[CIR] Add CIR vtable attribute #154415

andykaylor · 2025-08-19T19:39:06Z

This adds the #cir.vtable attribute definition and verification. Generation of the vtable will be implemented in a later change.

llvmbot · 2025-08-19T19:39:37Z

@llvm/pr-subscribers-clang

Author: Andy Kaylor (andykaylor)

Changes

This adds the #cir.vtable attribute definition and verification. Generation of the vtable will be implemented in a later change.

Full diff: https://github.com/llvm/llvm-project/pull/154415.diff

5 Files Affected:

(modified) clang/include/clang/CIR/Dialect/IR/CIRAttrs.td (+40)
(modified) clang/lib/CIR/Dialect/IR/CIRAttrs.cpp (+38)
(modified) clang/lib/CIR/Dialect/IR/CIRDialect.cpp (+2-1)
(modified) clang/test/CIR/IR/invalid-vtable.cir (+49-1)
(added) clang/test/CIR/IR/vtable-attr.cir (+12)

diff --git a/clang/include/clang/CIR/Dialect/IR/CIRAttrs.td b/clang/include/clang/CIR/Dialect/IR/CIRAttrs.td
index 89b4d25b37ba6..c57fabeccc296 100644
--- a/clang/include/clang/CIR/Dialect/IR/CIRAttrs.td
+++ b/clang/include/clang/CIR/Dialect/IR/CIRAttrs.td
@@ -496,6 +496,46 @@ def CIR_GlobalViewAttr : CIR_Attr<"GlobalView", "global_view", [
   }];
 }
 
+//===----------------------------------------------------------------------===//
+// VTableAttr
+//===----------------------------------------------------------------------===//
+
+def VTableAttr : CIR_Attr<"VTable", "vtable", [TypedAttrInterface]> {
+  let summary = "Represents a C++ vtable";
+  let description = [{
+    Wraps a #cir.const_record containing vtable data.
+
+    Example:
+    ```
+    cir.global linkonce_odr @_ZTV1B = #cir.vtable<<
+        {#cir.const_array<[#cir.null : !cir.ptr<i8>,
+         #cir.global_view<@_ZTI1B> : !cir.ptr<i8>,
+         #cir.global_view<@_ZN1BD1Ev> : !cir.ptr<i8>,
+         #cir.global_view<@_ZN1BD0Ev> : !cir.ptr<i8>,
+         #cir.global_view<@_ZNK1A5quackEv> : !cir.ptr<i8>]>
+         : !cir.array<!cir.ptr<i8> x 5>}>>
+      : !cir.record<"", !cir.array<!cir.ptr<i8> x 5>>
+    ```
+  }];
+
+  // `vtable_data` is a const record with one element, containing an array of
+  // vtable information.
+  let parameters = (ins AttributeSelfTypeParameter<"">:$type,
+                        "mlir::ArrayAttr":$vtable_data);
+
+  let builders = [
+    AttrBuilderWithInferredContext<(ins "mlir::Type":$type,
+                                        "mlir::ArrayAttr":$vtable_data), [{
+      return $_get(type.getContext(), type, vtable_data);
+    }]>
+  ];
+
+  let genVerifyDecl = 1;
+  let assemblyFormat = [{
+    `<` custom<RecordMembers>($vtable_data) `>`
+  }];
+}
+
 //===----------------------------------------------------------------------===//
 // ConstComplexAttr
 //===----------------------------------------------------------------------===//
diff --git a/clang/lib/CIR/Dialect/IR/CIRAttrs.cpp b/clang/lib/CIR/Dialect/IR/CIRAttrs.cpp
index 5f53a6335f37d..9050db5efc977 100644
--- a/clang/lib/CIR/Dialect/IR/CIRAttrs.cpp
+++ b/clang/lib/CIR/Dialect/IR/CIRAttrs.cpp
@@ -424,6 +424,44 @@ cir::ConstVectorAttr::verify(function_ref<InFlightDiagnostic()> emitError,
   return elementTypeCheck;
 }
 
