[CIR] Add support for dynamic cast to void #162905

andykaylor · 2025-10-10T19:27:32Z

This adds the support for dynamic cast to void in the Itanium ABI.

llvmbot · 2025-10-10T19:28:08Z

@llvm/pr-subscribers-clang

Author: Andy Kaylor (andykaylor)

Changes

This adds the support for dynamic cast to void in the Itanium ABI.

Full diff: https://github.com/llvm/llvm-project/pull/162905.diff

5 Files Affected:

(modified) clang/include/clang/CIR/Dialect/Builder/CIRBaseBuilder.h (+8)
(modified) clang/lib/CIR/CodeGen/CIRGenBuilder.h (+10)
(modified) clang/lib/CIR/CodeGen/CIRGenItaniumCXXABI.cpp (+11-4)
(modified) clang/lib/CIR/Dialect/Transforms/LoweringPrepareItaniumCXXABI.cpp (+47-1)
(modified) clang/test/CIR/CodeGen/dynamic-cast.cpp (+56)

diff --git a/clang/include/clang/CIR/Dialect/Builder/CIRBaseBuilder.h b/clang/include/clang/CIR/Dialect/Builder/CIRBaseBuilder.h
index b4c24d7e4a8aa..3ac8987864168 100644
--- a/clang/include/clang/CIR/Dialect/Builder/CIRBaseBuilder.h
+++ b/clang/include/clang/CIR/Dialect/Builder/CIRBaseBuilder.h
@@ -127,6 +127,14 @@ class CIRBaseBuilderTy : public mlir::OpBuilder {
   cir::BoolType getBoolTy() { return cir::BoolType::get(getContext()); }
   cir::VoidType getVoidTy() { return cir::VoidType::get(getContext()); }
 
+  cir::IntType getUIntNTy(int n) {
+    return cir::IntType::get(getContext(), n, false);
+  }
+
+  cir::IntType getSIntNTy(int n) {
+    return cir::IntType::get(getContext(), n, true);
+  }
+
   cir::PointerType getPointerTo(mlir::Type ty) {
     return cir::PointerType::get(ty);
   }
diff --git a/clang/lib/CIR/CodeGen/CIRGenBuilder.h b/clang/lib/CIR/CodeGen/CIRGenBuilder.h
index a6f10e6bb9e9c..7eed0c4c1a243 100644
--- a/clang/lib/CIR/CodeGen/CIRGenBuilder.h
+++ b/clang/lib/CIR/CodeGen/CIRGenBuilder.h
@@ -380,6 +380,16 @@ class CIRGenBuilderTy : public cir::CIRBaseBuilderTy {
                                       /*relative_layout=*/false);
   }
 
+  mlir::Value createDynCastToVoid(mlir::Location loc, mlir::Value src,
+                                  bool vtableUseRelativeLayout) {
+    // TODO(cir): consider address space here.
+    assert(!cir::MissingFeatures::addressSpace());
+    cir::PointerType destTy = getVoidPtrTy();
+    return cir::DynamicCastOp::create(
+        *this, loc, destTy, cir::DynamicCastKind::Ptr, src,
+        cir::DynamicCastInfoAttr{}, vtableUseRelativeLayout);
+  }
+
   Address createBaseClassAddr(mlir::Location loc, Address addr,
                               mlir::Type destType, unsigned offset,
                               bool assumeNotNull) {
diff --git a/clang/lib/CIR/CodeGen/CIRGenItaniumCXXABI.cpp b/clang/lib/CIR/CodeGen/CIRGenItaniumCXXABI.cpp
index 9e490c6d054a4..6e459edc951ab 100644
--- a/clang/lib/CIR/CodeGen/CIRGenItaniumCXXABI.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenItaniumCXXABI.cpp
@@ -1925,6 +1925,15 @@ static cir::FuncOp getItaniumDynamicCastFn(CIRGenFunction &cgf) {
   return cgf.cgm.createRuntimeFunction(FTy, "__dynamic_cast");
 }
 
