https://github.com/mmha created https://github.com/llvm/llvm-project/pull/159162
This patch enables calling virtual functions of virtual base classes of a
derived class.
>From a25ee7f9df6eb7c5d6b237eb5b072c182b4f0681 Mon Sep 17 00:00:00 2001
From: Morris Hafner <mhaf...@nvidia.com>
Date: Mon, 8 Sep 2025 16:38:50 +0200
Subject: [PATCH] [CIR] Add virtual base support to getAddressOfBaseClass
This patch enables calling virtual functions of virtual base classes of a
derived class.
---
clang/lib/CIR/CodeGen/CIRGenClass.cpp | 42 +++++++++-----
clang/test/CIR/CodeGen/vbase.cpp | 82 ++++++++++++++++++++++++++-
2 files changed, 110 insertions(+), 14 deletions(-)
diff --git a/clang/lib/CIR/CodeGen/CIRGenClass.cpp
b/clang/lib/CIR/CodeGen/CIRGenClass.cpp
index 0a8dc2b62fe21..08fdfad899a60 100644
--- a/clang/lib/CIR/CodeGen/CIRGenClass.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenClass.cpp
@@ -865,28 +865,37 @@ Address CIRGenFunction::getAddressOfBaseClass(
bool nullCheckValue, SourceLocation loc) {
assert(!path.empty() && "Base path should not be empty!");
+ CastExpr::path_const_iterator start = path.begin();
+ const CXXRecordDecl *vBase = nullptr;
+
if ((*path.begin())->isVirtual()) {
- // The implementation here is actually complete, but let's flag this
- // as an error until the rest of the virtual base class support is in
place.
- cgm.errorNYI(loc, "getAddrOfBaseClass: virtual base");
- return Address::invalid();
+ vBase = (*start)->getType()->castAsCXXRecordDecl();
+ ++start;
}
// Compute the static offset of the ultimate destination within its
// allocating subobject (the virtual base, if there is one, or else
// the "complete" object that we see).
- CharUnits nonVirtualOffset =
- cgm.computeNonVirtualBaseClassOffset(derived, path);
+ CharUnits nonVirtualOffset = cgm.computeNonVirtualBaseClassOffset(
+ vBase ? vBase : derived, {start, path.end()});
+
+ // If there's a virtual step, we can sometimes "devirtualize" it.
+ // For now, that's limited to when the derived type is final.
+ // TODO: "devirtualize" this for accesses to known-complete objects.
+ if (vBase && derived->hasAttr<FinalAttr>()) {
+ const ASTRecordLayout &layout = getContext().getASTRecordLayout(derived);
+ CharUnits vBaseOffset = layout.getVBaseClassOffset(vBase);
+ nonVirtualOffset += vBaseOffset;
+ vBase = nullptr; // we no longer have a virtual step
+ }
// Get the base pointer type.
mlir::Type baseValueTy = convertType((path.end()[-1])->getType());
assert(!cir::MissingFeatures::addressSpace());
- // The if statement here is redundant now, but it will be needed when we add
- // support for virtual base classes.
// If there is no virtual base, use cir.base_class_addr. It takes care of
// the adjustment and the null pointer check.
- if (nonVirtualOffset.isZero()) {
+ if (nonVirtualOffset.isZero() && !vBase) {
assert(!cir::MissingFeatures::sanitizers());
return builder.createBaseClassAddr(getLoc(loc), value, baseValueTy, 0,
/*assumeNotNull=*/true);
@@ -894,10 +903,17 @@ Address CIRGenFunction::getAddressOfBaseClass(
assert(!cir::MissingFeatures::sanitizers());
- // Apply the offset
- value = builder.createBaseClassAddr(getLoc(loc), value, baseValueTy,
- nonVirtualOffset.getQuantity(),
- /*assumeNotNull=*/true);
+ // Compute the virtual offset.
+ mlir::Value virtualOffset = nullptr;
+ if (vBase) {
+ virtualOffset = cgm.getCXXABI().getVirtualBaseClassOffset(
+ getLoc(loc), *this, value, derived, vBase);
+ }
+
+ // Apply both offsets.
+ value = applyNonVirtualAndVirtualOffset(
+ getLoc(loc), *this, value, nonVirtualOffset, virtualOffset, derived,
+ vBase, baseValueTy, not nullCheckValue);
// Cast to the destination type.
value = value.withElementType(builder, baseValueTy);
diff --git a/clang/test/CIR/CodeGen/vbase.cpp b/clang/test/CIR/CodeGen/vbase.cpp
index 91396518a40b0..4d57f8ea74e0c 100644
--- a/clang/test/CIR/CodeGen/vbase.cpp
+++ b/clang/test/CIR/CodeGen/vbase.cpp
@@ -13,19 +13,29 @@ class Base {
class Derived : public virtual Base {};
-// This is just here to force the record types to be emitted.