+//===----------------------------------------------------------------------===//
+// CIR VTableAttr
+//===----------------------------------------------------------------------===//
+
+LogicalResult cir::VTableAttr::verify(
+    llvm::function_ref<mlir::InFlightDiagnostic()> emitError, mlir::Type type,
+    mlir::ArrayAttr vtableData) {
+  auto sTy = mlir::dyn_cast_if_present<cir::RecordType>(type);
+  if (!sTy)
+    return emitError() << "expected !cir.record type result";
+  if (sTy.getMembers().empty() || vtableData.empty())
+    return emitError() << "expected record type with one or more subtype";
+
+  for (size_t i = 0; i < sTy.getMembers().size(); ++i) {
+    auto constArrayAttr = mlir::dyn_cast<cir::ConstArrayAttr>(vtableData[i]);
+    if (!constArrayAttr)
+      return emitError() << "expected constant array subtype";
+
+    if (cir::ConstRecordAttr::verify(emitError, type, vtableData).failed())
+      return failure();
+
+    LogicalResult eltTypeCheck = success();
+    auto arrayElts = mlir::cast<ArrayAttr>(constArrayAttr.getElts());
+    arrayElts.walkImmediateSubElements(
+        [&](Attribute attr) {
+          if (mlir::isa<ConstPtrAttr, GlobalViewAttr>(attr))
+            return;
+
+          eltTypeCheck = emitError()
+                         << "expected GlobalViewAttr or ConstPtrAttr";
+        },
+        [&](Type type) {});
+    if (eltTypeCheck.failed())
+      return eltTypeCheck;
+  }
+  return success();
+}
+
 //===----------------------------------------------------------------------===//
 // CIR Dialect
 //===----------------------------------------------------------------------===//
diff --git a/clang/lib/CIR/Dialect/IR/CIRDialect.cpp b/clang/lib/CIR/Dialect/IR/CIRDialect.cpp
index 72feee8709dc4..0a7a8793943aa 100644
--- a/clang/lib/CIR/Dialect/IR/CIRDialect.cpp
+++ b/clang/lib/CIR/Dialect/IR/CIRDialect.cpp
@@ -342,7 +342,8 @@ static LogicalResult checkConstantTypes(mlir::Operation *op, mlir::Type opType,
 
   if (mlir::isa<cir::ConstArrayAttr, cir::ConstVectorAttr,
                 cir::ConstComplexAttr, cir::ConstRecordAttr,
-                cir::GlobalViewAttr, cir::PoisonAttr>(attrType))
+                cir::GlobalViewAttr, cir::PoisonAttr, cir::VTableAttr>(
+          attrType))
     return success();
 
   assert(isa<TypedAttr>(attrType) && "What else could we be looking at here?");
diff --git a/clang/test/CIR/IR/invalid-vtable.cir b/clang/test/CIR/IR/invalid-vtable.cir
index b3afb581b2048..0c8a36d26a0a1 100644
--- a/clang/test/CIR/IR/invalid-vtable.cir
+++ b/clang/test/CIR/IR/invalid-vtable.cir
@@ -1,4 +1,4 @@
-// RUN: cir-opt %s -verify-diagnostics
+// RUN: cir-opt %s -verify-diagnostics -split-input-file
 