+static Address emitDynamicCastToVoid(CIRGenFunction &cgf, mlir::Location loc,
+                                     QualType srcRecordTy, Address src) {
+  bool vtableUsesRelativeLayout =
+      cgf.cgm.getItaniumVTableContext().isRelativeLayout();
+  mlir::Value ptr = cgf.getBuilder().createDynCastToVoid(
+      loc, src.getPointer(), vtableUsesRelativeLayout);
+  return Address{ptr, src.getAlignment()};
+}
+
 static cir::DynamicCastInfoAttr emitDynamicCastInfo(CIRGenFunction &cgf,
                                                     mlir::Location loc,
                                                     QualType srcRecordTy,
@@ -1959,10 +1968,8 @@ mlir::Value CIRGenItaniumCXXABI::emitDynamicCast(CIRGenFunction &cgf,
   bool isCastToVoid = destRecordTy.isNull();
   assert((!isCastToVoid || !isRefCast) && "cannot cast to void reference");
 
-  if (isCastToVoid) {
-    cgm.errorNYI(loc, "emitDynamicCastToVoid");
-    return {};
-  }
+  if (isCastToVoid)
+    return emitDynamicCastToVoid(cgf, loc, srcRecordTy, src).getPointer();
 
   // If the destination is effectively final, the cast succeeds if and only
   // if the dynamic type of the pointer is exactly the destination type.
diff --git a/clang/lib/CIR/Dialect/Transforms/LoweringPrepareItaniumCXXABI.cpp b/clang/lib/CIR/Dialect/Transforms/LoweringPrepareItaniumCXXABI.cpp
index 7d3c711251b9f..11ce2a81e7f39 100644
--- a/clang/lib/CIR/Dialect/Transforms/LoweringPrepareItaniumCXXABI.cpp
+++ b/clang/lib/CIR/Dialect/Transforms/LoweringPrepareItaniumCXXABI.cpp
@@ -92,7 +92,53 @@ static mlir::Value
 buildDynamicCastToVoidAfterNullCheck(cir::CIRBaseBuilderTy &builder,
                                      clang::ASTContext &astCtx,
                                      cir::DynamicCastOp op) {
-  llvm_unreachable("dynamic cast to void is NYI");
+  mlir::Location loc = op.getLoc();
+  bool vtableUsesRelativeLayout = op.getRelativeLayout();
+
+  // TODO(cir): consider address space in this function.
+  assert(!cir::MissingFeatures::addressSpace());
+
+  mlir::Type vtableElemTy;
+  uint64_t vtableElemAlign;
+  if (vtableUsesRelativeLayout) {
+    vtableElemTy = builder.getSIntNTy(32);
+    vtableElemAlign = 4;
+  } else {
+    const auto &targetInfo = astCtx.getTargetInfo();
+    auto ptrdiffTy = targetInfo.getPtrDiffType(clang::LangAS::Default);
+    bool ptrdiffTyIsSigned = clang::TargetInfo::isTypeSigned(ptrdiffTy);
+    uint64_t ptrdiffTyWidth = targetInfo.getTypeWidth(ptrdiffTy);
+
+    vtableElemTy = cir::IntType::get(builder.getContext(), ptrdiffTyWidth,
+                                     ptrdiffTyIsSigned);
+    vtableElemAlign =
+        llvm::divideCeil(targetInfo.getPointerAlign(clang::LangAS::Default), 8);
+  }
+
+  // Access vtable to get the offset from the given object to its containing
+  // complete object.
+  // TODO: Add a specialized operation to get the object offset?
+  auto vptrTy = cir::VPtrType::get(builder.getContext());
+  cir::PointerType vptrPtrTy = builder.getPointerTo(vptrTy);
+  auto vptrPtr =
+      cir::VTableGetVPtrOp::create(builder, loc, vptrPtrTy, op.getSrc());
+  mlir::Value vptr = builder.createLoad(loc, vptrPtr);
+  mlir::Value elementPtr =
+      builder.createBitcast(vptr, builder.getPointerTo(vtableElemTy));
+  mlir::Value minusTwo = builder.getSignedInt(loc, -2, 64);
+  auto offsetToTopSlotPtr = cir::PtrStrideOp::create(
+      builder, loc, builder.getPointerTo(vtableElemTy), elementPtr, minusTwo);
+  mlir::Value offsetToTop =
+      builder.createAlignedLoad(loc, offsetToTopSlotPtr, vtableElemAlign);
+
+  // Add the offset to the given pointer to get the cast result.
+  // Cast the input pointer to a uint8_t* to allow pointer arithmetic.
+  cir::PointerType u8PtrTy = builder.getPointerTo(builder.getUIntNTy(8));
+  mlir::Value srcBytePtr = builder.createBitcast(op.getSrc(), u8PtrTy);
+  auto dstBytePtr =
+      cir::PtrStrideOp::create(builder, loc, u8PtrTy, srcBytePtr, offsetToTop);
+  // Cast the result to a void*.
+  return builder.createBitcast(dstBytePtr, builder.getVoidPtrTy());
 }
 
