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[CIR] Check for null source point before exact dynamic cast #1953

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Oct 23, 2025
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[CIR] Check for null source point before exact dynamic cast #1953

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22 changes: 21 additions & 1 deletion clang/lib/CIR/CodeGen/CIRGenItaniumCXXABI.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2726,9 +2726,29 @@ mlir::Value CIRGenItaniumCXXABI::emitDynamicCast(CIRGenFunction &CGF,
// If the destination is effectively final, the cast succeeds if and only
// if the dynamic type of the pointer is exactly the destination type.
if (DestRecordTy->getAsCXXRecordDecl()->isEffectivelyFinal() &&
CGF.CGM.getCodeGenOpts().OptimizationLevel > 0)
CGF.CGM.getCodeGenOpts().OptimizationLevel > 0) {
CIRGenBuilderTy &builder = CGF.getBuilder();
// If this isn't a reference cast, check the pointer to see if it's null.
if (!isRefCast) {
mlir::Value srcPtrIsNull = builder.createPtrIsNull(Src.getPointer());
return cir::TernaryOp::create(
builder, Loc, srcPtrIsNull,
[&](mlir::OpBuilder, mlir::Location) {
builder.createYield(
Loc, builder.getNullPtr(DestCIRTy, Loc).getResult());
},
[&](mlir::OpBuilder &, mlir::Location) {
mlir::Value exactCast = emitExactDynamicCast(
*this, CGF, Loc, SrcRecordTy, DestRecordTy, DestCIRTy,
isRefCast, Src);
builder.createYield(Loc, exactCast);
})
.getResult();
}

return emitExactDynamicCast(*this, CGF, Loc, SrcRecordTy, DestRecordTy,
DestCIRTy, isRefCast, Src);
}

auto castInfo = emitDynamicCastInfo(CGF, Loc, SrcRecordTy, DestRecordTy);
return CGF.getBuilder().createDynCast(Loc, Src.getPointer(), DestCIRTy,
Expand Down
71 changes: 57 additions & 14 deletions clang/test/CIR/CodeGen/dynamic-cast-exact.cpp
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Original file line number Diff line number Diff line change
@@ -1,7 +1,9 @@
// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -std=c++20 -O1 -fclangir -clangir-disable-passes -emit-cir -o %t.cir %s
// RUN: FileCheck --input-file=%t.cir %s
// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -std=c++20 -O1 -fclangir -emit-llvm -fno-clangir-call-conv-lowering -o %t.ll %s
// RUN: FileCheck --input-file=%t.ll --check-prefix=LLVM %s
// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -std=c++20 -O1 -fclangir -emit-llvm -fno-clangir-call-conv-lowering -o %t-cir.ll %s
// RUN: FileCheck --input-file=%t-cir.ll --check-prefix=LLVM %s
// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -std=c++20 -O1 -emit-llvm -o %t.ll %s
// RUN: FileCheck --input-file=%t.ll --check-prefix=OGCG %s