 !s8i = !cir.int<s, 8>
 !u32i = !cir.int<u, 32>
@@ -7,3 +7,51 @@ cir.func @reference_unknown_vtable() {
   %0 = cir.vtable.address_point(@some_vtable, address_point = <index = 0, offset = 2>) : !cir.vptr
   cir.return
 }
+
+// -----
+
+!rec_S = !cir.record<struct "S" {!cir.vptr}>
+!u8i = !cir.int<u, 8>
+!rec_anon_struct = !cir.record<struct {!cir.array<!cir.ptr<!u8i> x 4>}>
+module {
+  // expected-error @below {{expected !cir.record type result}}
+  cir.global external @_ZTV1S = #cir.vtable<{#cir.const_array<[#cir.ptr<null> : !cir.ptr<!u8i>, #cir.ptr<null> : !cir.ptr<!u8i>, #cir.global_view<@_ZN1S3keyEv> : !cir.ptr<!u8i>, #cir.global_view<@_ZN1S6nonKeyEv> : !cir.ptr<!u8i>]> : !cir.array<!cir.ptr<!u8i> x 4>}> : !cir.ptr<!rec_anon_struct>
+  cir.func private dso_local @_ZN1S3keyEv(%arg0: !cir.ptr<!rec_S>)
+  cir.func private dso_local @_ZN1S6nonKeyEv(%arg0: !cir.ptr<!rec_S>)
+}
+
+// -----
+
+!rec_S = !cir.record<struct "S" {!cir.vptr}>
+!u8i = !cir.int<u, 8>
+!rec_anon_struct = !cir.record<struct  {}>
+module {
+  // expected-error @below {{expected record type with one or more subtype}}
+  cir.global external @_ZTV1S = #cir.vtable<{}> : !rec_anon_struct {alignment = 8 : i64}
+  cir.func private dso_local @_ZN1S3keyEv(%arg0: !cir.ptr<!rec_S>)
+  cir.func private dso_local @_ZN1S6nonKeyEv(%arg0: !cir.ptr<!rec_S>)
+}
+
+// -----
+
+!rec_S = !cir.record<struct "S" {!cir.vptr}>
+!u8i = !cir.int<u, 8>
+!rec_anon_struct = !cir.record<struct  {!cir.ptr<!u8i>}>
+module {
+  // expected-error @below {{expected constant array subtype}}
+  cir.global external @_ZTV1S = #cir.vtable<{#cir.ptr<null> : !cir.ptr<!u8i>}> : !rec_anon_struct {alignment = 8 : i64}
+  cir.func private dso_local @_ZN1S3keyEv(%arg0: !cir.ptr<!rec_S>)
+  cir.func private dso_local @_ZN1S6nonKeyEv(%arg0: !cir.ptr<!rec_S>)
+}
+
+// -----
+
+!rec_S = !cir.record<struct "S" {!cir.vptr}>
+!u64i = !cir.int<u, 64>
+!rec_anon_struct = !cir.record<struct  {!cir.array<!u64i x 4>}>
+module {
+  // expected-error @below {{expected GlobalViewAttr or ConstPtrAttr}}
+  cir.global external @_ZTV1S = #cir.vtable<{#cir.const_array<[#cir.int<1> : !u64i, #cir.int<1> : !u64i, #cir.int<3> : !u64i, #cir.int<4> : !u64i]> : !cir.array<!u64i x 4>}> : !rec_anon_struct {alignment = 8 : i64}
+  cir.func private dso_local @_ZN1S3keyEv(%arg0: !cir.ptr<!rec_S>)
+  cir.func private dso_local @_ZN1S6nonKeyEv(%arg0: !cir.ptr<!rec_S>)
+}
diff --git a/clang/test/CIR/IR/vtable-attr.cir b/clang/test/CIR/IR/vtable-attr.cir
new file mode 100644
index 0000000000000..4826bdcc90953
--- /dev/null
+++ b/clang/test/CIR/IR/vtable-attr.cir
@@ -0,0 +1,12 @@
+// RUN: cir-opt %s | FileCheck %s
+
+!rec_S = !cir.record<struct "S" {!cir.vptr}>
+!u8i = !cir.int<u, 8>
+!rec_anon_struct = !cir.record<struct  {!cir.array<!cir.ptr<!u8i> x 4>}>
+module {
+  cir.global external @_ZTV1S = #cir.vtable<{#cir.const_array<[#cir.ptr<null> : !cir.ptr<!u8i>, #cir.ptr<null> : !cir.ptr<!u8i>, #cir.global_view<@_ZN1S3keyEv> : !cir.ptr<!u8i>, #cir.global_view<@_ZN1S6nonKeyEv> : !cir.ptr<!u8i>]> : !cir.array<!cir.ptr<!u8i> x 4>}> : !rec_anon_struct {alignment = 8 : i64}
+  // CHECK: cir.global external @_ZTV1S = #cir.vtable<{#cir.const_array<[#cir.ptr<null> : !cir.ptr<!u8i>, #cir.ptr<null> : !cir.ptr<!u8i>, #cir.global_view<@_ZN1S3keyEv> : !cir.ptr<!u8i>, #cir.global_view<@_ZN1S6nonKeyEv> : !cir.ptr<!u8i>]> : !cir.array<!cir.ptr<!u8i> x 4>}> : !rec_anon_struct {alignment = 8 : i64}
+
+  cir.func private dso_local @_ZN1S3keyEv(%arg0: !cir.ptr<!rec_S>)
+  cir.func private dso_local @_ZN1S6nonKeyEv(%arg0: !cir.ptr<!rec_S>)
+}

llvmbot · 2025-08-19T19:39:38Z

@llvm/pr-subscribers-clangir

Author: Andy Kaylor (andykaylor)

Changes

This adds the #cir.vtable attribute definition and verification. Generation of the vtable will be implemented in a later change.

Full diff: https://github.com/llvm/llvm-project/pull/154415.diff

5 Files Affected:

(modified) clang/include/clang/CIR/Dialect/IR/CIRAttrs.td (+40)
(modified) clang/lib/CIR/Dialect/IR/CIRAttrs.cpp (+38)
(modified) clang/lib/CIR/Dialect/IR/CIRDialect.cpp (+2-1)
(modified) clang/test/CIR/IR/invalid-vtable.cir (+49-1)
(added) clang/test/CIR/IR/vtable-attr.cir (+12)

diff --git a/clang/include/clang/CIR/Dialect/IR/CIRAttrs.td b/clang/include/clang/CIR/Dialect/IR/CIRAttrs.td
index 89b4d25b37ba6..c57fabeccc296 100644
--- a/clang/include/clang/CIR/Dialect/IR/CIRAttrs.td
+++ b/clang/include/clang/CIR/Dialect/IR/CIRAttrs.td
@@ -496,6 +496,46 @@ def CIR_GlobalViewAttr : CIR_Attr<"GlobalView", "global_view", [
   }];
 }
 