 mlir::Value
diff --git a/clang/test/CIR/CodeGen/dynamic-cast.cpp b/clang/test/CIR/CodeGen/dynamic-cast.cpp
index b4938402f0256..5d010d20bb9f1 100644
--- a/clang/test/CIR/CodeGen/dynamic-cast.cpp
+++ b/clang/test/CIR/CodeGen/dynamic-cast.cpp
@@ -101,3 +101,59 @@ Derived &ref_cast(Base &b) {
 // OGCG:   br i1 %[[IS_NULL]], label %[[BAD_CAST:.*]], label %[[DONE:.*]]
 // OGCG: [[BAD_CAST]]:
 // OGCG:   call void @__cxa_bad_cast()
+
+void *ptr_cast_to_complete(Base *ptr) {
+  return dynamic_cast<void *>(ptr);
+}
+
+// CIR-BEFORE: cir.func dso_local @_Z20ptr_cast_to_completeP4Base
+// CIR-BEFORE:   %{{.+}} = cir.dyn_cast ptr %{{.+}} : !cir.ptr<!rec_Base> -> !cir.ptr<!void>
+// CIR-BEFORE: }
+
+//      CIR-AFTER: cir.func dso_local @_Z20ptr_cast_to_completeP4Base
+//      CIR-AFTER:   %[[SRC:.*]] = cir.load{{.*}} %{{.+}} : !cir.ptr<!cir.ptr<!rec_Base>>, !cir.ptr<!rec_Base>
+// CIR-AFTER-NEXT:   %[[SRC_IS_NOT_NULL:.*]] = cir.cast ptr_to_bool %[[SRC]] : !cir.ptr<!rec_Base> -> !cir.bool
+// CIR-AFTER-NEXT:   %{{.+}} = cir.ternary(%[[SRC_IS_NOT_NULL]], true {
+// CIR-AFTER-NEXT:     %[[VPTR_PTR:.*]] = cir.vtable.get_vptr %[[SRC]] : !cir.ptr<!rec_Base> -> !cir.ptr<!cir.vptr>
+// CIR-AFTER-NEXT:     %[[VPTR:.*]] = cir.load %[[VPTR_PTR]] : !cir.ptr<!cir.vptr>, !cir.vptr
+// CIR-AFTER-NEXT:     %[[ELEM_PTR:.*]] = cir.cast bitcast %[[VPTR]] : !cir.vptr -> !cir.ptr<!s64i>
+// CIR-AFTER-NEXT:     %[[MINUS_TWO:.*]] = cir.const #cir.int<-2> : !s64i
+// CIR-AFTER-NEXT:     %[[BASE_OFFSET_PTR:.*]] = cir.ptr_stride %[[ELEM_PTR]], %[[MINUS_TWO]] : (!cir.ptr<!s64i>, !s64i) -> !cir.ptr<!s64i>
+// CIR-AFTER-NEXT:     %[[BASE_OFFSET:.*]] = cir.load{{.*}} %[[BASE_OFFSET_PTR]] : !cir.ptr<!s64i>, !s64i
+// CIR-AFTER-NEXT:     %[[SRC_BYTES_PTR:.*]] = cir.cast bitcast %[[SRC]] : !cir.ptr<!rec_Base> -> !cir.ptr<!u8i>
+// CIR-AFTER-NEXT:     %[[DST_BYTES_PTR:.*]] = cir.ptr_stride %[[SRC_BYTES_PTR]], %[[BASE_OFFSET]] : (!cir.ptr<!u8i>, !s64i) -> !cir.ptr<!u8i>