void f() {
Derived d;
+ d.f();
+}
+
+class DerivedFinal final : public virtual Base {};
+
+void g() {
+ DerivedFinal df;
+ df.f();
}
// CIR: !rec_Base = !cir.record<class "Base" {!cir.vptr}>
// CIR: !rec_Derived = !cir.record<class "Derived" {!rec_Base}>
+// CIR: !rec_DerivedFinal = !cir.record<class "DerivedFinal" {!rec_Base}>
// LLVM: %class.Derived = type { %class.Base }
// LLVM: %class.Base = type { ptr }
+// LLVM: %class.DerivedFinal = type { %class.Base }
// OGCG: %class.Derived = type { %class.Base }
// OGCG: %class.Base = type { ptr }
+// OGCG: %class.DerivedFinal = type { %class.Base }
// Test the constructor handling for a class with a virtual base.
struct A {
@@ -47,6 +57,76 @@ void ppp() { B b; }
// OGCG: @_ZTV1B = linkonce_odr unnamed_addr constant { [3 x ptr] } { [3 x
ptr] [ptr inttoptr (i64 12 to ptr), ptr null, ptr @_ZTI1B] }, comdat, align 8
+// CIR: cir.func {{.*}}@_Z1fv() {
+// CIR: %[[D:.+]] = cir.alloca !rec_Derived, !cir.ptr<!rec_Derived>, ["d",
init]
+// CIR: cir.call @_ZN7DerivedC1Ev(%[[D]]) nothrow : (!cir.ptr<!rec_Derived>)
-> ()
+// CIR: %[[VPTR_PTR:.+]] = cir.vtable.get_vptr %[[D]] :
!cir.ptr<!rec_Derived> -> !cir.ptr<!cir.vptr>
+// CIR: %[[VPTR:.+]] = cir.load {{.*}} %[[VPTR_PTR]] : !cir.ptr<!cir.vptr>,
!cir.vptr
+// CIR: %[[VPTR_I8:.+]] = cir.cast(bitcast, %[[VPTR]] : !cir.vptr),
!cir.ptr<!u8i>
+// CIR: %[[NEG32:.+]] = cir.const #cir.int<-32> : !s64i
+// CIR: %[[ADJ_VPTR_I8:.+]] = cir.ptr_stride(%[[VPTR_I8]] : !cir.ptr<!u8i>,
%[[NEG32]] : !s64i), !cir.ptr<!u8i>
+// CIR: %[[OFFSET_PTR:.+]] = cir.cast(bitcast, %[[ADJ_VPTR_I8]] :
!cir.ptr<!u8i>), !cir.ptr<!s64i>
+// CIR: %[[OFFSET:.+]] = cir.load {{.*}} %[[OFFSET_PTR]] : !cir.ptr<!s64i>,
!s64i
+// CIR: %[[D_I8:.+]] = cir.cast(bitcast, %[[D]] : !cir.ptr<!rec_Derived>),
!cir.ptr<!u8i>
+// CIR: %[[ADJ_THIS_I8:.+]] = cir.ptr_stride(%[[D_I8]] : !cir.ptr<!u8i>,
%[[OFFSET]] : !s64i), !cir.ptr<!u8i>
+// CIR: %[[ADJ_THIS_D:.+]] = cir.cast(bitcast, %[[ADJ_THIS_I8]] :
!cir.ptr<!u8i>), !cir.ptr<!rec_Derived>
+// CIR: %[[BASE_THIS:.+]] = cir.cast(bitcast, %[[ADJ_THIS_D]] :
!cir.ptr<!rec_Derived>), !cir.ptr<!rec_Base>
+// CIR: %[[BASE_VPTR_PTR:.+]] = cir.vtable.get_vptr %[[BASE_THIS]] :
!cir.ptr<!rec_Base> -> !cir.ptr<!cir.vptr>
+// CIR: %[[BASE_VPTR:.+]] = cir.load {{.*}} %[[BASE_VPTR_PTR]] :
!cir.ptr<!cir.vptr>, !cir.vptr
+// CIR: %[[SLOT_PTR:.+]] = cir.vtable.get_virtual_fn_addr %[[BASE_VPTR]][0]
: !cir.vptr -> !cir.ptr<!cir.ptr<!cir.func<(!cir.ptr<!rec_Base>)>>>
+// CIR: %[[FN:.+]] = cir.load {{.*}} %[[SLOT_PTR]] :
!cir.ptr<!cir.ptr<!cir.func<(!cir.ptr<!rec_Base>)>>>,
!cir.ptr<!cir.func<(!cir.ptr<!rec_Base>)>>
+// CIR: cir.call %[[FN]](%[[BASE_THIS]]) :
(!cir.ptr<!cir.func<(!cir.ptr<!rec_Base>)>>, !cir.ptr<!rec_Base>) -> ()
+// CIR: cir.return
+
+// CIR: cir.func {{.*}}@_Z1gv() {
+// CIR: %[[DF:.+]] = cir.alloca !rec_DerivedFinal,