+//===----------------------------------------------------------------------===//
+// VTableAttr
+//===----------------------------------------------------------------------===//
+
+def VTableAttr : CIR_Attr<"VTable", "vtable", [TypedAttrInterface]> {
+  let summary = "Represents a C++ vtable";
+  let description = [{
+    Wraps a #cir.const_record containing vtable data.
+
+    Example:
+    ```
+    cir.global linkonce_odr @_ZTV1B = #cir.vtable<<
+        {#cir.const_array<[#cir.null : !cir.ptr<i8>,
+         #cir.global_view<@_ZTI1B> : !cir.ptr<i8>,
+         #cir.global_view<@_ZN1BD1Ev> : !cir.ptr<i8>,
+         #cir.global_view<@_ZN1BD0Ev> : !cir.ptr<i8>,
+         #cir.global_view<@_ZNK1A5quackEv> : !cir.ptr<i8>]>
+         : !cir.array<!cir.ptr<i8> x 5>}>>
+      : !cir.record<"", !cir.array<!cir.ptr<i8> x 5>>
+    ```
+  }];
+
+  // `vtable_data` is a const record with one element, containing an array of
+  // vtable information.
+  let parameters = (ins AttributeSelfTypeParameter<"">:$type,
+                        "mlir::ArrayAttr":$vtable_data);
+
+  let builders = [
+    AttrBuilderWithInferredContext<(ins "mlir::Type":$type,
+                                        "mlir::ArrayAttr":$vtable_data), [{
+      return $_get(type.getContext(), type, vtable_data);
+    }]>
+  ];
+
+  let genVerifyDecl = 1;
+  let assemblyFormat = [{
+    `<` custom<RecordMembers>($vtable_data) `>`
+  }];
+}
+
 //===----------------------------------------------------------------------===//
 // ConstComplexAttr
 //===----------------------------------------------------------------------===//
diff --git a/clang/lib/CIR/Dialect/IR/CIRAttrs.cpp b/clang/lib/CIR/Dialect/IR/CIRAttrs.cpp
index 5f53a6335f37d..9050db5efc977 100644
--- a/clang/lib/CIR/Dialect/IR/CIRAttrs.cpp
+++ b/clang/lib/CIR/Dialect/IR/CIRAttrs.cpp
@@ -424,6 +424,44 @@ cir::ConstVectorAttr::verify(function_ref<InFlightDiagnostic()> emitError,
   return elementTypeCheck;
 }
 
+//===----------------------------------------------------------------------===//
+// CIR VTableAttr
+//===----------------------------------------------------------------------===//
+
+LogicalResult cir::VTableAttr::verify(
+    llvm::function_ref<mlir::InFlightDiagnostic()> emitError, mlir::Type type,
+    mlir::ArrayAttr vtableData) {
+  auto sTy = mlir::dyn_cast_if_present<cir::RecordType>(type);
+  if (!sTy)
+    return emitError() << "expected !cir.record type result";
+  if (sTy.getMembers().empty() || vtableData.empty())
+    return emitError() << "expected record type with one or more subtype";
+
+  for (size_t i = 0; i < sTy.getMembers().size(); ++i) {
+    auto constArrayAttr = mlir::dyn_cast<cir::ConstArrayAttr>(vtableData[i]);
+    if (!constArrayAttr)
+      return emitError() << "expected constant array subtype";
+
+    if (cir::ConstRecordAttr::verify(emitError, type, vtableData).failed())
+      return failure();
+
+    LogicalResult eltTypeCheck = success();
+    auto arrayElts = mlir::cast<ArrayAttr>(constArrayAttr.getElts());
+    arrayElts.walkImmediateSubElements(
+        [&](Attribute attr) {
+          if (mlir::isa<ConstPtrAttr, GlobalViewAttr>(attr))
+            return;
+
+          eltTypeCheck = emitError()
+                         << "expected GlobalViewAttr or ConstPtrAttr";
+        },
+        [&](Type type) {});
+    if (eltTypeCheck.failed())
+      return eltTypeCheck;
+  }
+  return success();
+}
+
 //===----------------------------------------------------------------------===//
 // CIR Dialect
 //===----------------------------------------------------------------------===//
diff --git a/clang/lib/CIR/Dialect/IR/CIRDialect.cpp b/clang/lib/CIR/Dialect/IR/CIRDialect.cpp
index 72feee8709dc4..0a7a8793943aa 100644
--- a/clang/lib/CIR/Dialect/IR/CIRDialect.cpp
+++ b/clang/lib/CIR/Dialect/IR/CIRDialect.cpp
@@ -342,7 +342,8 @@ static LogicalResult checkConstantTypes(mlir::Operation *op, mlir::Type opType,
 