+// CIR-AFTER-NEXT:     %[[CASTED_PTR:.*]] = cir.cast bitcast %[[DST_BYTES_PTR]] : !cir.ptr<!u8i> -> !cir.ptr<!void>
+// CIR-AFTER-NEXT:     cir.yield %[[CASTED_PTR]] : !cir.ptr<!void>
+// CIR-AFTER-NEXT:   }, false {
+// CIR-AFTER-NEXT:     %[[NULL_PTR:.*]] = cir.const #cir.ptr<null> : !cir.ptr<!void>
+// CIR-AFTER-NEXT:     cir.yield %[[NULL_PTR]] : !cir.ptr<!void>
+// CIR-AFTER-NEXT:   }) : (!cir.bool) -> !cir.ptr<!void>
+//      CIR-AFTER: }
+
+// LLVM: define {{.*}} @_Z20ptr_cast_to_completeP4Base
+// LLVM:   %[[IS_NOT_NULL:.*]] = icmp ne ptr %[[PTR:.*]], null
+// LLVM:   br i1 %[[IS_NOT_NULL]], label %[[NOT_NULL:.*]], label %[[NULL:.*]]
+// LLVM: [[NOT_NULL]]:
+// LLVM:   %[[VPTR:.*]] = load ptr, ptr %[[PTR]]
+// LLVM:   %[[BASE_OFFSET_PTR:.*]] = getelementptr i64, ptr %7, i64 -2
+// LLVM:   %[[BASE_OFFSET:.*]] = load i64, ptr %[[BASE_OFFSET_PTR]]
+// LLVM:   %[[RESULT:.*]] = getelementptr i8, ptr %[[PTR]], i64 %[[BASE_OFFSET]]
+// LLVM:   br label %[[DONE:.*]]
+// LLVM: [[NULL]]:
+// LLVM:   br label %[[DONE]]
+// LLVM: [[DONE]]:
+// LLVM:   %[[RET:.*]] = phi ptr [ null, %[[NULL]] ], [ %[[RESULT]], %[[NOT_NULL]] ]
+
+// OGCG: define {{.*}} @_Z20ptr_cast_to_completeP4Base
+// OGCG:   %[[IS_NULL:.*]] = icmp eq ptr %[[PTR:.*]], null
+// OGCG:   br i1 %[[IS_NULL]], label %[[NULL:.*]], label %[[NOT_NULL:.*]]
+// OGCG: [[NOT_NULL]]:
+// OGCG:   %[[VPTR:.*]] = load ptr, ptr %[[PTR]]
+// OGCG:   %[[BASE_OFFSET_PTR:.*]] = getelementptr inbounds i64, ptr %[[VPTR]], i64 -2
+// OGCG:   %[[BASE_OFFSET:.*]] = load i64, ptr %[[BASE_OFFSET_PTR]]
+// OGCG:   %[[RESULT:.*]] = getelementptr inbounds i8, ptr %[[PTR]], i64 %[[BASE_OFFSET]]
+// OGCG:   br label %[[DONE:.*]]
+// OGCG: [[NULL]]:
+// OGCG:   br label %[[DONE]]
+// OGCG: [[DONE]]:
+// OGCG:   %[[RET:.*]] = phi ptr [ %[[RESULT]], %[[NOT_NULL]] ], [ null, %[[NULL]] ]