!cir.ptr<!rec_DerivedFinal>, ["df", init]
+// CIR: cir.call @_ZN12DerivedFinalC1Ev(%[[DF]]) nothrow :
(!cir.ptr<!rec_DerivedFinal>) -> ()
+// CIR: %[[BASE_THIS_2:.+]] = cir.base_class_addr %[[DF]] :
!cir.ptr<!rec_DerivedFinal> nonnull [0] -> !cir.ptr<!rec_Base>
+// CIR: %[[BASE_VPTR_PTR_2:.+]] = cir.vtable.get_vptr %[[BASE_THIS_2]] :
!cir.ptr<!rec_Base> -> !cir.ptr<!cir.vptr>
+// CIR: %[[BASE_VPTR_2:.+]] = cir.load {{.*}} %[[BASE_VPTR_PTR_2]] :
!cir.ptr<!cir.vptr>, !cir.vptr
+// CIR: %[[SLOT_PTR_2:.+]] = cir.vtable.get_virtual_fn_addr
%[[BASE_VPTR_2]][0] : !cir.vptr ->
!cir.ptr<!cir.ptr<!cir.func<(!cir.ptr<!rec_Base>)>>>
+// CIR: %[[FN_2:.+]] = cir.load {{.*}} %[[SLOT_PTR_2]] :
!cir.ptr<!cir.ptr<!cir.func<(!cir.ptr<!rec_Base>)>>>,
!cir.ptr<!cir.func<(!cir.ptr<!rec_Base>)>>
+// CIR: cir.call %[[FN_2]](%[[BASE_THIS_2]]) :
(!cir.ptr<!cir.func<(!cir.ptr<!rec_Base>)>>, !cir.ptr<!rec_Base>) -> ()
+// CIR: cir.return
+
+// LLVM: define {{.*}}void @_Z1fv()
+// LLVM: %[[D:.+]] = alloca {{.*}}
+// LLVM: call void @_ZN7DerivedC1Ev(ptr %[[D]])
+// LLVM: %[[VPTR_ADDR:.+]] = load ptr, ptr %[[D]]
+// LLVM: %[[NEG32_PTR:.+]] = getelementptr i8, ptr %[[VPTR_ADDR]], i64 -32
+// LLVM: %[[OFF:.+]] = load i64, ptr %[[NEG32_PTR]]
+// LLVM: %[[ADJ_THIS:.+]] = getelementptr i8, ptr %[[D]], i64 %[[OFF]]
+// LLVM: %[[VFN_TAB:.+]] = load ptr, ptr %[[ADJ_THIS]]
+// LLVM: %[[SLOT0:.+]] = getelementptr inbounds ptr, ptr %[[VFN_TAB]], i32 0
+// LLVM: %[[VFN:.+]] = load ptr, ptr %[[SLOT0]]
+// LLVM: call void %[[VFN]](ptr %[[ADJ_THIS]])
+// LLVM: ret void
+
+// LLVM: define {{.*}}void @_Z1gv()
+// LLVM: %[[DF:.+]] = alloca {{.*}}
+// LLVM: call void @_ZN12DerivedFinalC1Ev(ptr %[[DF]])
+// LLVM: %[[VPTR2:.+]] = load ptr, ptr %[[DF]]
+// LLVM: %[[SLOT0_2:.+]] = getelementptr inbounds ptr, ptr %[[VPTR2]], i32 0
+// LLVM: %[[VFN2:.+]] = load ptr, ptr %[[SLOT0_2]]
+// LLVM: call void %[[VFN2]](ptr %[[DF]])
+// LLVM: ret void
+
+// OGCG: define {{.*}}void @_Z1fv()
+// OGCG: %[[D:.+]] = alloca {{.*}}
+// OGCG: call void @_ZN7DerivedC1Ev(ptr {{.*}} %[[D]])
+// OGCG: %[[VTABLE:.+]] = load ptr, ptr %[[D]]
+// OGCG: %[[NEG32_PTR:.+]] = getelementptr i8, ptr %[[VTABLE]], i64 -32
+// OGCG: %[[OFF:.+]] = load i64, ptr %[[NEG32_PTR]]
+// OGCG: %[[ADJ_THIS:.+]] = getelementptr inbounds i8, ptr %[[D]], i64
%[[OFF]]
+// OGCG: call void @_ZN4Base1fEv(ptr {{.*}} %[[ADJ_THIS]])
+// OGCG: ret void
+
+// OGCG: define {{.*}}void @_Z1gv()
+// OGCG: %[[DF:.+]] = alloca {{.*}}
+// OGCG: call void @_ZN12DerivedFinalC1Ev(ptr {{.*}} %[[DF]])
+// OGCG: call void @_ZN4Base1fEv(ptr {{.*}} %[[DF]])
+// OGCG: ret void
+
// Constructor for B
// CIR: cir.func comdat linkonce_odr @_ZN1BC1Ev(%arg0: !cir.ptr<!rec_B>
// CIR: %[[THIS_ADDR:.*]] = cir.alloca !cir.ptr<!rec_B>,
!cir.ptr<!cir.ptr<!rec_B>>, ["this", init]
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