   if (mlir::isa<cir::ConstArrayAttr, cir::ConstVectorAttr,
                 cir::ConstComplexAttr, cir::ConstRecordAttr,
-                cir::GlobalViewAttr, cir::PoisonAttr>(attrType))
+                cir::GlobalViewAttr, cir::PoisonAttr, cir::VTableAttr>(
+          attrType))
     return success();
 
   assert(isa<TypedAttr>(attrType) && "What else could we be looking at here?");
diff --git a/clang/test/CIR/IR/invalid-vtable.cir b/clang/test/CIR/IR/invalid-vtable.cir
index b3afb581b2048..0c8a36d26a0a1 100644
--- a/clang/test/CIR/IR/invalid-vtable.cir
+++ b/clang/test/CIR/IR/invalid-vtable.cir
@@ -1,4 +1,4 @@
-// RUN: cir-opt %s -verify-diagnostics
+// RUN: cir-opt %s -verify-diagnostics -split-input-file
 
 !s8i = !cir.int<s, 8>
 !u32i = !cir.int<u, 32>
@@ -7,3 +7,51 @@ cir.func @reference_unknown_vtable() {
   %0 = cir.vtable.address_point(@some_vtable, address_point = <index = 0, offset = 2>) : !cir.vptr
   cir.return
 }
+
+// -----
+
+!rec_S = !cir.record<struct "S" {!cir.vptr}>
+!u8i = !cir.int<u, 8>
+!rec_anon_struct = !cir.record<struct {!cir.array<!cir.ptr<!u8i> x 4>}>
+module {
+  // expected-error @below {{expected !cir.record type result}}
+  cir.global external @_ZTV1S = #cir.vtable<{#cir.const_array<[#cir.ptr<null> : !cir.ptr<!u8i>, #cir.ptr<null> : !cir.ptr<!u8i>, #cir.global_view<@_ZN1S3keyEv> : !cir.ptr<!u8i>, #cir.global_view<@_ZN1S6nonKeyEv> : !cir.ptr<!u8i>]> : !cir.array<!cir.ptr<!u8i> x 4>}> : !cir.ptr<!rec_anon_struct>
+  cir.func private dso_local @_ZN1S3keyEv(%arg0: !cir.ptr<!rec_S>)
+  cir.func private dso_local @_ZN1S6nonKeyEv(%arg0: !cir.ptr<!rec_S>)
+}
+
+// -----
+
+!rec_S = !cir.record<struct "S" {!cir.vptr}>
+!u8i = !cir.int<u, 8>
+!rec_anon_struct = !cir.record<struct  {}>
+module {
+  // expected-error @below {{expected record type with one or more subtype}}
+  cir.global external @_ZTV1S = #cir.vtable<{}> : !rec_anon_struct {alignment = 8 : i64}
+  cir.func private dso_local @_ZN1S3keyEv(%arg0: !cir.ptr<!rec_S>)
+  cir.func private dso_local @_ZN1S6nonKeyEv(%arg0: !cir.ptr<!rec_S>)
+}
+
+// -----
+
+!rec_S = !cir.record<struct "S" {!cir.vptr}>
+!u8i = !cir.int<u, 8>
+!rec_anon_struct = !cir.record<struct  {!cir.ptr<!u8i>}>
+module {
+  // expected-error @below {{expected constant array subtype}}
+  cir.global external @_ZTV1S = #cir.vtable<{#cir.ptr<null> : !cir.ptr<!u8i>}> : !rec_anon_struct {alignment = 8 : i64}
+  cir.func private dso_local @_ZN1S3keyEv(%arg0: !cir.ptr<!rec_S>)
+  cir.func private dso_local @_ZN1S6nonKeyEv(%arg0: !cir.ptr<!rec_S>)
+}
+
+// -----
+
+!rec_S = !cir.record<struct "S" {!cir.vptr}>
+!u64i = !cir.int<u, 64>
+!rec_anon_struct = !cir.record<struct  {!cir.array<!u64i x 4>}>
+module {
+  // expected-error @below {{expected GlobalViewAttr or ConstPtrAttr}}
+  cir.global external @_ZTV1S = #cir.vtable<{#cir.const_array<[#cir.int<1> : !u64i, #cir.int<1> : !u64i, #cir.int<3> : !u64i, #cir.int<4> : !u64i]> : !cir.array<!u64i x 4>}> : !rec_anon_struct {alignment = 8 : i64}
+  cir.func private dso_local @_ZN1S3keyEv(%arg0: !cir.ptr<!rec_S>)
+  cir.func private dso_local @_ZN1S6nonKeyEv(%arg0: !cir.ptr<!rec_S>)
+}
diff --git a/clang/test/CIR/IR/vtable-attr.cir b/clang/test/CIR/IR/vtable-attr.cir
new file mode 100644
index 0000000000000..4826bdcc90953
--- /dev/null
+++ b/clang/test/CIR/IR/vtable-attr.cir
@@ -0,0 +1,12 @@
+// RUN: cir-opt %s | FileCheck %s
+
+!rec_S = !cir.record<struct "S" {!cir.vptr}>
+!u8i = !cir.int<u, 8>
+!rec_anon_struct = !cir.record<struct  {!cir.array<!cir.ptr<!u8i> x 4>}>
+module {
+  cir.global external @_ZTV1S = #cir.vtable<{#cir.const_array<[#cir.ptr<null> : !cir.ptr<!u8i>, #cir.ptr<null> : !cir.ptr<!u8i>, #cir.global_view<@_ZN1S3keyEv> : !cir.ptr<!u8i>, #cir.global_view<@_ZN1S6nonKeyEv> : !cir.ptr<!u8i>]> : !cir.array<!cir.ptr<!u8i> x 4>}> : !rec_anon_struct {alignment = 8 : i64}
+  // CHECK: cir.global external @_ZTV1S = #cir.vtable<{#cir.const_array<[#cir.ptr<null> : !cir.ptr<!u8i>, #cir.ptr<null> : !cir.ptr<!u8i>, #cir.global_view<@_ZN1S3keyEv> : !cir.ptr<!u8i>, #cir.global_view<@_ZN1S6nonKeyEv> : !cir.ptr<!u8i>]> : !cir.array<!cir.ptr<!u8i> x 4>}> : !rec_anon_struct {alignment = 8 : i64}
+
+  cir.func private dso_local @_ZN1S3keyEv(%arg0: !cir.ptr<!rec_S>)
+  cir.func private dso_local @_ZN1S6nonKeyEv(%arg0: !cir.ptr<!rec_S>)
+}