llvmbot · 2025-10-10T19:28:09Z

@llvm/pr-subscribers-clangir

Author: Andy Kaylor (andykaylor)

Changes

This adds the support for dynamic cast to void in the Itanium ABI.

Full diff: https://github.com/llvm/llvm-project/pull/162905.diff

5 Files Affected:

(modified) clang/include/clang/CIR/Dialect/Builder/CIRBaseBuilder.h (+8)
(modified) clang/lib/CIR/CodeGen/CIRGenBuilder.h (+10)
(modified) clang/lib/CIR/CodeGen/CIRGenItaniumCXXABI.cpp (+11-4)
(modified) clang/lib/CIR/Dialect/Transforms/LoweringPrepareItaniumCXXABI.cpp (+47-1)
(modified) clang/test/CIR/CodeGen/dynamic-cast.cpp (+56)

diff --git a/clang/include/clang/CIR/Dialect/Builder/CIRBaseBuilder.h b/clang/include/clang/CIR/Dialect/Builder/CIRBaseBuilder.h
index b4c24d7e4a8aa..3ac8987864168 100644
--- a/clang/include/clang/CIR/Dialect/Builder/CIRBaseBuilder.h
+++ b/clang/include/clang/CIR/Dialect/Builder/CIRBaseBuilder.h
@@ -127,6 +127,14 @@ class CIRBaseBuilderTy : public mlir::OpBuilder {
   cir::BoolType getBoolTy() { return cir::BoolType::get(getContext()); }
   cir::VoidType getVoidTy() { return cir::VoidType::get(getContext()); }
 
+  cir::IntType getUIntNTy(int n) {
+    return cir::IntType::get(getContext(), n, false);
+  }
+
+  cir::IntType getSIntNTy(int n) {
+    return cir::IntType::get(getContext(), n, true);
+  }
+
   cir::PointerType getPointerTo(mlir::Type ty) {
     return cir::PointerType::get(ty);
   }
diff --git a/clang/lib/CIR/CodeGen/CIRGenBuilder.h b/clang/lib/CIR/CodeGen/CIRGenBuilder.h
index a6f10e6bb9e9c..7eed0c4c1a243 100644
--- a/clang/lib/CIR/CodeGen/CIRGenBuilder.h
+++ b/clang/lib/CIR/CodeGen/CIRGenBuilder.h
@@ -380,6 +380,16 @@ class CIRGenBuilderTy : public cir::CIRBaseBuilderTy {
                                       /*relative_layout=*/false);
   }
 
+  mlir::Value createDynCastToVoid(mlir::Location loc, mlir::Value src,
+                                  bool vtableUseRelativeLayout) {
+    // TODO(cir): consider address space here.
+    assert(!cir::MissingFeatures::addressSpace());
+    cir::PointerType destTy = getVoidPtrTy();
+    return cir::DynamicCastOp::create(
+        *this, loc, destTy, cir::DynamicCastKind::Ptr, src,
+        cir::DynamicCastInfoAttr{}, vtableUseRelativeLayout);
+  }
+
   Address createBaseClassAddr(mlir::Location loc, Address addr,
                               mlir::Type destType, unsigned offset,
                               bool assumeNotNull) {
diff --git a/clang/lib/CIR/CodeGen/CIRGenItaniumCXXABI.cpp b/clang/lib/CIR/CodeGen/CIRGenItaniumCXXABI.cpp
index 9e490c6d054a4..6e459edc951ab 100644
--- a/clang/lib/CIR/CodeGen/CIRGenItaniumCXXABI.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenItaniumCXXABI.cpp
@@ -1925,6 +1925,15 @@ static cir::FuncOp getItaniumDynamicCastFn(CIRGenFunction &cgf) {
   return cgf.cgm.createRuntimeFunction(FTy, "__dynamic_cast");
 }
 
+static Address emitDynamicCastToVoid(CIRGenFunction &cgf, mlir::Location loc,
+                                     QualType srcRecordTy, Address src) {
+  bool vtableUsesRelativeLayout =
+      cgf.cgm.getItaniumVTableContext().isRelativeLayout();
+  mlir::Value ptr = cgf.getBuilder().createDynCastToVoid(
+      loc, src.getPointer(), vtableUsesRelativeLayout);
+  return Address{ptr, src.getAlignment()};
+}
+
 static cir::DynamicCastInfoAttr emitDynamicCastInfo(CIRGenFunction &cgf,
                                                     mlir::Location loc,
                                                     QualType srcRecordTy,
@@ -1959,10 +1968,8 @@ mlir::Value CIRGenItaniumCXXABI::emitDynamicCast(CIRGenFunction &cgf,
   bool isCastToVoid = destRecordTy.isNull();
   assert((!isCastToVoid || !isRefCast) && "cannot cast to void reference");
 