struct Base1 {
virtual ~Base1();
Expand All @@ -16,26 +18,55 @@ struct Derived final : Base1 {};
Derived *ptr_cast(Base1 *ptr) {
return dynamic_cast<Derived *>(ptr);
// CHECK: %[[#SRC:]] = cir.load{{.*}} %{{.+}} : !cir.ptr<!cir.ptr<!rec_Base1>>, !cir.ptr<!rec_Base1>
// CHECK-NEXT: %[[#EXPECTED_VPTR:]] = cir.vtable.address_point(@_ZTV7Derived, address_point = <index = 0, offset = 2>) : !cir.vptr
// CHECK-NEXT: %[[#SRC_VPTR_PTR:]] = cir.cast bitcast %[[#SRC]] : !cir.ptr<!rec_Base1> -> !cir.ptr<!cir.vptr>
// CHECK-NEXT: %[[#SRC_VPTR:]] = cir.load{{.*}} %[[#SRC_VPTR_PTR]] : !cir.ptr<!cir.vptr>, !cir.vptr
// CHECK-NEXT: %[[#SUCCESS:]] = cir.cmp(eq, %[[#SRC_VPTR]], %[[#EXPECTED_VPTR]]) : !cir.vptr, !cir.bool
// CHECK-NEXT: %{{.+}} = cir.ternary(%[[#SUCCESS]], true {
// CHECK-NEXT: %[[#RES:]] = cir.cast bitcast %[[#SRC]] : !cir.ptr<!rec_Base1> -> !cir.ptr<!rec_Derived>
// CHECK-NEXT: cir.yield %[[#RES]] : !cir.ptr<!rec_Derived>
// CHECK-NEXT: %[[#SRC_IS_NONNULL:]] = cir.cast ptr_to_bool %[[#SRC]] : !cir.ptr<!rec_Base1> -> !cir.bool
// CHECK-NEXT: %[[#SRC_IS_NULL:]] = cir.unary(not, %[[#SRC_IS_NONNULL]]) : !cir.bool, !cir.bool
// CHECK-NEXT: %[[#RESULT:]] = cir.ternary(%4, true {
// CHECK-NEXT: %[[#NULL_DEST_PTR:]] = cir.const #cir.ptr<null> : !cir.ptr<!rec_Derived>
// CHECK-NEXT: cir.yield %[[#NULL_DEST_PTR]] : !cir.ptr<!rec_Derived>
// CHECK-NEXT: }, false {
// CHECK-NEXT: %[[#NULL:]] = cir.const #cir.ptr<null> : !cir.ptr<!rec_Derived>
// CHECK-NEXT: cir.yield %[[#NULL]] : !cir.ptr<!rec_Derived>
// CHECK-NEXT: %[[#EXPECTED_VPTR:]] = cir.vtable.address_point(@_ZTV7Derived, address_point = <index = 0, offset = 2>) : !cir.vptr
// CHECK-NEXT: %[[#SRC_VPTR_PTR:]] = cir.cast bitcast %[[#SRC]] : !cir.ptr<!rec_Base1> -> !cir.ptr<!cir.vptr>
// CHECK-NEXT: %[[#SRC_VPTR:]] = cir.load{{.*}} %[[#SRC_VPTR_PTR]] : !cir.ptr<!cir.vptr>, !cir.vptr
// CHECK-NEXT: %[[#SUCCESS:]] = cir.cmp(eq, %[[#SRC_VPTR]], %[[#EXPECTED_VPTR]]) : !cir.vptr, !cir.bool
// CHECK-NEXT: %[[#EXACT_RESULT:]] = cir.ternary(%[[#SUCCESS]], true {
// CHECK-NEXT: %[[#RES:]] = cir.cast bitcast %[[#SRC]] : !cir.ptr<!rec_Base1> -> !cir.ptr<!rec_Derived>
// CHECK-NEXT: cir.yield %[[#RES]] : !cir.ptr<!rec_Derived>
// CHECK-NEXT: }, false {
// CHECK-NEXT: %[[#NULL:]] = cir.const #cir.ptr<null> : !cir.ptr<!rec_Derived>
// CHECK-NEXT: cir.yield %[[#NULL]] : !cir.ptr<!rec_Derived>
// CHECK-NEXT: }) : (!cir.bool) -> !cir.ptr<!rec_Derived>
// CHECK-NEXT: cir.yield %[[#EXACT_RESULT]] : !cir.ptr<!rec_Derived>
// CHECK-NEXT: }) : (!cir.bool) -> !cir.ptr<!rec_Derived>
}

