let description = [{
+    The `vtable.address_point` operation retrieves the "effective" address
+    (address point) of a C++ virtual table. An object internal `__vptr`
+    gets initializated on top of the value returned by this operation.
+
+    `address_point.index` (vtable index) provides the appropriate vtable within
+    the vtable group (as specified by Itanium ABI), and `address_point.offset`
+    (address point index) the actual address point within that vtable.
+
+    The return type is always `!cir.vptr`.
+
+    Example:
+    ```mlir
+    cir.global linkonce_odr @_ZTV1B = ...
+    ...
+    %3 = cir.vtable.address_point(@_ZTV1B,
+              address_point = <index = 0, offset = 2>) : !cir.vptr
+    ```
+  }];
+
+  let arguments = (ins
+    FlatSymbolRefAttr:$name,
+    CIR_AddressPointAttr:$address_point
+  );
+
+  let results = (outs Res<CIR_VPtrType, "", []>:$addr);
+
+  let assemblyFormat = [{
+    `(`
+      $name `,` `address_point` `=` $address_point
+    `)`
+    `:` qualified(type($addr)) attr-dict
+  }];
+}
+
 //===----------------------------------------------------------------------===//
 // SetBitfieldOp
 //===----------------------------------------------------------------------===//

clang/include/clang/CIR/MissingFeatures.h

@@ -253,6 +253,7 @@ struct MissingFeatures {
   static bool thunks() { return false; }
   static bool tryEmitAsConstant() { return false; }
   static bool typeChecks() { return false; }
+  static bool vtableInitializer() { return false; }
   static bool weakRefReference() { return false; }
   static bool writebacks() { return false; }
   static bool appleKext() { return false; }

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

@@ -1443,6 +1443,27 @@ cir::GetGlobalOp::verifySymbolUses(SymbolTableCollection &symbolTable) {
   return success();
 }
 
+//===----------------------------------------------------------------------===//
+// VTableAddrPointOp
+//===----------------------------------------------------------------------===//
+
+LogicalResult
+cir::VTableAddrPointOp::verifySymbolUses(SymbolTableCollection &symbolTable) {
+  StringRef name = getName();
+
+  // Verify that the result type underlying pointer type matches the type of
+  // the referenced cir.global or cir.func op.
+  auto op = symbolTable.lookupNearestSymbolFrom<GlobalOp>(*this, getNameAttr());
+  if (!op)
+    return emitOpError("'")
+           << name << "' does not reference a valid cir.global";
+  std::optional<mlir::Attribute> init = op.getInitialValue();
+  if (!init)
+    return success();
+  assert(!cir::MissingFeatures::vtableInitializer());
+  return success();
+}
+
 //===----------------------------------------------------------------------===//
 // FuncOp
 //===----------------------------------------------------------------------===//

clang/test/CIR/IR/invalid-vtable.cir

@@ -0,0 +1,9 @@
+// RUN: cir-opt %s -verify-diagnostics
+
+!s8i = !cir.int<s, 8>
+!u32i = !cir.int<u, 32>
+cir.func @reference_unknown_vtable() {
+  // expected-error @below {{'cir.vtable.address_point' op 'some_vtable' does not reference a valid cir.global}}
+  %0 = cir.vtable.address_point(@some_vtable, address_point = <index = 0, offset = 2>) : !cir.vptr
+  cir.return
+}

clang/test/CIR/IR/vtable-addrpt.cir

@@ -0,0 +1,23 @@
+// RUN: cir-opt %s | FileCheck %s
+
+// Test the parsing and printing of a constructor that uses a vtable addess_point op.
+
+!u32i = !cir.int<u, 32>
+!u8i = !cir.int<u, 8>
+!rec_anon_struct = !cir.record<struct  {!cir.array<!cir.ptr<!u8i> x 4>}>
+!rec_S = !cir.record<struct "S" {!cir.vptr}>
+
+module {
+  cir.global "private" external @_ZTV1S : !rec_anon_struct {alignment = 8 : i64}
+  cir.func @_ZN1SC2Ev(%arg0: !cir.ptr<!rec_S>) {
+    %0 = cir.alloca !cir.ptr<!rec_S>, !cir.ptr<!cir.ptr<!rec_S>>, ["this", init] {alignment = 8 : i64}
+    cir.store %arg0, %0 : !cir.ptr<!rec_S>, !cir.ptr<!cir.ptr<!rec_S>>
+    %1 = cir.load %0 : !cir.ptr<!cir.ptr<!rec_S>>, !cir.ptr<!rec_S>
+    %2 = cir.vtable.address_point(@_ZTV1S, address_point = <index = 0, offset = 2>) : !cir.vptr
+    %3 = cir.cast(bitcast, %1 : !cir.ptr<!rec_S>), !cir.ptr<!cir.vptr>
+    cir.store align(8) %2, %3 : !cir.vptr, !cir.ptr<!cir.vptr>
+    cir.return
+  }
+}
+
+// CHECK: cir.vtable.address_point(@_ZTV1S, address_point = <index = 0, offset = 2>) : !cir.vptr