-  if (isCastToVoid) {
-    cgm.errorNYI(loc, "emitDynamicCastToVoid");
-    return {};
-  }
+  if (isCastToVoid)
+    return emitDynamicCastToVoid(cgf, loc, srcRecordTy, src).getPointer();
 
   // If the destination is effectively final, the cast succeeds if and only
   // if the dynamic type of the pointer is exactly the destination type.
diff --git a/clang/lib/CIR/Dialect/Transforms/LoweringPrepareItaniumCXXABI.cpp b/clang/lib/CIR/Dialect/Transforms/LoweringPrepareItaniumCXXABI.cpp
index 7d3c711251b9f..11ce2a81e7f39 100644
--- a/clang/lib/CIR/Dialect/Transforms/LoweringPrepareItaniumCXXABI.cpp
+++ b/clang/lib/CIR/Dialect/Transforms/LoweringPrepareItaniumCXXABI.cpp
@@ -92,7 +92,53 @@ static mlir::Value
 buildDynamicCastToVoidAfterNullCheck(cir::CIRBaseBuilderTy &builder,
                                      clang::ASTContext &astCtx,
                                      cir::DynamicCastOp op) {
-  llvm_unreachable("dynamic cast to void is NYI");
+  mlir::Location loc = op.getLoc();
+  bool vtableUsesRelativeLayout = op.getRelativeLayout();
+
+  // TODO(cir): consider address space in this function.
+  assert(!cir::MissingFeatures::addressSpace());
+
+  mlir::Type vtableElemTy;
+  uint64_t vtableElemAlign;
+  if (vtableUsesRelativeLayout) {
+    vtableElemTy = builder.getSIntNTy(32);
+    vtableElemAlign = 4;
+  } else {
+    const auto &targetInfo = astCtx.getTargetInfo();
+    auto ptrdiffTy = targetInfo.getPtrDiffType(clang::LangAS::Default);
+    bool ptrdiffTyIsSigned = clang::TargetInfo::isTypeSigned(ptrdiffTy);
+    uint64_t ptrdiffTyWidth = targetInfo.getTypeWidth(ptrdiffTy);
+
+    vtableElemTy = cir::IntType::get(builder.getContext(), ptrdiffTyWidth,
+                                     ptrdiffTyIsSigned);
+    vtableElemAlign =
+        llvm::divideCeil(targetInfo.getPointerAlign(clang::LangAS::Default), 8);
+  }
+
+  // Access vtable to get the offset from the given object to its containing
+  // complete object.
+  // TODO: Add a specialized operation to get the object offset?
+  auto vptrTy = cir::VPtrType::get(builder.getContext());
+  cir::PointerType vptrPtrTy = builder.getPointerTo(vptrTy);
+  auto vptrPtr =
+      cir::VTableGetVPtrOp::create(builder, loc, vptrPtrTy, op.getSrc());
+  mlir::Value vptr = builder.createLoad(loc, vptrPtr);
+  mlir::Value elementPtr =
+      builder.createBitcast(vptr, builder.getPointerTo(vtableElemTy));
+  mlir::Value minusTwo = builder.getSignedInt(loc, -2, 64);
+  auto offsetToTopSlotPtr = cir::PtrStrideOp::create(
+      builder, loc, builder.getPointerTo(vtableElemTy), elementPtr, minusTwo);
+  mlir::Value offsetToTop =
+      builder.createAlignedLoad(loc, offsetToTopSlotPtr, vtableElemAlign);
+
+  // Add the offset to the given pointer to get the cast result.
+  // Cast the input pointer to a uint8_t* to allow pointer arithmetic.
+  cir::PointerType u8PtrTy = builder.getPointerTo(builder.getUIntNTy(8));
+  mlir::Value srcBytePtr = builder.createBitcast(op.getSrc(), u8PtrTy);
+  auto dstBytePtr =
+      cir::PtrStrideOp::create(builder, loc, u8PtrTy, srcBytePtr, offsetToTop);
+  // Cast the result to a void*.
+  return builder.createBitcast(dstBytePtr, builder.getVoidPtrTy());
 }
 