// LLVM: define dso_local ptr @_Z8ptr_castP5Base1(ptr readonly captures(ret: address, provenance) %[[#SRC:]])
// LLVM: define dso_local ptr @_Z8ptr_castP5Base1(ptr {{.*}} %[[#SRC:]])
// LLVM-NEXT: %[[SRC_IS_NULL:.*]] = icmp eq ptr %[[#SRC]], null
// LLVM-NEXT: br i1 %[[SRC_IS_NULL]], label %[[#LABEL_END:]], label %[[#LABEL_NONNULL:]]
// LLVM: [[#LABEL_NONNULL]]
// LLVM-NEXT: %[[#VPTR:]] = load ptr, ptr %[[#SRC]], align 8
// LLVM-NEXT: %[[#SUCCESS:]] = icmp eq ptr %[[#VPTR]], getelementptr inbounds nuw (i8, ptr @_ZTV7Derived, i64 16)
// LLVM-NEXT: %[[RESULT:.+]] = select i1 %[[#SUCCESS]], ptr %[[#SRC]], ptr null
// LLVM-NEXT: ret ptr %[[RESULT]]
// LLVM-NEXT: %[[EXACT_RESULT:.*]] = select i1 %[[#SUCCESS]], ptr %[[#SRC]], ptr null
// LLVM-NEXT: br label %[[#LABEL_END]]
// LLVM: [[#LABEL_END]]
// LLVM-NEXT: %[[#RESULT:]] = phi ptr [ %[[EXACT_RESULT]], %[[#LABEL_NONNULL]] ], [ null, %{{.*}} ]
// LLVM-NEXT: ret ptr %[[#RESULT]]
// LLVM-NEXT: }

// OGCG: define{{.*}} ptr @_Z8ptr_castP5Base1(ptr {{.*}} %[[SRC:.*]])
// OGCG-NEXT: entry:
// OGCG-NEXT: %[[NULL_CHECK:.*]] = icmp eq ptr %[[SRC]], null
// OGCG-NEXT: br i1 %[[NULL_CHECK]], label %[[LABEL_NULL:.*]], label %[[LABEL_NOTNULL:.*]]
// OGCG: [[LABEL_NOTNULL]]:
// OGCG-NEXT: %[[VTABLE:.*]] = load ptr, ptr %[[SRC]], align 8
// OGCG-NEXT: %[[VTABLE_CHECK:.*]] = icmp eq ptr %[[VTABLE]], getelementptr inbounds {{.*}} (i8, ptr @_ZTV7Derived, i64 16)
// OGCG-NEXT: br i1 %[[VTABLE_CHECK]], label %[[LABEL_END:.*]], label %[[LABEL_NULL]]
// OGCG: [[LABEL_NULL]]:
// OGCG-NEXT: br label %[[LABEL_END]]
// OGCG: [[LABEL_END]]:
// OGCG-NEXT: %[[RESULT:.*]] = phi ptr [ %[[SRC]], %[[LABEL_NOTNULL]] ], [ null, %[[LABEL_NULL]] ]
// OGCG-NEXT: ret ptr %[[RESULT]]
// OGCG-NEXT: }

Derived &ref_cast(Base1 &ref) {
return dynamic_cast<Derived &>(ref);
// CHECK: %[[#SRC:]] = cir.load{{.*}} %{{.+}} : !cir.ptr<!cir.ptr<!rec_Base1>>, !cir.ptr<!rec_Base1>
Expand All @@ -62,6 +93,18 @@ Derived &ref_cast(Base1 &ref) {
// LLVM-NEXT: ret ptr %[[#SRC]]
// LLVM-NEXT: }

// OGCG: define{{.*}} ptr @_Z8ref_castR5Base1(ptr {{.*}} %[[REF:.*]])
// OGCG-NEXT: entry:
// OGCG-NEXT: %[[VTABLE:.*]] = load ptr, ptr %[[REF]], align 8
// OGCG-NEXT: %[[VTABLE_CHECK:.*]] = icmp eq ptr %[[VTABLE]], getelementptr inbounds {{.*}} (i8, ptr @_ZTV7Derived, i64 16)
// OGCG-NEXT: br i1 %[[VTABLE_CHECK]], label %[[LABEL_END:.*]], label %[[LABEL_NULL:.*]]
// OGCG: [[LABEL_NULL]]:
// OGCG-NEXT: {{.*}}call void @__cxa_bad_cast()
// OGCG-NEXT: unreachable
// OGCG: [[LABEL_END]]:
// OGCG-NEXT: ret ptr %[[REF]]
// OGCG-NEXT: }

Derived *ptr_cast_always_fail(Base2 *ptr) {
return dynamic_cast<Derived *>(ptr);
// CHECK: %{{.+}} = cir.load{{.*}} %{{.+}} : !cir.ptr<!cir.ptr<!rec_Base2>>, !cir.ptr<!rec_Base2>
Expand Down
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