xlauko · 2025-08-20T07:19:08Z

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

+// VTableAttr
+//===----------------------------------------------------------------------===//
+
+def VTableAttr : CIR_Attr<"VTable", "vtable", [TypedAttrInterface]> {


Suggested change

def VTableAttr : CIR_Attr<"VTable", "vtable", [TypedAttrInterface]> {

def CIR_VTableAttr : CIR_Attr<"VTable", "vtable", [TypedAttrInterface]> {

xlauko · 2025-08-20T07:21:52Z

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

+def VTableAttr : CIR_Attr<"VTable", "vtable", [TypedAttrInterface]> {
+  let summary = "Represents a C++ vtable";
+  let description = [{
+    Wraps a #cir.const_record containing vtable data.


I don't get how this wraps record, since it wraps vtable array?

This can potentially wrap a record containing multiple vtable arrays. In the simple case, we create an anonymous record that has a single array element, which looks like this:

cir.global linkonce_odr @_ZTV6Mother = #cir.vtable<{ #cir.const_array<[ #cir.ptr<null> : !cir.ptr<!u8i>, #cir.global_view<@_ZTI6Mother> : !cir.ptr<!u8i>, #cir.global_view<@_ZN6Mother9MotherFooEv> : !cir.ptr<!u8i>, #cir.global_view<@_ZN6Mother10MotherFoo2Ev> : !cir.ptr<!u8i> ]> : !cir.array<!cir.ptr<!u8i> x 4> }> : !rec_anon_struct2 {alignment = 8 : i64 }

But in cases involving multiple inheritence, there can be multiple vtables within the record, like this:

cir.global linkonce_odr @_ZTV5Child = #cir.vtable<{ #cir.const_array<[ #cir.ptr<null> : !cir.ptr<!u8i>, #cir.global_view<@_ZTI5Child> : !cir.ptr<!u8i>, #cir.global_view<@_ZN5Child9MotherFooEv> : !cir.ptr<!u8i>, #cir.global_view<@_ZN6Mother10MotherFoo2Ev> : !cir.ptr<!u8i> ]> : !cir.array<!cir.ptr<!u8i> x 4>, #cir.const_array<[ #cir.ptr<-8 : i64> : !cir.ptr<!u8i>, #cir.global_view<@_ZTI5Child> : !cir.ptr<!u8i>, #cir.global_view<@_ZN6Father9FatherFooEv> : !cir.ptr<!u8i> ]> : !cir.array<!cir.ptr<!u8i> x 3> }> : !rec_anon_struct4 {alignment = 8 : i64}

