[clang] 4d4088e - [CIR] Add support for dynamic cast to void (#162905)
via cfe-commits
cfe-commits at lists.llvm.org
Thu Oct 16 17:07:18 PDT 2025
Author: Andy Kaylor
Date: 2025-10-16T17:07:14-07:00
New Revision: 4d4088e2ce96f84c8c317d1a2bca55f871726860
URL: https://github.com/llvm/llvm-project/commit/4d4088e2ce96f84c8c317d1a2bca55f871726860
DIFF: https://github.com/llvm/llvm-project/commit/4d4088e2ce96f84c8c317d1a2bca55f871726860.diff
LOG: [CIR] Add support for dynamic cast to void (#162905)
This adds the support for dynamic cast to void in the Itanium ABI.
Added:
Modified:
clang/include/clang/CIR/Dialect/Builder/CIRBaseBuilder.h
clang/lib/CIR/CodeGen/CIRGenBuilder.h
clang/lib/CIR/CodeGen/CIRGenItaniumCXXABI.cpp
clang/lib/CIR/Dialect/Transforms/LoweringPrepareItaniumCXXABI.cpp
clang/test/CIR/CodeGen/dynamic-cast.cpp
Removed:
################################################################################
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 84acc74ccf0f5..50d585dca3b8c 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 1b85a530cbdd7..d54d2e9cb29e5 100644
--- a/clang/lib/CIR/CodeGen/CIRGenItaniumCXXABI.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenItaniumCXXABI.cpp
@@ -1945,6 +1945,15 @@ 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,
@@ -1979,10 +1988,8 @@ 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 ptr
diff Ty = targetInfo.getPtrDiffType(clang::LangAS::Default);
+ bool ptr
diff TyIsSigned = clang::TargetInfo::isTypeSigned(ptr
diff Ty);
+ uint64_t ptr
diff TyWidth = targetInfo.getTypeWidth(ptr
diff Ty);
+
+ vtableElemTy = cir::IntType::get(builder.getContext(), ptr
diff TyWidth,
+ ptr
diff TyIsSigned);
+ 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]] ]
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