 mlir::Value
diff --git a/clang/test/CIR/CodeGen/dynamic-cast.cpp b/clang/test/CIR/CodeGen/dynamic-cast.cpp
index b4938402f0256..5d010d20bb9f1 100644
--- a/clang/test/CIR/CodeGen/dynamic-cast.cpp
+++ b/clang/test/CIR/CodeGen/dynamic-cast.cpp
@@ -101,3 +101,59 @@ Derived &ref_cast(Base &b) {
 // OGCG:   br i1 %[[IS_NULL]], label %[[BAD_CAST:.*]], label %[[DONE:.*]]
 // OGCG: [[BAD_CAST]]:
 // OGCG:   call void @__cxa_bad_cast()
+
+void *ptr_cast_to_complete(Base *ptr) {
+  return dynamic_cast<void *>(ptr);
+}
+
+// CIR-BEFORE: cir.func dso_local @_Z20ptr_cast_to_completeP4Base
+// CIR-BEFORE:   %{{.+}} = cir.dyn_cast ptr %{{.+}} : !cir.ptr<!rec_Base> -> !cir.ptr<!void>
+// CIR-BEFORE: }
+
+//      CIR-AFTER: cir.func dso_local @_Z20ptr_cast_to_completeP4Base
+//      CIR-AFTER:   %[[SRC:.*]] = cir.load{{.*}} %{{.+}} : !cir.ptr<!cir.ptr<!rec_Base>>, !cir.ptr<!rec_Base>
+// CIR-AFTER-NEXT:   %[[SRC_IS_NOT_NULL:.*]] = cir.cast ptr_to_bool %[[SRC]] : !cir.ptr<!rec_Base> -> !cir.bool
+// CIR-AFTER-NEXT:   %{{.+}} = cir.ternary(%[[SRC_IS_NOT_NULL]], true {
+// CIR-AFTER-NEXT:     %[[VPTR_PTR:.*]] = cir.vtable.get_vptr %[[SRC]] : !cir.ptr<!rec_Base> -> !cir.ptr<!cir.vptr>
+// CIR-AFTER-NEXT:     %[[VPTR:.*]] = cir.load %[[VPTR_PTR]] : !cir.ptr<!cir.vptr>, !cir.vptr
+// CIR-AFTER-NEXT:     %[[ELEM_PTR:.*]] = cir.cast bitcast %[[VPTR]] : !cir.vptr -> !cir.ptr<!s64i>
+// CIR-AFTER-NEXT:     %[[MINUS_TWO:.*]] = cir.const #cir.int<-2> : !s64i
+// CIR-AFTER-NEXT:     %[[BASE_OFFSET_PTR:.*]] = cir.ptr_stride %[[ELEM_PTR]], %[[MINUS_TWO]] : (!cir.ptr<!s64i>, !s64i) -> !cir.ptr<!s64i>
+// CIR-AFTER-NEXT:     %[[BASE_OFFSET:.*]] = cir.load{{.*}} %[[BASE_OFFSET_PTR]] : !cir.ptr<!s64i>, !s64i
+// CIR-AFTER-NEXT:     %[[SRC_BYTES_PTR:.*]] = cir.cast bitcast %[[SRC]] : !cir.ptr<!rec_Base> -> !cir.ptr<!u8i>
+// CIR-AFTER-NEXT:     %[[DST_BYTES_PTR:.*]] = cir.ptr_stride %[[SRC_BYTES_PTR]], %[[BASE_OFFSET]] : (!cir.ptr<!u8i>, !s64i) -> !cir.ptr<!u8i>
+// CIR-AFTER-NEXT:     %[[CASTED_PTR:.*]] = cir.cast bitcast %[[DST_BYTES_PTR]] : !cir.ptr<!u8i> -> !cir.ptr<!void>
+// CIR-AFTER-NEXT:     cir.yield %[[CASTED_PTR]] : !cir.ptr<!void>
+// CIR-AFTER-NEXT:   }, false {
+// CIR-AFTER-NEXT:     %[[NULL_PTR:.*]] = cir.const #cir.ptr<null> : !cir.ptr<!void>
+// CIR-AFTER-NEXT:     cir.yield %[[NULL_PTR]] : !cir.ptr<!void>
+// CIR-AFTER-NEXT:   }) : (!cir.bool) -> !cir.ptr<!void>
+//      CIR-AFTER: }
+
+// LLVM: define {{.*}} @_Z20ptr_cast_to_completeP4Base
+// LLVM:   %[[IS_NOT_NULL:.*]] = icmp ne ptr %[[PTR:.*]], null