The index attribute in the address_point selects which of the wrapped vtables is being referenced:

` %6 = cir.vtable.address_point(@_ZTV5Child, address_point = <index = 1, offset = 2>) : !cir.vptr

Ah makes sense, thanks for explanation. With example this will be clearer :)

xlauko · 2025-08-20T07:23:24Z

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

+    ```
+  }];
+
+  // `vtable_data` is a const record with one element, containing an array of


Same here, it is not const_record but ArrayAttr?
Wasn't the intent to say vtable_data is a single element of vtable const record?

As mentioned above, there can be multiple arrays. I'll update this comment to reflect that and add an example with two arrays.

xlauko · 2025-08-20T07:23:39Z

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

+  let parameters = (ins AttributeSelfTypeParameter<"">:$type,
+                        "mlir::ArrayAttr":$vtable_data);


Suggested change

let parameters = (ins AttributeSelfTypeParameter<"">:$type,

"mlir::ArrayAttr":$vtable_data);

let parameters = (ins

AttributeSelfTypeParameter<"">:$type,

"mlir::ArrayAttr":$vtable_data

);

xlauko · 2025-08-20T07:28:03Z

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

+    LogicalResult eltTypeCheck = success();
+    auto arrayElts = mlir::cast<ArrayAttr>(constArrayAttr.getElts());
+    arrayElts.walkImmediateSubElements(
+        [&](Attribute attr) {


Suggested change

[&](Attribute attr) {

[&](mlir::Attribute attr) {

xlauko · 2025-08-20T07:28:10Z

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

+          eltTypeCheck = emitError()
+                         << "expected GlobalViewAttr or ConstPtrAttr";
+        },
+        [&](Type type) {});


Suggested change

[&](Type type) {});

[&](mlir::Type type) {});

xlauko · 2025-08-20T07:37:26Z

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

+  if (sTy.getMembers().empty() || vtableData.empty())
+    return emitError() << "expected record type with one or more subtype";
+
+  for (size_t i = 0; i < sTy.getMembers().size(); ++i) {


There should be only one member, so the loop is a bit misleading here.

Cannot we just assert that size == 1 and that the single element is the expected array?

Maybe it is completely redundant check as cir::ConstRecordAttr::verify checks this?

I thought the same thing when I was moving this over and had changed it in the way you suggest before finding the multi-vtable example (clang/test/CIR/CodeGen/multi-vtable.cpp in the incubator). It didn't occur to me until just now that, like you, I probably thought that because of what the comments in the attribute declaration said.

Could we use a range based for loop here, or if we need the index, use llvm::enumerate instead? We’re currently just using i for indexing

That's a good suggestion. Thanks. It also led me to notice something I had missed.

mmha · 2025-08-20T13:09:39Z

Is this also meant to cover VTTs?

andykaylor · 2025-08-20T17:40:59Z

Is this also meant to cover VTTs?

As we discussed earlier, this isn't used for VTTs. Currently, the incubator emits VTTs as a constant array of global view pointers to vtables. We may want to consider a wrapper attribute similar to this for VTTs.

andykaylor · 2025-08-20T17:55:54Z

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

+def VTableAttr : CIR_Attr<"VTable", "vtable", [TypedAttrInterface]> {
+  let summary = "Represents a C++ vtable";
+  let description = [{
+    Wraps a #cir.const_record containing vtable data.


This can potentially wrap a record containing multiple vtable arrays. In the simple case, we create an anonymous record that has a single array element, which looks like this:

cir.global linkonce_odr @_ZTV6Mother = #cir.vtable<{ #cir.const_array<[ #cir.ptr<null> : !cir.ptr<!u8i>, #cir.global_view<@_ZTI6Mother> : !cir.ptr<!u8i>, #cir.global_view<@_ZN6Mother9MotherFooEv> : !cir.ptr<!u8i>, #cir.global_view<@_ZN6Mother10MotherFoo2Ev> : !cir.ptr<!u8i> ]> : !cir.array<!cir.ptr<!u8i> x 4> }> : !rec_anon_struct2 {alignment = 8 : i64 }

But in cases involving multiple inheritence, there can be multiple vtables within the record, like this:

cir.global linkonce_odr @_ZTV5Child = #cir.vtable<{ #cir.const_array<[ #cir.ptr<null> : !cir.ptr<!u8i>, #cir.global_view<@_ZTI5Child> : !cir.ptr<!u8i>, #cir.global_view<@_ZN5Child9MotherFooEv> : !cir.ptr<!u8i>, #cir.global_view<@_ZN6Mother10MotherFoo2Ev> : !cir.ptr<!u8i> ]> : !cir.array<!cir.ptr<!u8i> x 4>, #cir.const_array<[ #cir.ptr<-8 : i64> : !cir.ptr<!u8i>, #cir.global_view<@_ZTI5Child> : !cir.ptr<!u8i>, #cir.global_view<@_ZN6Father9FatherFooEv> : !cir.ptr<!u8i> ]> : !cir.array<!cir.ptr<!u8i> x 3> }> : !rec_anon_struct4 {alignment = 8 : i64}

The index attribute in the address_point selects which of the wrapped vtables is being referenced:

` %6 = cir.vtable.address_point(@_ZTV5Child, address_point = <index = 1, offset = 2>) : !cir.vptr

andykaylor · 2025-08-20T17:57:41Z

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

+
+    Example:
+    ```
+    cir.global linkonce_odr @_ZTV1B = #cir.vtable<<