+// LLVM:   br i1 %[[IS_NOT_NULL]], label %[[NOT_NULL:.*]], label %[[NULL:.*]]
+// LLVM: [[NOT_NULL]]:
+// LLVM:   %[[VPTR:.*]] = load ptr, ptr %[[PTR]]
+// LLVM:   %[[BASE_OFFSET_PTR:.*]] = getelementptr i64, ptr %7, i64 -2
+// LLVM:   %[[BASE_OFFSET:.*]] = load i64, ptr %[[BASE_OFFSET_PTR]]
+// LLVM:   %[[RESULT:.*]] = getelementptr i8, ptr %[[PTR]], i64 %[[BASE_OFFSET]]
+// LLVM:   br label %[[DONE:.*]]
+// LLVM: [[NULL]]:
+// LLVM:   br label %[[DONE]]
+// LLVM: [[DONE]]:
+// LLVM:   %[[RET:.*]] = phi ptr [ null, %[[NULL]] ], [ %[[RESULT]], %[[NOT_NULL]] ]
+
+// OGCG: define {{.*}} @_Z20ptr_cast_to_completeP4Base
+// OGCG:   %[[IS_NULL:.*]] = icmp eq ptr %[[PTR:.*]], null
+// OGCG:   br i1 %[[IS_NULL]], label %[[NULL:.*]], label %[[NOT_NULL:.*]]
+// OGCG: [[NOT_NULL]]:
+// OGCG:   %[[VPTR:.*]] = load ptr, ptr %[[PTR]]
+// OGCG:   %[[BASE_OFFSET_PTR:.*]] = getelementptr inbounds i64, ptr %[[VPTR]], i64 -2
+// OGCG:   %[[BASE_OFFSET:.*]] = load i64, ptr %[[BASE_OFFSET_PTR]]
+// OGCG:   %[[RESULT:.*]] = getelementptr inbounds i8, ptr %[[PTR]], i64 %[[BASE_OFFSET]]
+// OGCG:   br label %[[DONE:.*]]
+// OGCG: [[NULL]]:
+// OGCG:   br label %[[DONE]]
+// OGCG: [[DONE]]:
+// OGCG:   %[[RET:.*]] = phi ptr [ %[[RESULT]], %[[NOT_NULL]] ], [ null, %[[NULL]] ]

[CIR] Add support for dynamic cast to void

943f92e

This adds the support for dynamic cast to void in the Itanium ABI.

andykaylor requested review from bcardosolopes, erichkeane, lanza, mmha and xlauko October 10, 2025 19:27

llvmbot added clang Clang issues not falling into any other category ClangIR Anything related to the ClangIR project labels Oct 10, 2025

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[CIR] Add support for dynamic cast to void #162905

[CIR] Add support for dynamic cast to void #162905

andykaylor commented Oct 10, 2025

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llvmbot commented Oct 10, 2025

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llvmbot commented Oct 10, 2025

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[CIR] Add support for dynamic cast to void #162905

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[CIR] Add support for dynamic cast to void #162905

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andykaylor commented Oct 10, 2025

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llvmbot commented Oct 10, 2025

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llvmbot commented Oct 10, 2025

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