There seem to be extra brackets in this example, which may be making it harder to understand.

andykaylor · 2025-08-20T17:58:44Z

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

+    ```
+  }];
+
+  // `vtable_data` is a const record with one element, containing an array of


As mentioned above, there can be multiple arrays. I'll update this comment to reflect that and add an example with two arrays.

andykaylor · 2025-08-20T18:01:31Z

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

+  if (sTy.getMembers().empty() || vtableData.empty())
+    return emitError() << "expected record type with one or more subtype";
+
+  for (size_t i = 0; i < sTy.getMembers().size(); ++i) {


I thought the same thing when I was moving this over and had changed it in the way you suggest before finding the multi-vtable example (clang/test/CIR/CodeGen/multi-vtable.cpp in the incubator). It didn't occur to me until just now that, like you, I probably thought that because of what the comments in the attribute declaration said.

bcardosolopes

LGTM, minor suggestion

bcardosolopes · 2025-08-20T22:51:14Z

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

+  // vtable information.
+  let parameters = (ins
+    AttributeSelfTypeParameter<"">:$type,
+    "mlir::ArrayAttr":$vtable_data


Should we just call this one data instead of vtable_data? To use the param you need the casted attribute anyways, so repeating the name might not help much here.

[CIR] Add CIR vtable attribute

f5e0612

This adds the #cir.vtable attribute definition and verification. Generation of the vtable will be implemented in a later change.

andykaylor requested review from Andres-Salamanca, bcardosolopes, erichkeane, lanza, mmha and xlauko August 19, 2025 19:39

llvmbot added clang Clang issues not falling into any other category ClangIR Anything related to the ClangIR project labels Aug 19, 2025

xlauko reviewed Aug 20, 2025

View reviewed changes

andykaylor commented Aug 20, 2025

View reviewed changes

andykaylor added 3 commits August 20, 2025 13:04

Address review feedback

d37efd2

Use range for vtable data verification

98c808f

Add multi-vtable test

32180c9

bcardosolopes approved these changes Aug 20, 2025

View reviewed changes

One more test case

1736a32

Andres-Salamanca approved these changes Aug 20, 2025

View reviewed changes

mmha approved these changes Aug 21, 2025

View reviewed changes

Rename vtable_data to data

6f96418

andykaylor merged commit c5466c6 into llvm:main Aug 21, 2025
9 checks passed

andykaylor deleted the cir-vtable-attr branch August 21, 2025 16:52

andykaylor mentioned this pull request Sep 23, 2025

[CIR] Upstream support for virtual functions #143787

Closed

	def VTableAttr : CIR_Attr<"VTable", "vtable", [TypedAttrInterface]> {
	def CIR_VTableAttr : CIR_Attr<"VTable", "vtable", [TypedAttrInterface]> {

		let parameters = (ins AttributeSelfTypeParameter<"">:$type,
		"mlir::ArrayAttr":$vtable_data);

[CIR] Add CIR vtable attribute #154415

[CIR] Add CIR vtable attribute #154415

Uh oh!

Conversation

andykaylor commented Aug 19, 2025

Uh oh!

llvmbot commented Aug 19, 2025

Uh oh!

llvmbot commented Aug 19, 2025

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

mmha commented Aug 20, 2025

Uh oh!

andykaylor commented Aug 20, 2025

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

bcardosolopes left a comment

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

6 participants